ACI 122R-14: Guide to Thermal Properties of Concrete and ... · This guide reports data on the thermal properties of concrete and masonry constituents, masonry units, and systems

Guide to Thermal Properties of Concrete and Masonry SystemsReported by ACI/TMS Committee 122

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First PrintingDecember 2014

ISBN: 978-0-87031-971-6

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Guide to Thermal Properties of Concrete and Masonry Systems

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This guide reports data on the thermal properties of concrete and masonry constituents, masonry units, and systems of mate-rials and products that form building components. This guide includes consideration of thermal inertia of concrete and masonry, passive solar design, and procedures to limit condensation within assemblages.

Keywords: aggregate; cement paste; concrete masonry unit; moisture; precast/prestressed concrete; specific heat; sustainability; thermal conduc-tivity; thermal diffusivity; thermal resistance.

CONTENTS

CHAPTER 1—INTRODUCTION, p. 21.1—Introduction, p. 21.2—Energy conservation with concrete and masonry, p. 21.3—Building enclosure requirements, p. 2

CHAPTER 2—NOTATION AND DEFINITIONS, p. 22.1—Notation, p. 22.2—Definitions, p. 3

CHAPTER 3—THERMAL CONDUCTIVITY OF CONCRETE, AGGREGATE, AND CEMENT PASTE, p. 4

3.1—Introduction, p. 43.2—Thermal conductivity of concrete, p. 43.3—Influence of moisture, p. 43.4—Thermal conductivity of aggregates and cement

paste, p. 53.5—Thermal conductivity of concrete used in concrete

masonry units, p. 53.6—Thermal conductivity of two-phase systems, p. 73.7—Sample thermal conductivity calculations using

cubic model, p. 73.8—Practical thermal conductivity, p. 8

CHAPTER 4—CALCULATION METHODS FOR STEADY-STATE THERMAL RESISTANCE OF WALL SYSTEMS, p. 9

4.1—Introduction, p. 94.2—Thermal resistance of concrete masonry walls, p. 104.3—Methods for calculating thermal resistance of

concrete masonry units, p. 104.4—Thermal resistance of other concrete wall systems,

p. 13

CHAPTER 5—THERMAL INERTIA, p. 165.1—Introduction, p. 165.2—Factors affecting thermal inertia effect, p. 165.3—Determining thermal inertia effects, p. 195.4—Equivalent R-values for concrete and masonry walls,

p. 21

Stephen S. Szoke, Chair

ACI 122R-14

Guide to Thermal Properties of Concrete and Masonry Systems

Reported by ACI/TMS Committee 122

Maribeth S. BradfieldTheodore W. Bremner

Dennis W. Graber

Thomas A. HolmJohn P. Ries

Jeffrey F. Speck

Martha G. VanGeem Consulting MemberW. Calvin McCall

ACI Committee Reports, Guides, and Commentaries are intended for guidance in planning, designing, executing, and inspecting construction. This document is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. The American Concrete Institute disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising therefrom.

Reference to this document shall not be made in contract documents. If items found in this document are desired by the Architect/Engineer to be a part of the contract documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer.

ACI 122R-14 supersedes ACI 122R-02 and was adopted and published December 2014..

Copyright © 2014, American Concrete InstituteAll rights reserved including rights of reproduction and use in any form or by any

means, including the making of copies by any photo process, or by electronic or mechanical device, printed, written, or oral, or recording for sound or visual reproduc-tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.

1Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=University of Texas Revised Sub Account/5620001114


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5.5—Interior thermal inertia, p. 21

CHAPTER 6—THERMAL PROPERTIES FOR PASSIVE SOLAR DESIGN, p. 22

6.1—Introduction, p. 226.2—Thermal properties, p. 236.3—Incorporating mass into passive solar designs, p. 236.4—Summary, p. 24

CHAPTER 7—CONDENSATION CONTROL, p. 247.1—Introduction, p. 247.2—Prevention of condensation on wall surfaces under

steady-state analysis, p. 257.3—Prevention of condensation within wall construc-

tions, p. 25

CHAPTER 8—REFERENCES, p. 26Authored documents, p. 27

APPENDIX A—TEST RESULTS AND CALCULATED THERMAL CONDUCTANCE OF OVEN-DRIED CONCRETE MASONRY, p. 29

CHAPTER 1—INTRODUCTION

1.1—IntroductionTo reduce the use of nonrecoverable energy sources,

authorities have adopted energy-conservation building codes and standards that apply to the design and construc-tion of buildings. The design of energy-conserving buildings requires an expanded understanding of the thermal proper-ties of the building envelope and the materials that comprise the envelope system.

This guide provides thermal-property data and design techniques that are useful in designing concrete and masonry building envelopes and determining energy code compli-ance. The guide is intended for use by owners, architects, engineers, building inspectors, code-enforcement officials, and all those interested in the energy-efficient design of buildings containing concrete or masonry components.

1.2—Energy conservation with concrete and masonry

Due to its inherent functionality and the availability of raw materials used in production, concrete and masonry are the world’s most widely used building materials. Many civiliza-tions have built structures with concrete and masonry walls that provide uniform and comfortable indoor temperatures despite all types of climatic conditions. Cathedrals composed of massive masonry walls produce an indoor climate with little temperature variation during the entire year despite the absence of a heating system. Even primitive housing in the desert areas of North America used thick masonry walls that resulted in acceptable interior temperatures despite high outside daytime temperatures.

Housing systems have been developed featuring effi-cient load-bearing concrete or masonry wall systems that provide resistance to weather, temperature changes, fire,

and noise. Many of these wall systems are made with light-weight concrete to enhance both static and dynamic thermal resistance.

Numerous organizations have studied and reported on the steady-state and dynamic energy-conserving contribu-tions that concrete and concrete masonry walls can make to thermal efficiency in buildings (Peavy et al. 1973; Petersen and Barnett 1980; Petersen et al. 1981; U.S. Department of Energy 1989; ASHRAE 2009; ANSI/ASHRAE/IES 90.1; Childs et al. 1983; National Concrete Masonry Associa-tion 2010; Portland Cement Association 1981, 1982). This increased energy efficiency may permit reductions in the required size and operating costs of mechanical systems. This reduction in energy usage is not recognized by steady-state calculations (R-values and U-values). Improved calcu-lation methods are required to account for the dynamic, real-world performance of concrete and concrete masonry building elements.

1.3—Building enclosure requirementsIn addition to structural requirements, a building envelope

should be designed to control the flow of air, heat, sunlight, radiant energy, liquid water, and water vapor. It should also provide the many other attributes generally associated with enclosure materials, including fire protection, noise control, impact damage resistance, durability, aesthetic quality, and economy. Analysis of building enclosure materials should extend beyond heat-flow analysis to also account for their multifunctional purposes. The non-heat-flow subjects are beyond the scope of this guide, but this exclusion should not be taken as an indication that they are not crucial to the total overall performance of a building enclosure.

CHAPTER 2—NOTATION AND DEFINITIONS

2.1—Notationa = fractional areaagr = fractional grouted area of wallai = fractional area of insulationanp = fractional area of heat flow path for path number p

of thermal layer number nas = fractional area of steelaungr = fractional ungrouted area of wallaw = fractional area of web of masonry unit determined

using the dimensions of web in the same planes as the height and length of the masonry unit

C = thermal conductance, Btu/(h·ft2·°F) (W/(m2·K))cp = specific heat, Btu/(lb·°F) (J/kg·K)fs = face shell thickness of concrete masonry unit, in.

(mm)hc = heat capacity, Btu(ft3·°F) (J/(m3·K))I = thermal inertia, Btu/(h1/2·ft2·°F) (J/(m2·K·s1/2))kc = thermal conductivity of concrete, Btu · in./(h·ft2·°F)

(W/(m·K))kf = thermal conductivity of material placed in the cores

of masonry units, Btu·in./(h·ft2·°F) (W/(m·K))kp = thermal conductivity of cement paste, Btu·in./

(h·ft2·°F) (W/(m·K))

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2 GUIDE TO THERMAL PROPERTIES OF CONCRETE AND MASONRY SYSTEMS (ACI 122R-14)



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k = thermal conductivity, Btu·in./(h·ft2·°F) (W/(m·K))L = linear dimension, in. or ft (mm or m)La = actual length, in. (mm)Lb = width of concrete masonry unit, in. (mm)M = water-vapor permeance, permq = heat flow rate, Btu/h (W/K)qss = heat flow rate when steady-state conditions are

achieved, Btu/h (W/K)qw = heat flow rate for conditions other than steady-

state, Btu/h (W/K)R orR-value = thermal resistance, (h·ft2·°F)/Btu ((m2·K)/W))Ri = thermal resistance of interior surface-air-film, equal

to 0.68 (h·ft2·°F)/Btu (0.120 m2·K/W) for nonre-flective, still air, vertical surfaces with horizontal heat flow

Rin = thermal resistance of insulation, (h·ft2·°F)/Btu ((m2·K)/W)

Rnp = thermal resistance of heat flow path number p of thermal layer number n, (h·ft2·°F)/Btu ((m2·K)/W))

Ro = thermal resistance of exterior surface-air-film, equal to 0.17 (h·ft2·°F)/Btu for 15 mph wind (0.030 m2·K/W for 6.7 m/s wind)

Rs = thermal resistance of steel, (h·ft2·°F)/Btu ((m2·K)/W)

RT = total thermal resistance of a construction assembly including the thermal resistance of interior and exte-rior surface air-films, (h·ft2·°F)/Btu ((m2·K)/W))

Rt = thermal resistance of the insulating layer, (h·ft2·°F)/Btu ((m2·K)/W)

ti = indoor air temperature, °F (°C)to = outdoor air temperature, °F (°C)ts = saturation, or dew point temperature, °F (°C)U orU-value = overall coefficient of thermal transmittance, Btu/

(h·ft2·°F) (W/(m2·K))Ugr = overall coefficient of thermal transmittance of fully

grouted wall, Btu/(h·ft2·°F) (W/m2·K)Uungr = overall coefficient of thermal transmittance of

ungrouted wall, Btu/(h·ft2·°F) (W/m2·K)V = volume, ft3 (m3)Va = volume of compacted aggregate, ft3 (m3)Vc = volume of cement paste, ft3 (m3)w = web thickness measured perpendicular to face of

masonry unit, in (mm)α = thermal diffusivity, (in.·ft)/h (m2/s)μ = water-vapor permeability, gr·in./(h·ft2·in.-Hg) (Hg/

(s·m·Pa))ρ = density, lb/ft3 (kg/m3) – specific property of a gas,

liquid, or solid is a measure of the mass per unit volume

ρm = moist density, lb/ft3 (kg/m3) – density of a material where moisture is present

ρo = oven-dry density, lb/ft3 (kg/m3)

2.2—DefinitionsACI provides a comprehensive list of definitions through

an online resource, “ACI Concrete Terminology,” http://www.concrete.org/Tools/ConcreteTerminology.aspx. Defi-nitions provided herein complement that resource.

heat capacity––measure of the amount of heat required to change by one degree a specified object.

moist density––density of a material where moisture is present.

overall coefficient of thermal transmittance, U––heat transfer of a construction assembly is determined by combining the thermal resistance of the interior and exterior surface-air-films with the combined thermal resistance of the total construction materials.

solar reflectance—surface property of a material deter-mined as the ratio of the reflected solar radiation, or electro-magnetic flux, to the incident solar radiation measured on a scale of 0.0 to 1.0: from not reflective at 0.0 to 100 percent reflective at 1.0.

solar reflectance index—calculated representation of a material’s surface solar reflectance and emittance using temperature rise to represent the ability of a surface to reflect solar heat.

specific heat––measure of the amount of heat required to change by one degree a specified unit of mass of a gas, liquid, of solid.

thermal conductance––of a gas, liquid, or solid is a measure of the rate at which heat (energy) passes perpendic-ularly through a unit area of material of specified thickness for a temperature difference of one degree.

thermal conductivity––measure of the rate at which heat (energy) passes perpendicularly through a unit area of ther-mally homogeneous gas, liquid, or solid of unit thickness for a temperature difference of one degree under steady-state conditions.

thermal diffusivity––measure of the time rate of change of temperature at any point within a gas, liquid, or solid; thermal diffusivity is thermal conductivity divided by the product of density and specific heat, k/(ρ × cp).

thermal inertia––thermal inertia is a mathematical repre-sentation of the rate of temperature variation of gas, liquid, or solid subjected to heat (energy); thermal inertia is the square root of the product of thermal conductivity, density, and specific heat, (k × ρ × cp)0.5.

thermal resistance—the reciprocal of thermal conduc-tance expressed by the symbol R.

water-vapor permeability––the rate of water-vapor transmission per unit area of a material induced by a unit pressure difference between two specified parallel surfaces under specified temperature and humidity conditions; permeability is a property of a material and is the arithmetic product of permeance and thickness.

water-vapor permeance M—the rate of water-vapor transmission per unit area of a material or construction induced by a unit vapor pressure difference between two specified parallel surfaces under specified temperature and humidity conditions, in units of perm.


GUIDE TO THERMAL PROPERTIES OF CONCRETE AND MASONRY SYSTEMS (ACI 122R-14) 3



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http://www.concrete.org/Tools/ConcreteTerminology.aspx

http://www.concrete.org/Tools/ConcreteTerminology.aspx

CHAPTER 3—THERMAL CONDUCTIVITY OF CONCRETE, AGGREGATE, AND CEMENT PASTE

3.1—IntroductionMany factors influence the thermal conductivity of

concrete and concrete products. The thermal properties of concrete are influenced by the thermal properties and amounts of cement paste and aggregates, and the pres-ence of moisture. Further, the overall thermal conductance of nonmonolithic concrete elements is influenced by the product configuration.

3.2—Thermal conductivity of concreteThe measured thermal conductivity of a material, such

as concrete or insulation, is usually determined in accor-dance with ASTM C177 or C1363. Results of many such measurements have been tabulated by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE 2009). Several methods for calculating concrete thermal conductivity have been developed. These calculated estimates are useful because the nearly infinite combina-tions of ingredients in concrete make it nearly impossible to generate test data for all concrete and concrete products.

Basic testing programs demonstrate that, in general, the coefficient of thermal conductivity for concrete, kc, is depen-dent on the aggregate types used in the concrete mixture. For simplicity, these data are often correlated to concrete density ρ (Kluge et al. 1949; Price and Cordon 1949; Rowley and Algren 1937). Valore (1980) plotted oven-dry density of concrete as a function of the logarithm of kc, developing a straight line that can be expressed by the equation

kc = 0.5e0.02ρ (in.-lb units) (3.2) kc = 0.072e0.00125ρ (SI units)

Thermal conductivity values for concretes with the same density made with different aggregates can differ from the relationship expressed by Eq. (3.2) and may significantly underestimate kc for some normalweight concretes and for some lightweight concretes containing normalweight supplemental aggregates (Valore 1980, 1988). This is due to differences in the thermal properties of specific mineral types in the aggregates. Thermal conductivity values obtained using Eq. (3.2) for concretes with densities from 20 to 100 lb/ft3 (320 to 1600 kg/m3) correlate better to test data than for concretes outside this density range (Valore 1980). Oven-dry thermal conductivity values for several concretes made with various aggregates, as well as mortar and brick, are shown in Tables 3.2a and 3.2b. These values are based on linear regression equations developed from test data (Arnold 1969; Granholm 1961; Campbell-Allen and Thorn 1963; Institution of Heating and Ventilating Engineers 1975; Lentz and Monfore 1965a; Lewicki 1967; Petersen 1949; Valore 1958, 1988; Valore and Green 1951; Zoldners 1971).

3.3—Influence of moistureIn normal use, concrete is not in moisture-free or oven-dry

conditions; thus, concrete conductivity should be corrected for moisture effects (Valore 1958; Plonski 1973a,b; Tye and Spinney 1976). Table 3.3 lists correction factors to adjust oven-dry-concrete thermal conductivities to practical design

Table 3.2a—Thermal conductivity of oven-dry lightweight concrete, mortar, and brick (in.-lb units)*

Thermal conductivity kc, Btu·in./(h·ft2·°F)

Material, type of aggregate in concrete or data source

Oven-dry density, lb/ft3

15 20 25 30 40 50 60 70 80 90 100 110 120 130 140 150

Equation (3.2) kc = 0.5e0.02ρ 0.67 0.75 0.82 0.91 1.11 1.36 1.66 2.03 2.48 3.02 3.69 4.51 5.51 6.75 8.22 10.04

Neat cement paste and foam concrete 0.54 0.64 0.75 0.87 1.11 1.39 1.69 2.03 2.41 2.82 3.29 3.80 4.36 — — —

Autoclaved aerated (cellular) concrete 0.47 0.57 0.67 0.79 1.05 1.34 1.68 2.06 — — — — — — — —

Autoclaved microporous silica 0.41 0.51 0.61 0.72 0.96 1.25 1.58 1.95 2.38 — — — — — — —

Expanded polystyrene beads 0.50 0.62 0.74 0.88 1.18 1.53 1.94 — — — — — — — — —

Expanded perlite 0.46 0.57 0.69 0.83 1.13 1.48 1.90 — — — — — — — — —

Exfoliated vermiculite 0.53 0.63 0.74 0.86 1.10 1.38 1.69 — — — — — — — — —

Natural pumice — — — 0.74 1.02 1.35 1.73 2.19 2.71 3.32 4.03 — — — — —

Sintered fly ash and coal cinders — — — — — — 1.17 2.11 2.56 3.06 3.64 4.28 — — — —

Volcanic slag and scoria — — — — — — 1.67 2.06 2.50 2.99 3.56 — — — — —

Expanded slag — — — — — — 1.51 1.84 2.21 2.63 3.10 3.62 4.19 — — —

Expanded and sintered clay, shale, and slate — — — 0.87 1.16 1.49 1.88 2.23 2.83 3.40 4.05 4.78 — — — —

Sanded expanded clay, shale, and slate — — — — — 1.70 2.21 2.81 3.51 4.32 5.26 6.35 7.60 — — —

No-fines pumice, and expanded and sintered clay, shale, and slate — — — 0.97 1.27 1.60 1.98 2.40 2.88 3.41 — — — — — —

Limestone — — — — — — — 2.57 3.20 3.94 4.79 5.76 6.88 8.16 9.62 11.27

Cement-sand mortar and foam concrete — — — — — — 2.35 2.98 3.72 4.58 5.58 6.73 8.05 — — —

Fired clay bricks — — — — — — — 2.19 2.62 3.09 3.63 4.22 4.87 5.58 6.39 7.26*Obtained from density/thermal conductivity linear equations.





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values. Data in Table 3.3 may be used to estimate kc values for in-service concrete and concrete masonry elements.

A more accurate value to determine moisture effects may be estimated by increasing the value of kc by 6 percent for each 1 percent of moisture content by mass (Valore 1980, 1988).

kc (corrected) = kc × [1 + 6(ρm – ρo)/ρo] (3.3a)

For most concrete walls, a single factor of 1.2 can be applied to oven-dry kc values (Valore 1980). Therefore, the constant in Eq. (3.2) is changed from 0.500 (0.072) to 0.600 (0.087) to provide for a 20 percent increase in kc for air-dry, in-service, concrete or concrete masonry.

kc = 0.600e0.02ρ (in.-lb units) (3.3b) kc = 0.087e0.00125ρ (SI units)

3.4—Thermal conductivity of aggregates and cement paste

Tables 3.4a and 3.4b list conductivity values for some natural minerals used as concrete aggregates. Figure 3.4shows calculated thermal conductivity values for air-dry hardened cement pastes, kp (Valore 1980). These values are in good agreement with experimental values (Tyner 1946; Spooner 1977) for pastes with fi ve water-cementitious mate-

rial ratios (w/cm) ranging from 0.47 to 0.95. Experimental values averaged approximately 5 percent lower than calcu-lated values for pastes with w/cm in the range of 0.47 to 0.95, and 16 percent lower for paste with 0.35 w/cm. Lentz and Monfore (1965b) showed that conductivity kp for mature pastes in a moist-cured condition with w/cm of 0.4, 0.5, and 0.6 agreed within 2 percent of those calculated by Eq. (3.2) when corrected to an oven-dry condition. The value for a 0.32 w/cm paste, however, differed from the Eq. (3.2) value by approximately 20 percent.

3.5—Thermal conductivity of concrete used in concrete masonry units

Concrete masonry units (CMU) usually consist of approxi-mately 65 to 70 percent aggregate by volume. The remaining volume consists of voids between aggregate particles, entrapped air, and cement paste. The typical air-void content of concrete used to make lightweight CMU, for example, has been found to be 8 to 12 percent by volume. Expressed as a percentage of the cement paste, void volumes are approxi-mately 25 to 40 percent. For a typical lightweight CMU having a net w/cm of 0.6 and an average cement-paste air-void content of 40 percent, the thermal conductivity is in the range of 1.5 to 1.8 Btu·in./h·ft2·°F (0.22 to 0.26 W/(m·K)). Such values are considerably lower than those in Eq. (3.3a) or Eq. (3.3b) for typical lightweight aggregate concrete (void-free) (Valore 1980) because the air spaces found in the

Table 3.2b—Thermal conductivity of oven-dry lightweight concrete, mortar, and brick (SI units)*

Thermal conductivity kc, W/(m·K)Material, type of aggregate in concrete or data source

Oven-dry density, kg/m3

240 320 400 480 640 800 960 1120 1280 1440 1600 1760 1920 2080 2240 2400Equation (3.2) kc =

0.072e0.00125ρ 0.097 0.108 0.118 0.131 0.160 0.196 0.239 0.293 0.358 0.435 0.532 0.650 0.795 0.973 1.18 1.45

Neat cement paste and foam concrete 0.078 0.092 0.108 0.125 0.160 0.200 0.243 0.293 0.348 0.407 0.474 0.548 0.629 — — —

Autoclaved aerated (cellular) concrete 0.068 0.082 0.097 0.114 0.151 0.193 0.242 0.297 — — — — — — — —

Autoclaved microporous silica 0.059 0.073 0.088 0.104 0.138 0.180 0.228 0.281 0.343 — — — — — — —

Expanded polystyrene beads 0.072 0.089 0.107 0.127 0.170 0.220 0.280 — — — — — — — — —Expanded perlite 0.066 0.082 0.099 0.119 0.163 0.213 0.274 — — — — — — — — —

Exfoliated vermiculite 0.076 0.091 0.107 0.124 0.159 0.199 0.243 — — — — — — — — —Natural pumice — — — 0.107 0.147 0.195 0.249 0.316 0.391 0.479 0.581 — — — — —

Sintered fl y ash and coal cinders — — — — — — 0.169 0.304 0.369 0.441 0.524 0.617 — — — —

Volcanic slag and scoria — — — — — — 0.241 0.297 0.361 0.431 0.513 — — — — —Expanded slag — — — — — — 0.218 0.265 0.319 0.379 0.447 0.522 0.604 — — —

Expanded and sintered clay,shale, and slate — — — 0.125 0.167 0.214 0.271 0.321 0.408 0.490 0.584 0.689 — — — —

Sanded expanded clay, shale, and slate — — — — — 0.245 0.319 0.405 0.506 0.623 0.758 0.915 1.10 — — —

No-fi nes pumice, and expanded and

sintered clay, shale, and slate— — — 0.140 0.183 0.231 0.286 0.346 0.415 0.448 — — — — — —

Limestone — — — — — — — 0.371 0.461 0.568 0.691 0.831 0.992 1.18 1.39 1.63Cement-sand mortar and

foam concrete — — — — — — 0.339 0.429 0.536 0.660 0.804 0.970 1.16 — — —

Fired clay bricks — — — — — — — 0.316 0.378 0.446 0.523 0.609 0.702 0.804 0.921 1.05*Obtained from density/thermal conductivity linear equations.



0.568 0.691

0.660 0.804

) ranging from 0.47 to 0.95. Experimental

0.446 0.523

by 6 percent for

values averaged approximately 5 percent lower than calcu-lated values for pastes with and 16 percent lower for paste with 0.35

— 0.140 0.346 0.415 0.448

—

—

may be used to estimate

Obtained from density/thermal conductivity linear equations.

may be used to estimate k values

— — —

— —Obtained from density/thermal conductivity linear equations.

rial ratios (

— 0.339

— 0.316

rial ratios (

0.429 0.536

0.316 0.378

0.371 0.461



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Table 3.3—Thermal conductivity moisture correction factors*

Material or type of aggregate in concrete

Type of exposure

Relative humidity mean, %

Moisture content, percent by weight

Thermal conductivity moisture correction factor, percent increase

in thermal conductivity per 1 percent moisture content

Practical thermal conductivity multiplier

Neat cement paste and foam concrete; expanded polystyrene bead concrete

Pr† 80 8.0 3.0 1.25

Autoclaved aerated (cellular) concrete Pr 80 4.5 4.5 1.20

Expanded perlite and exfoliated vermiculite

Pr 80 6.5 4.5 1.30

Natural pumice PrUh‡

8080

5.57.0

4.254.25

1.221.30

Sintered fly ash, scoria, and coal cinders

PrUh

6080

3.755.0

6.06.0

1.221.30

Expanded slag PrUh

8080

3.55.5

5.55.5

1.201.30

Expanded and sintered clay, shale, slate (no natural sand); sanded

expanded slag

PrUh

8080

3.55.5

4.04.0

1.141.22

Sanded expanded and sintered clay, shale, and slate

PrUh

6080

3.05.0

5.05.0

1.151.25

Limestone PrUh

6080

2.03.0

7.07.0

1.151.22

Sand gravel, < 50 percent quartz or quartzite

PrUh

6080

2.03.0

7.07.0

1.151.22

Sand gravel, > 50 percent quartz or quartzite

PrUh

6080

2.03.0

9.09.0

1.181.27

Cement mortar, sanded Pr 60 2.0 9.0 1.20

Foam concrete Uh 80 3.0 9.0 1.30

Clay bricks PrUh

6080

0.52.0

30.020.0

1.151.40

*For converting thermal conductivity of oven-dry concretes and clay bricks to practical design values.†Pr = protected exposure: exterior wall stuccoed or coated with cement base, texture, or latex paint; interior wythe or cavity wall or of composite wall with full collar joint.‡Uh = unprotected: exterior wall surface uncoated, or treated with water repellent or thin, clear polymeric sealer only.

Note: Reproduced by permission from Valore (1988).

Table 3.4a—Thermal conductivity of some natural minerals (in.-lb units)

MineralThermal conductivity kc, Btu· in./

(h·ft2·°F)

Quartz (single crystal)* 87, 47

Quartz 40

Quartzite 22 to 37

Hornblende-quartz-gneiss 20

Quartz-monzonite 18

Sandstone 9 to 16

Granite 13 to 28

Marble 14 to 21

Limestone 6 to 22

Chalk 6

Diorite (dolerite) 15.6

Basalt (trap rock) 9.6 to 15

Slate 13.6*Thermal conductivity of single crystal quartz depends on the axis on which it is measured.

Table 3.4b—Thermal conductivity of some natural minerals (SI units)

MineralThermal conductivity kc, W/

(m·K)

Quartz (single crystal)* 12.5, 6.8

Quartz 5.8

Quartzite 3.2 to 5.3

Hornblende-quartz-gneiss 2.9

Quartz-monzonite 2.6

Sandstone 1.3 to 2.3

Granite 1.9 to 4.0

Marble 2.0 to 3.0

Limestone 0.8 to 3.2

Chalk 0.8

Diorite (dolerite) 2.2

Basalt (trap rock) 1.4 to 2.2

Slate 2.0*Thermal conductivity of single crystal quartz depends on the axis on which it is measured.





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zero-slump CMU lightweight concrete provide additional heat flow resistance, thus lowering the conductivity.

3.6—Thermal conductivity of two-phase systemsThe cubic model (Valore 1980) described in 3.7 shows

that the thermal conductivity of a discrete two-phase system, such as concrete, can also be calculated by knowing the volume fractions and the thermal conductivity values of the cement pastes and aggregates (Fig. 3.6). For lightweight-aggregate concretes, Eq. (3.2) yields kc values similar to those calculated by using the cubic-model equation (Eq. (3.7)). Equation (3.2) is not always accurate over a wide range of concrete densities (Valore 1980), particularly above 100 lb/ft3 (1600 kg/m3), because aggregate mineralogical characteristics cause a wide range of aggregate thermal conductivities. The cubic-model equation is appropriate for calculating thermal conductivities of concretes having densi-ties above 100 lb/ft3 (1600 kg/m3). The cubic-model equa-tion demonstrates how the factors that influence concrete thermal conductivity kc impose a ceiling limit on kc, even for concretes containing hypothetical aggregates with infi-nitely high thermal conductivities. The insulating effect of the cement paste matrix on kc is determined by the quantity

and quality of the paste volume fraction and its density. The cubic model also explains how normalweight aggregates produce disproportionately high conductivity values when added to lightweight-aggregate concrete.

At the same concrete density, a coarse-lightweight-aggregate grading provides concrete with a higher thermal-conductivity value than a fine-lightweight-aggregate-grading concrete due to the differences in aggregate (coarse fraction) and paste (fine grading) volume fractions.

3.7—Sample thermal conductivity calculations using cubic model

The cubic model (Valore and Green 1951; Valore 1958) can be used to calculate kc as a function of cement paste conductivity, aggregate conductivity, and aggregate volume. The cubic model (Fig. 3.6) is a unit volume cube of concrete consisting of a cube of aggregate of volume Va encased on all sides by a layer of cement paste of unit thickness (1 – Va

1/3)/2. The cubic model also accounts for the fact that concrete is a thermally and physically heterogeneous material and may contain highly conductive aggregates that serve as thermal bridges or shunts. Thermal bridges are highly conduc-tive materials, surrounded by materials with relatively low conductivity, that greatly increase the composite system’s conductivity. In the case of concrete, highly conductive aggregates are the thermal bridges surrounded by the lower conductive cement paste, fine aggregate matrix, or both. To use the cubic model (Eq. (3.7)), thermal conductivity values for cement paste kp, aggregate ka, and aggregate volume Va are required for estimating the thermal conductivity of concrete. Aggregate volume is obtained from measurements made for compacted aggregate using ASTM C29/C29M.

Fig. 3.4––Thermal conductivity kp for air-dry-hardened portland cement pastes.

Fig. 3.6—Cubic model for calculating thermal conduc-tivity kc of concrete as a function of conductivity kp and ka of cement paste and aggregate, and volume fraction Va of aggregate.





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k kV

V V Vk Vk

V

c pa

a aa

a a

pa

=

− +

+ −

2 3

2 3

2 32 31

/

/

//

(3.7)

When fine and coarse aggregate ka values differ, kc is calculated for the paste/fine aggregate mortar first and the

calculation is then repeated for the paste/coarse aggregate combination using the appropriate Va value in each step. For concretes weighing 120 lb/ft3 (1920 kg/m3) or less, thermal conductivities determined using Eq. (3.7) show good agree-ment with the thermal conductivity determined using the simpler conductivity/density relationship of Eq. (3.2). For normalweight concretes with densities greater than 120 lb/ft3 (1920 kg/m3), results obtained using Eq. (3.7) yield more accurate kc values than Eq. (3.2) when compared to test data shown in Tables 3.2a and 3.2b.

3.8—Practical thermal conductivityPractical thermal conductivity design values for normal-

weight and lightweight concrete, solid clay brick, cement mortar, and gypsum materials are suggested in Tables 3.8a and 3.8b (Valore 1988).

Table 3.8a—Compiled historical thermal conductivity design values (in.-lb units)*

Practical thermal conductivity, Btu·in./(h·ft2·°F)

Group

Material or type of aggregate of

concreteExposure

type†

Oven-dry density, lb/ft3

15 20 25 30 40 50 60 70 80 90 100 110 120 130 140 150Matrix

insulatedNeat cement paste and foam concrete

Pr 0.7 0.8 0.9 1.1 1.4 0.7 2.1 2.5 3.0 3.5 4.1 4.7 5.4 — — —

Insulated structural

Autoclaved aerated (cellular)

Pr 0.6 0.7 0.8 1.0 1.3 1.6 2.0 2.5 — — — — — — — —

Insulated

Expanded polysty-rene beads, perlite,

vermiculite, expand, glass

Pr 0.65 0.8 0.95 1.1 1.5 1.9 2.4 — — — — — — — — —

Concrete masonry structural

Unsanded, expanded, and sintered clay,

shale, slate, fly ash; cinders, scoria,

pumice, sanded-expanded slag

PrUn

——

——

——

——

1.31.4

1.71.8

212.3

2.62.8

3.253.5

4.04.25

4.655.0

5.55.9

6.46.8

——

——

——

Concrete masonry, structural

Unsanded expanded slag

PrUn

——

——

——

——

——

——

1.82.0

2.22.4

2.72.9

3.23.4

3.74.0

4.34.7

——

——

——

——


Sanded expanded and sintered clay,

shale, slate, fly ash; sanded pumice, scoria, cinders

PrUn

——

——

——

——

——

1.92.1

2.52.7

3.23.5

4.14.4

5.15.5

6.26.8

7.68.2

9.19.9

——

——

——

Concrete masonry,structural

LimestonePrUn

——

——

——

——

——

——

——

——

——

——

5.55.85

6.67.0

7.98.3

9.410.0

11.1511.7

13.813.75


Sand gravel, <50 percent quartz or

quartzite

PrUn

——

——

——

——

——

——

——

——

——

——

——

——

——

10.010.7

13814.6

18.519.6


Sand gravel, >50 percent quartz or

quartzite

PrUn

——

——

——

——

——

——

——

——

——

——

——

——

——

11.011.8

15.316.5

20.522.0

Concrete masonry, insulated structural

Cement-sand mortar; sanded foam concrete

solid clay bricks

PrUnPrUn

————

————

————

————

————

————

2.83.1——

3.63.92.53.1

4.54.83.03.7

5.56.03.64.3

6.77.34.25.1

8.18.74.95.9

9.710.55.66.8

11.512.46.47.8

13.514.77.49.0

——8.410.2

*For normalweight and lightweight concretes, solid clay bricks, and cement mortars.†Pr = protected exposure; mean relative humidity in wall up to 60 percent. Exterior wall surface coated with stucco, cement-based paint, or continuous coating of latex paint; or inner wythe of composite wall with a full collar joint, or inner wythe of cavity wall. Un = unprotected exposure; mean relative humidity in wall up to 80 percent. Exterior wall surface uncoated or treated with a water repellent or clear sealer only. Pr Un = densities above 100 lb/ft3 do not apply to pumice or expanded clay or shale concretes.






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CHAPTER 4—CALCULATION METHODS FOR STEADY-STATE THERMAL RESISTANCE OF WALL

SYSTEMS

4.1—IntroductionThermal resistance R is the most widely used and recog-

nized thermal property. Building codes generally prescribe requirements for minimum R-values or maximum thermal transmittance, U-value, for elements of a building enve-lope. There are multiple methods for calculating the thermal

properties of building assemblies. The methods include the series method, parallel path method, isothermal planes method (also referred to as the series parallel method), and zone method. Each of these methods may be used to deter-mine compliance with the building code for specific building assembly constructions. Actual test data or data determined using more sophisticated modeling techniques, such as two- or three-dimensional finite element or finite difference methods (which are not addressed in this guide), are gener-ally accepted by the building code official.

Table 3.8b—Compiled historical thermal conductivity design values (SI units)*Practical thermal conductivity, W/(m·K)

Group

Material or type of aggregate of

concrete

Expo-suretype†

Oven-dry density, kg/m3

240 320 400 480 640 800 960 1120 1280 1440 1600 1760 1920 2080 2240 2400

Matrixinsulated

Neat cement paste and foam

concrete

Pr 0.101 0.115 0.130 0.159 0.202 0.101 0.303 0.361 0.433 0.505 0.591 0.678 0.779 — — —

Insulated structural

Autoclaved aerated

(cellular)

Pr 0.087 0.101 0.115 0.144 0.187 0.231 0.288 0.361 — — — — — — — —

Insulated

Expanded polystyrene

beads, perlite, vermiculite,

expand, glass

Pr 0.094 0.115 0.137 0.159 0.216 0.274 0.346 — — — — — — — — —

Concrete masonry structural

Unsanded, expanded, and sintered clay,

shale, slate, fly ash; cinders,

scoria,pumice, sanded-expanded slag

PrUn

——

——

——

——

0.187 0.202

0.2450.260

0.303 0.332

0.375 0.404

0.469 0.505

0.577 0.613

0.671 0.721

0.793 0.851

0.923 0.981

——

——

——


Unsanded expanded slag

PrUn

——

——

——

——

——

——

0.260 0.288

0.317 0.346

0.389 0.418

0.461 0.490

0.534 0.577

0.620 0.678

——

——

——

——


Sanded expanded and sintered clay,

shale, slate, fly ash; sanded

pumice, scoria, cinders

PrUn

——

——

——

——

——

0.274 0.303

0.361 0.389

0.461 0.505

0.5910.634

0.735 0.793

0.894 0.981

1.101.18

1.311.38

——

——

——

Concrete masonry,structural

LimestonePrUn

——

——

——

——

——

——

——

——

——

——

0.7930.844

0.9521.01

1.141.20

1.361.44

1.611.69

1.991.98


Sand gravel, <50 percent

quartz or quartzite

PrUn

——

——

——

——

——

——

——

——

——

——

——

——

——

1.441.54

1.991.67

2.672.82


Sand gravel, >50 percent

quartz or quartzite

PrUn

——

——

——

——

——

——

——

——

——

——

——

——

——

1.591.70

2.212.38

2.963.17

Concrete masonry, insulated structural

Cement-sand mortar; sanded foam concrete

solid clay bricks

PrUnPrUn

————

————

————

————

————

————

0.4040.447

——

0.5190.5620.3610.447

0.6490.6920.4330.534

0.7930.8650.5190.620

0.9961.050.6050.735

1.171.250.7060.851

1.401.510.7060.851

1.661.790.9231.12

1.952.121.071.30

——

*For normalweight and lightweight concretes, solid clay bricks, and cement mortars.†Pr = protected exposure; mean relative humidity in wall up to 60 percent. Exterior wall surface coated with stucco, cement-based paint, or continuous coating of latex paint; or inner wythe of composite wall with a full collar joint, or inner wythe of cavity wall. Un = unprotected exposure; mean relative humidity in wall up to 80 percent. Exterior wall surface uncoated or treated with a water repellent or clear sealer only. Pr Un = densities above 100 lb/ft3 do not apply to pumice or expanded clay or shale concretes.






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The series method (ASHRAE 2009) is acceptable for calculating the thermal conductance of assemblies containing only thermally homogeneous layers. The parallel path method (ASHRAE 2009) is appropriate for use in calculating the thermal conductance of assemblies constructed with layers containing multiple thermal paths of heterogeneous materials where the thermal conductivities of each material within any layer are similar. The parallel path method was historically used for calculating the thermal conductance of uninsulated concrete masonry units because the thermal conductance of the mortar and face shells and air spaces in cores and webs were determined to have suffi-ciently similar thermal conductivities. Placing materials with significantly different thermal conductances within a layer, however, results in energy flowing through the path of least resistance. This wicking effect alters the overall thermal conductance of many insulated concrete masonry units. The isothermal planes method (ASHRAE 2009) demonstrates adequate agreement with the test results to be acceptable for determining code compliance. Where large cross-sectional areas of highly conductive materials, such as steel studs, are used within an assembly, thermal conductances should be determined using the zone method described in ASHRAE (2009). Generally, the effects of small, infrequent thermal anomalies (also referred to as thermal bridges) such as those that result from crossties of horizontal joint reinforcement can be ignored. For larger or more frequent thermal anoma-lies, however, the isothermal planes method or zone method should be employed.

4.2—Thermal resistance of concrete masonry wallsThermal resistance of concrete masonry walls is affected

by many variables, including unit shape and size, concrete density, insulation types, aggregate type(s), aggregate grada-tion, aggregate mineralogy, cementitious binder, and mois-ture content. It is not feasible to test all of the possible varia-tions. More than 100 CMU walls, however, have been tested (refer to Tables A.1a, A.1b, A.2a, and A.2.b) (Valore 1980). These tests provide a basis for comparison of various calcu-lation methods. Two calculation methods have traditionally been widely used: the parallel-path method and the series-parallel method (also known as isothermal planes). Note that the parallel path method was generally accepted for code compliance up to the mid-1980s. After this time, the series-parallel method was being introduced into many building codes as the required method, as it better estimates the thermal bridging through the webs of conventional concrete masonry units containing insulation in the cores. With the publication of the first edition of the International Energy Conservation Code (ICC 2000), the series-parallel method became the recognized method in the model building codes and remains the current recommended method (ICC 2012; ANSI/ASHRAE/IES 90.1; ANSI/ASHRAE/IES 90.2) in the model building code and referenced standards. The parallel-path and series-parallel methods are both described in 4.3.

Calculated R-values (based on the series-parallel method) for various single-wythe concrete masonry wall assemblies are listed in Tables 4.2a and 4.2b. Note that the walls in

Tables 4.2a and 4.2b are single wythe with no interior or exterior insulation and no finishes. R-values of any interior or exterior insulation or finish systems are simply added to the R-value of the concrete masonry wall from Tables 4.2a and 4.2b.

Tables 4.2a and 4.2b include U-values and R-values of both ungrouted and fully grouted or 100 percent solid unit walls. For partially grouted walls, the values must be modi-fied to account for the relative amounts of ungrouted and grouted cores. The overall U-value of the partially grouted masonry wall is calculated from the area-weighted average of the U-value of the grouted area and the U-value of the ungrouted area, as follows

U = (agr x Ugr) + (aungr x Uungr) (4.2)

Proportionate areas for typical grouted and ungrouted nominal 8 in. (203 mm) concrete masonry units are provided in Tables 4.2c and 4.2d. Comprehensive tables of calculated R-values have been compiled by the National Concrete Masonry Association (2010) and include both single- and multi-wythe walls with various insulation types and amounts, wall finishes, and grout schedules.

4.3—Methods for calculating thermal resistance of concrete masonry units

The parallel-path method was considered acceptable practice until insulated CMUs appeared in the market-place. The parallel-path method assumes that heat flows in straight parallel lines through a CMU. If a hollow CMU has 20 percent web area and 80 percent core area, this method assumes that 20 percent of the heat flow occurs through the web and 80 percent occurs through the core (Fig. 4.3a). This method is reasonably accurate for uninsulated hollow CMUs.

The series-parallel (also known as isothermal planes) method is the current practice and provides good agreement with test data for both uninsulated and insulated CMUs. As with fluid flow and electrical currents, the series-parallel method considers that heat flow follows the path of least resistance. It accounts for lateral heat flows in CMU face shells and heat bypassing areas of relatively high thermal resistance, such as air spaces or insulation in the hollow cores. Therefore, CMU cross webs are a thermal bridge. As shown in Fig. 4.3b, heat flow is mostly concentrated in webs.

The basic equation for the series-parallel method is as follows

R R RaR

aR

aR

aR

T o inp

np

np

np

np

np

np

np

= + +

+

+…+

+

1 1

(4.3)

Using this method, the masonry unit is divided into ther-mally heterogeneous layers that occur at all changes in unit geometry and at all interfaces between adjacent materials. For example, a conventional (that is, three full-height webs, two cores), hollow, uninsulated CMU has three thermal layers:





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1. The interior face shell and mortar joint2. The hollow-core air spaces and cross webs3. The exterior face shell and mortar jointA conventional hollow CMU with an insulation insert

placed over reduced cross webs in the middle of the CMU has five thermal layers, as shown in Fig. 4.3b:

1. The interior face shell and mortar joint2. The full-height concrete webs and hollow-core air space3. The reduced-height concrete webs combined with the

insulating insert and air space above/below (as applicable) the insert

4. The full-height concrete webs and hollow-core air space

Table 4.2a—Calculated R-values, (h·ft2·°F)/Btu, of single-wythe concrete masonry walls (in.-lb units)*

Nominal wythe

thickness,in.

Densityof

concrete,lb/ft3

Cores empty

Cores filled with†100% solid units and hollow units grouted

solidLoose-fill insulation Polyurethane

foamed-in-placePerlite VermiculiteU R U R U R U R U R

4‡

85 0.475 2.1 0.251 4.0 0.274 3.6 0.220 4.5 0.577 1.795 0.501 2.0 0.284 3.5 0.306 3.3 0.255 3.9 0.635 1.6

105 0.530 1.9 0.323 3.1 0.342 2.9 0.296 3.4 0.694 1.4115 0.560 1.8 0.366 2.7 0.384 2.6 0.342 2.9 0.752 1.3125 0.593 1.7 0.416 2.4 0.432 2.3 0.394 2.5 0.808 1.2135 0.628 1.6 0.470 2.1 0.484 2.1 0.451 2.2 0.860 1.2

6

85 0.433 2.3 0.189 5.3 0.204 4.9 0.170 5.9 0.605 1.795 0.459 2.2 0.219 4.6 0.233 4.3 0.200 5.0 0.640 1.6

105 0.486 2.1 0.253 4.0 0.266 3.8 0.236 4.2 0.675 1.5115 0.515 1.9 0.293 3.4 0.305 3.3 0.277 3.6 0.707 1.4125 0.546 1.8 0.339 2.9 0.350 2.9 0.325 3.1 0.738 1.4135 0.580 1.7 0.391 2.6 0.400 2.5 0.378 2.6 0.767 1.3

8

85 0.402 2.5 0.142 7.0 0.154 6.5 0.126 7.9 0.525 1.995 0.427 2.3 0.165 6.1 0.177 5.6 0.150 6.7 0.559 1.8

105 0.452 2.2 0.193 5.2 0.204 4.9 0.179 5.6 0.592 1.7115 0.479 2.1 0.226 4.4 0.236 4.2 0.213 4.7 0.623 1.6125 0.507 2.0 0.264 3.8 0.274 3.6 0.252 4.0 0.654 1.5135 0.537 1.9 0.309 3.2 0.317 3.2 0.298 3.4 0.684 1.5

10

85 0.394 2.5 0.116 8.6 0.125 8.0 0.104 9.6 0.478 2.195 0.417 2.4 0.136 7.4 0.145 6.9 0.124 8.1 0.507 2.0

105 0.441 2.3 0.160 6.3 0.169 5.9 0.149 6.7 0.535 1.9115 0.465 2.2 0.189 5.3 0.197 5.1 0.179 5.6 0.563 1.8125 0.491 2.0 0.224 4.5 0.231 4.3 0.214 4.7 0.591 1.7135 0.518 1.9 0.264 3.8 0.271 3.7 0.225 4.4 0.618 1.6

12

85 0.390 2.6 0.094 10.6 0.102 9.8 0.084 11.9 0.441 2.395 0.411 2.4 0.111 9.0 0.118 8.5 0.101 9.9 0.466 2.1105 0.433 2.3 0.131 7.6 0.138 7.2 0.122 8.2 0.490 2.0115 0.455 2.2 0.155 6.5 0.162 6.2 0.146 6.8 0.515 1.9125 0.478 2.1 0.185 5.4 0.191 5.2 0.176 5.7 0.539 1.9135 0.503 2.0 0.219 4.6 0.226 4.4 0.212 4.7 0.564 1.8

14

85 0.387 2.6 0.079 12.7 0.086 11.6 0.070 14.3 0.409 2.495 0.408 2.5 0.093 10.8 0.100 10.0 0.085 11.8 0.431 2.3105 0.428 2.3 0.111 9.0 0.117 8.5 0.103 9.7 0.452 2.2115 0.449 2.2 0.132 7.6 0.138 7.2 0.124 8.1 0.474 2.1125 0.470 2.1 0.157 6.4 0.163 6.1 0.150 6.7 0.496 2.0135 0.492 2.0 0.188 5.3 0.193 5.2 0.181 5.5 0.518 1.9

16

85 0.385 2.6 0.068 14.7 0.074 13.5 0.061 16.4 0.381 2.695 0.405 2.5 0.081 12.3 0.086 11.6 0.073 13.7 0.400 2.5105 0.425 2.4 0.096 10.4 0.101 9.9 0.089 11.2 0.420 2.4115 0.445 2.2 0.114 8.8 0.120 8.3 0.108 9.3 0.439 2.3125 0.465 2.2 0.137 7.3 0.142 7.0 0.130 7.7 0.459 2.2135 0.485 2.1 0.164 6.1 0.169 5.9 0.158 6.3 0.480 2.1

*Mortar joints are 3/8 in. thick, with face shell mortar bedding (except 4 in. solid units, which are assumed to have full mortar bedding). Unit dimensions are based on ASTM C90. Surface air films are included.†Values apply when all masonry cores are filled completely. Grout density is 140 lb/ft2. Lightweight grouts, which will provide higher R-values, may also be available in some areas.‡Because of the small core size and resulting difficulty consolidating grout, 4 in. units are rarely grouted. Note that filling the cores of these units may also be difficult. Values are for 100 percent solid 4 in. units. Full mortar bedding is assumed for 4 in. units.





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5. The exterior face shell and mortar jointThe series-parallel method also dictates that thermal

layers be further divided into heat-flow paths corresponding to the materials in each layer. For example, in the reduced-cross-web insulated CMU (Fig. 4.3b), layer one has two heat-flow paths: the concrete in the face shell and the mortar

in the mortar joint. Layer three has three heat-flow paths: the reduced cross web concrete, the insert insulation, and the air space. As is the case in most commercially available insu-lated CMUs, the insulating insert does not completely wrap the unit’s webs (that is, it does not cover the mortar joint area and it does not have a 8 x 16 in. [200 x 400 mm] profile to

Table 4.2b—Calculated R-values, (m2·K)/W, of single-wythe concrete masonry walls (SI units)*

Nominal wythe

thickness, mm

Density ofconcrete,

kg/m3

Cores empty

Cores filled with†100% solid units and hollow units grouted

solidLoose-fill insulation Polyurethane

foamed-in-placePerlite VermiculiteU R U R U R U R U R

102‡

1360 2.70 0.371 1.43 0.701 1.56 0.643 1.25 0.800 3.28 0.3051520 2.85 0.351 1.61 0.620 1.74 0.575 1.49 0.690 3.61 0.2771680 3.01 0.332 1.84 0.545 1.94 0.515 1.68 0.595 3.94 0.2541840 3.18 0.314 2.08 0.481 2.18 0.458 1.94 0.515 4.27 0.2342000 3.37 0.297 2.36 0.423 2.45 0.408 2.24 0.447 4.59 0.2182160 3.57 0.280 2.67 0.375 2.75 0.364 2.56 0.390 4.89 0.205

152

1360 2.46 0.407 1.07 0.932 1.16 0.863 0.966 1.04 3.44 0.2911520 2.61 0.384 1.24 0.804 1.32 0.756 1.14 0.880 3.64 0.2751680 2.76 0.362 1.44 0.696 1.51 0.662 1.34 0.746 3.83 0.2611840 2.93 0.342 1.66 0.601 1.73 0.577 1.57 0.636 4.02 0.2492000 3.10 0.322 1.93 0.519 1.99 0.503 1.85 0.542 4.19 0.2392160 3.29 0.304 2.22 0.450 2.27 0.440 2.15 0.466 4.36 0.230

203

1360 2.28 0.438 0.807 1.24 0.875 1.14 0.716 1.40 2.98 0.3351520 2.43 0.412 0.937 1.06 1.01 0.995 0.852 1.17 3.18 0.3151680 2.57 0.390 1.10 0.912 1.16 0.863 1.02 0.984 3.36 0.2971840 2.72 0.368 1.28 0.779 1.34 0.746 1.21 0.827 3.54 0.2832000 2.88 0.347 1.50 0.667 1.56 0.643 1.43 0.699 3.72 0.2692160 3.05 0.328 1.76 0.570 1.80 0.555 1.69 0.591 3.89 0.257

254

1360 2.24 0.447 0.659 1.52 0.710 1.41 0.591 1.69 2.72 0.3681520 2.37 0.422 0.772 1.30 0.824 1.21 0.704 1.42 2.88 0.3471680 2.51 0.399 0.909 1.10 0.960 1.04 0.846 1.18 3.04 0.3291840 2.64 0.379 1.07 0.932 1.12 0.894 1.02 0.984 3.20 0.3132000 2.79 0.359 1.27 0.786 1.31 0.762 1.22 0.823 3.36 0.2982160 2.94 0.340 1.50 0.667 1.54 0.650 1.28 0.782 3.51 0.285

305

1360 2.22 0.451 0.534 1.87 0.579 1.73 0.477 2.10 2.51 0.3991520 2.33 0.428 0.630 1.59 0.670 1.49 0.574 1.74 2.65 0.3781680 2.46 0.407 0.744 1.34 0.784 1.28 0.693 1.44 2.78 0.3591840 2.58 0.387 0.880 1.14 0.920 1.09 0.829 1.21 2.93 0.3422000 2.72 0.368 1.05 0.952 1.09 0.922 1.00 1.00 3.06 0.3272160 2.86 0.350 1.24 0.804 1.28 0.779 1.20 0.830 3.20 0.312

356

1360 2.20 0.455 0.449 2.23 0.488 2.05 0.398 2.52 2.32 0.4301520 2.32 0.432 0.528 1.89 0.568 1.76 0.483 2.07 2.45 0.4081680 2.43 0.411 0.630 1.59 0.665 1.51 0.585 1.71 2.57 0.3901840 2.55 0.392 0.750 1.33 0.784 1.28 0.704 1.42 2.69 0.3712000 2.67 0.375 0.892 1.12 0.926 1.08 0.852 1.17 2.82 0.3552160 2.80 0.358 1.07 0.936 1.10 0.912 1.03 0.973 2.94 0.340

406

1360 2.19 0.457 0.386 2.60 0.420 2.38 0.346 2.89 2.16 0.4621520 2.30 0.435 0.460 2.17 0.488 2.05 0.415 2.41 2.27 0.4401680 2.41 0.414 0.545 1.83 0.574 1.74 0.506 1.98 2.39 0.4191840 2.53 0.396 0.648 1.54 0.682 1.47 0.613 1.63 2.49 0.4012000 2.64 0.379 0.778 1.29 0.807 1.24 0.738 1.35 2.61 0.3842160 2.76 0.363 0.932 1.07 0.960 1.04 0.897 1.11 2.73 0.367

*Mortar joints are 9.5 mm thick, with face shell mortar bedding (except 102 mm solid units, which are assumed to have full mortar bedding). Unit dimensions are based on ASTM C90. Surface air films are included.†Values apply when all masonry cores are filled completely. Grout density is 2243 kg/m3. Lightweight grouts, which will provide higher R-values, may also be available in some areas.‡Because of the small core size and resulting difficulty consolidating grout, 102 mm units are rarely grouted. Note that filling the cores of these units may also be difficult. Values are for 100 percent solid 102 mm units. Full mortar bedding is assumed for 102 mm units.





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fully cover a typical CMU’s area). Hence, Layer 3 has three heat-flow paths. If the insulation insert does, in fact, have an 8 x 16 in. (200 x 400 mm) profile, then the layer has only two heat flow paths: the reduced cross web and the insulation insert. Tables 4.3a and 4.3b list standard CMU dimensions.

4.4—Thermal resistance of other concrete wall systems

The series-parallel method can also be used to calculate the thermal resistance of other concrete wall systems, such as tilt-up walls, precast walls, insulated sandwich panels, and cast-in-place walls. Wall-shear connectors and solid-concrete perimeters in sandwich panels can have relatively high thermal conductivities and will act as thermal bridges in the same manner as webs do in CMUs. When these wall types do not contain thermal bridges, the series-parallel equation can be simplified to a series equation; that is, adding the resistances of each layer because each layer has only one path.

4.4.1 Sample calculations—The following three examples were developed by McCall (1985). Although Eq. (4.4.1.2)

and (4.4.1.3) look different from Eq. (4.3), the basic prin-ciples of series-parallel heat flow are represented.

4.4.1.1 Case I: No steel ties—A sandwich panel is illus-trated in Fig. 4.4.1.1 with a 2 in. (50.8 mm) concrete inner wythe, 2 in. (50.8 mm) extruded polystyrene insulation, and a 2 in. (50.8 mm) concrete outer wythe with no steel ties penetrating the insulation. The concrete has a density of 150 lb/ft3 (2400 kg/m3). To calculate the U-value of this panel, add the individual thermal resistances of the inside surface air film, the inner wythe of concrete, the insulation, the outer wythe of concrete, and the outside surface air film and then take the reciprocal of this sum. The U-value of this panel is 0.09 Btu/(h·ft2·°F) (0.51 W/(m2·K)). The results are illus-trated in Tables 4.4.1.1a and 4.4.1.1b.

4.4.1.2 Case II: Steel ties—In comparison, consider a sandwich panel that has the same characteristics as the previous example except that it has 3/8 in. (9.5 mm) diam-eter bars penetrating the insulation and 1 in. (25.4 mm) into each wythe of concrete, as illustrated in Fig. 4.4.1.2.

To calculate the thermal resistance of the insulating layer, use the formula

Rt = RinRs/(aiRs + asRin) (4.4.1.2)

The thermal resistance of the insulating layer with No. 3 bar shear ties as shown in Table 4.4.1.2a is 6.26 (h·ft2·°F)/Btu (1.10 (m2·K)/W). When compared to the previous example, it shows that if steel occupies 0.08 percent of the area of the insulation layer, the thermal resistance of the insulation layers is reduced from 10.00 h·ft2·°F/Btu (1.79 (m2·K)/W) to 6.26 h·ft2·°F/Btu (1.10 (m2·K)/W)—a 38 percent reduction.

The U-value of the panel is calculated as the reciprocal of the sum of the thermal resistances of individual layers, as illustrated in Tables 4.4.1.2a and 4.4.1.2b.

Table 4.2c—Ungrouted area: grouted area for partially grouted nominal 8 in. concrete masonry walls (in.-lb units)*

Vertical grout spacing, in.No vertical grout 48 40 32 24 16

Horizontal grout spacing, in.

No horizontal grout 100:0 83:17 80:20 75:25 67:33 50:5048 83:17 69:31 67:33 63:37 56:44 42:5840 80:20 67:33 64:36 60:40 53:47 40:6032 75:25 63:37 60:40 56:44 50:50 37:6324 67:33 56:44 53:47 50:50 44:56 33:6716 50:50 42:58 40:60 37:63 33:67 25:75

*Expressed as a percentage. Example: A wall grouted at 32 in. on center vertically, with no horizontal grout, has approximately 75 percent of the wall ungrouted and 25 percent grouted.

Table 4.2d—Ungrouted area: grouted area for partially grouted 203 mm concrete masonry walls (SI units)*

Vertical grout spacing, mmNo vertical grout 1219 1016 813 610 406

Horizontal grout spacing, mm

No horizontal grout 100:0 83:17 80:20 75:25 67:33 50:501219 83:17 69:31 67:33 63:37 56:44 42:581016 80:20 67:33 64:36 60:40 53:47 40:60813 75:25 63:37 60:40 56:44 50:50 37:63610 67:33 56:44 53:47 50:50 44:56 33:67406 50:50 42:58 40:60 37:63 33:67 25:75

*Expressed as a percentage. Example: A wall grouted at 813 mm on center vertically, with no horizontal grout, has approximately 75 percent of the wall ungrouted and 25 percent grouted.

Fig. 4.3a––Parallel and series parallel heat flow schematics.





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Fig. 4.3b—Five layers of an insulated hollow CMU.





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4.4.1.3 Case III:Steel ties plus solid concrete—To illus-trate the effect a 6 in. (150 mm) solid concrete around the perimeter of the panel (Fig. 4.4.1.3) would have on the U-value, use the parallel-resistance formula for three mate-rials to calculate the thermal resistance.

Rt = RsRcRin/(asRinRc + aiRsRc + acRsRin) (4.4.1.3)

where the total R-value for the insulating layer is 2.31 (h·ft2·°F)/Btu (0.407 (m2·K)/W), which is a 77 percent reduction from the 10.00 (h·ft2·°F)/Btu (1.79 (m2·K)/W)

R-value of the insulation without any penetrations.

Table 4.3b—Dimensions of plain-end two-core concrete masonry units for calculating U-values (SI units)Thickness, mm Actual length,

mmCombined thickness of two face shells,* mm

Combined thickness of three webs,* mm

Fractional web face area, mm2†

Fractional core face area, mm2†

Average core thickness or web length, mmNominal Actual

Lb La 2fs w aw (w/A) ac (1 – aw) Lf or Lw = (Lb – 2fs)100 92 397 38 57 93 503 53150 143 397 51 76 124 503 92200 194 397 63 76 124 503 130250 244 397 63 85 139 490 181300 295 397 63 85 139 490 231

*Based on ASTM C90.†Assuming three full-height webs.

Fig. 4.4.1.1—Case I, no steel ties.

Table 4.4.1.1a—Thermal properties of sandwich panels with no shear ties (in.-lb units)

Panel components Thermal resistance, (°F·h·ft2)/BtuInside air film 0.68Inner wythe 0.17Insulation 10.00

Outer wythe 0.17Outer air film (15 mph wind) 0.17

Total thermal resistance 11.19U-value = 1/11.19 = 0.09 Btu/h·ft2·°F

Note: Reprinted from McCall (1985).

Table 4.4.1.1b—Thermal properties of sandwich panels with no shear ties (SI units)

Panel components Thermal resistance, (m2·K)/WInside air film 0.120Inner wythe 0.030Insulation 1.76

Outer wythe 0.030Outer air film (6.7 m/s wind) 0.030

Total thermal resistance 1.97U-value = 1/1.97 = 0.508 W/(m2·K)

Note: Reprinted from McCall (1985).

Table 4.3a—Dimensions of plain-end two-core concrete masonry units for calculating U-values (in.-lb units)

Thickness, in. Actual length, in.

Combined thickness of two face shells, in.

Combined thickness of three webs,* in.

Fractional web face area, in.2†

Fractional core face area, in.2†

Average core thickness or web length, in.Nominal Actual

Lb La 2fs w aw (w/A) ac (1 – aw) Lf or Lw = (Lb – 2fs)4 3.625 15.625 1.5 2.250 0.144 0.78 2.1256 5.625 15.625 2.0 3.000 0.192 0.78 3.6258 7.625 15.625 2.5 3.000 0.192 0.78 5.12510 9.625 15.625 2.5 3.375 0.216 0.76 7.12512 11.625 15.625 2.5 3.375 0.216 0.73 9.125

*Based on ASTM C90.†Assuming three full-height webs.

Fig. 4.4.1.2—Case II, steel ties.





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To calculate the U-value for this panel, add the individual thermal resistances and take the reciprocal, as illustrated in Tables 4.4.1.3a and 4.4.1.3b.

CHAPTER 5—THERMAL INERTIA

5.1—IntroductionThe term “thermal inertia” describes the absorption and

storage of significant amounts of heat in a building or in walls of a building. Concrete and masonry heat and cool slowly

and stay warm (or cool) longer than many other building materials. This thermal inertia effect delays and reduces heat transfer through a concrete or masonry wall, resulting in a reduction in total heat loss or gain through the building envelope. Heat transfer through concrete and masonry is reduced because of reversals of heat flow within the material due to changes in outdoor temperatures, and because some of the heat is stored in the element and later released back into the environment. Outdoor daily temperature cycles have less effect on the temperature inside a thermally massive building because massive materials reduce heat transfer and moderate the indoor temperature.

Concrete and masonry walls often perform better than indicated by R-values because R-values are determined under steady-state temperature conditions. Thus, a thermally massive building will generally use less energy than a frame building insulated by materials of the same R-value. Labora-tory tests or computer simulations can be used to quantify the energy savings. These methods have permitted building codes to allow lower R-values for mass walls than for frame walls while achieving the same thermal performance.

5.2—Factors affecting thermal inertia effectMany interrelated factors contribute to the actual energy

savings due to the thermal inertia of a building. These include the amount and placement of concrete or masonry materials, insulation, and windows; the building orientation; and the climate. The relative importance of each of these factors depends on the building use and design.

5.2.1 Thermal diffusivity—A high thermal diffusivity indi-cates that heat transfer through a material will be fast and the amount of storage will be small. Materials with a high thermal diffusivity respond quickly to changes in tempera-ture. Low thermal diffusivity means a slower rate of heat transfer and a larger amount of heat storage. Materials with low thermal diffusivity (such as concrete and masonry) respond slowly to an imposed temperature difference and are effective thermal inertia elements in a building.

5.2.2 Heat capacity—Heat capacity is another indicator of thermal inertia, one that is often used in energy codes. Concrete and masonry, because they absorb heat slowly, will generally have higher heat capacities than other mate-

Table 4.4.1.2a—Thermal properties of sandwich panel with No. 3 bar shear ties (in.-lb units)

Panel components Thermal resistance, (°F·h·ft2)/BtuInside air film 0.68Inner wythe 0.08

Insulation + 2 in. of concrete 6.26Outer wythe 0.08

Outside air film 0.17Total thermal resistance 7.27

U-value = 1/7.27 = 0.14 Btu/(h·ft2·°F)Note: Reprinted from McCall (1985).

Table 4.4.1.2b—Thermal properties of sandwich panel with No. 3 bar shear ties (SI units)

Panel components Thermal resistance, (m2·K)/WInside air film 0.120Inner wythe 0.014

Insulation + 50 mm of concrete 1.10Outer wythe 0.014


U-value = 1/1.28 = 0.781W/(m2·K)Note: Reprinted from McCall (1985).

Fig. 4.4.1.3—Case III, steel ties plus solid concrete.

Table 4.4.1.3a—Thermal properties of sandwich panel with No. 3 bars used as shear ties and a 6 in. solid concrete around the perimeter (in.-lb units)

Panel components Thermal resistance, (°F·h·ft2)/BtuInside air film 0.68Inner wythe 0.08

Insulation + 2 in. of concrete 2.31Outer wythe 0.08


U-value = 1/3.32 = 0.30 Btu/(h·ft2·°F)Note: Reprinted from McCall (1985).

Table 4.4.1.3b—Thermal properties of sandwich panel with No. 3 bars used as shear ties and a 152 mm solid concrete around the perimeter (SI units)

Panel components Thermal resistance, (m2·K)/WInside air film 0.120Inner wythe 0.014

Insulation + 50 mm of concrete 0.407Outer wythe 0.014


U-value = 1/0.585 = 1.71 W/(m2·K)Note: Reprinted from McCall (1985).





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rials. For example, a single-wythe concrete masonry wall weighing 34 lb/ft2 (166 kg/m2) with a specific heat of 0.21 Btu/(lb·°F) (880 J/(kg·K)) has a heat capacity of 7.14 Btu/(ft2·°F) (46,080 J/(m2·K)). The total wall heat capacity is simply the sum of the heat capacities of each wall compo-nent. Tables 5.2.2a and 5.2.2b list specific heat and heat capacity values for concrete masonry materials and for several masonry wall finishes. Tables 5.2.2c through 5.2.2f list heat capacity values for several masonry wall systems. When using inch-pound units, a reasonable approximation

for calculating heat capacity for concrete masonry walls is to multiply the wall weight per square foot by 0.2, which is the approximate specific heat for concrete masonry materials.

5.2.3 Thermal resistance insulation—The physical loca-tion of wall insulation relative to wall mass also significantly affects thermal performance. In concrete masonry walls, insu-lation can be placed on the interior of the wall, integral with the masonry, or on the exterior, where it is the most effective. For maximum benefit from thermal inertia, the mass should be in direct contact with the conditioned air. Because insula-tion on the interior of the mass thermally isolates the mass from the conditioned space, exterior insulation strategies are usually recommended. For example, rigid board insulation applied on the wall exterior, with a finish applied over the insulation, is generally more energy efficient than furring out the interior of a mass wall and installing batt insulation. Integral insulation strategies include insulating the cores of a masonry unit, using an insulated concrete sandwich panel, or insulating the cavity of a double-wythe masonry wall. In these cases, mass is on both sides of the insulation. Integral insulation allows greater thermal inertia benefits than inte-rior insulation, but not as much as exterior insulation.

5.2.4 Daily (diurnal) temperature changes—A structure can be designed for energy savings by using thermal mass to introduce thermal lag, which delays and reduces peak temperatures. Figure 5.2.4(a) illustrates the thermal lag for an 8 in. (200 mm) concrete wall. When outdoor temperatures are at their peak, the indoor air remains relatively unaffected because the outdoor heat has not had time to penetrate the

Table 5.2.2a—Specific heat and/or heat capacity of concrete, masonry, and related materials (in.-lb units)

MaterialDensity,

lb/ft3Thickness,

in.

Specific heat cp, Btu/

(lb·°F)

Heat capacity hc, Btu/(ft2·°F)*

Mortar 120 — 0.20 —Grout 130 — 0.20 —

Concrete

8090100110120130140

———————

0.210.210.210.210/210.210.21

———————

Clay brick, solid 135 3.625 0.20 7.6

Gypsum wallboard

505050

0.3750.5000.625

0.260.260.26

0.410.540.68

Plaster and stucco

120120120

0.3750.5000.625

0.200.200.20

1.01.52.0

Note: Taken from National Concrete Masonry Association (2008).*For heat capacity of concrete masonry single-wythe walls, refer to Tables 5.2.2c and 5.2.2e.

Table 5.2.2b—Specific heat and/or heat capacity of concrete, masonry, and related materials (SI units)

MaterialDensity, kg/

m3Thickness,

mmSpecific heat cp, kJ/(kg·K)

Heat capacity hc,kJ/(m2·K)*

Mortar 1920 — 0.84 —Grout 2080 — 0.84 —

Concrete

1280144016001760192020802240

———————

0.880.880.880.880.880.880.88

———————

Clay brick, solid 2160 92 0.84 49

Gypsum wallboard

800800800

101316

1.091.091.09

2.63.54.4

Plaster and stucco

192019201920

101316

0.840.840.84

6.49.712.9

*For heat capacity of concrete masonry single-wythe walls, refer to Tables 5.2.2d and 5.2.2f.

Note: Taken from National Concrete Masonry Association (2008).

Table 5.2.2c—Heat capacity, Btu/(ft2·°F), of ungrouted hollow single-wythe walls (in.-lb units)

Concrete masonry unit Density of concrete in CMU, lb/ft3*

Nominal thickness,

in.Percent

solid 85 95 105 115 125 135

474 2.7 3.0 3.3 3.6 3.9 4.2

100 5.6 6.2 6.7 7.3 7.9 8.56 55 4.0 4.5 4.9 5.4 5.8 6.28 53 5.2 5.8 6.3 6.9 7.5 8.0

10 46.3 6.0 6.6 7.3 7.9 8.6 9.312 44 6.6 7.3 8.0 8.8 9.5 10.2

Note: Face shell bedding (density of mortar = 120 lb/ft3; specific heat of mortar = 0.20 Btu/(lb·°F). Taken from National Concrete Masonry Association (2008).

Table 5.2.2d—Heat capacity, kJ/(m2·K), of ungrouted hollow single-wythe walls (SI units)

Concrete masonry unit Density of concrete in CMU, kg/m3

Thick-ness, mm

Percent solid 1360 1520 1680 1840 2000 2160

10274 18 20 21 23 25 27100 36 40 44 47 51 55

152 55 26 29 32 35 37 40203 53 34 37 41 45 48 52254 46.3 39 43 47 51 56 60305 44 42 47 52 56 61 66

Note: Face shell bedding (density of mortar = 1920 kg/m3; specific heat of mortar = 0.84 kJ/(kg·K). Taken from National Concrete Masonry Association (2008).





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Table 5.2.2e—Heat capacity, Btu/(ft2·°F), of grouted single-wythe walls (in.-lb units)*Concrete masonry configuration Density of concrete in CMU, lb/ft3*

Nominal thickness, in. Percent solid Grout spacing, in. 85 95 105 115 125 135

6 55

8 11.1 11.6 12.0 12.4 12.9 13.316 7.6 8.0 8.5 8.9 9.3 9.824 6.4 6.8 7.3 7.7 8.2 8.632 5.8 6.2 6.7 7.1 7.6 8.040 5.5 5.9 6.3 6.8 7.2 7.748 5.2 5.7 6.1 6.5 7.0 7.4

8 52

8 15.2 15.8 16.3 16.9 17.5 18.016 10.2 10.8 11.1 11.9 12.5 13.124 8.5 9.1 9.7 10.3 10.8 11.432 7.7 8.3 8.8 9.4 10.0 10.540 7.2 7.8 8.3 8.9 9.5 10.048 6.9 7.4 8.0 8.6 9.1 9.7

10 48

8 19.5 20.1 20.8 21.5 22.1 22.816 12.8 13.4 14.1 14.7 15.4 16.024 10.5 11.2 11.8 12.5 13.1 13.832 9.4 10.0 10.7 11.3 12.0 12.740 8.7 9.3 10.0 10.7 11.3 12.048 8.2 8.9 9.5 10.2 10.9 11.5

12 48

8 23.9 24.6 25.3 26.1 26.8 27.516 15.3 16.0 16.7 17.4 18.2 18.924 12.4 13.1 13.8 14.5 15.3 16.032 10.9 11.6 12.4 13.1 13.8 14.640 10.0 10.8 11.5 12.2 13.0 13.748 9.5 10.2 10.9 11.7 12.4 13.1

Note: Face shell bedding (density of mortar = 120 lb/ft3; specific heat of mortar = 0.20 [Btu/lb·°F]). Taken from National Concrete Masonry Association (2008).

Table 5.2.2f—Heat capacity, kJ/(m2·K), of grouted single-wythe walls (SI units)Concrete masonry configuration Density of concrete in CMU, kg/m3*

Thickness, in. Percent solid Grout spacing, mm 1360 1520 1680 1840 2000 2160

152 55

203 72 75 77 80 83 86406 49 52 55 57 60 63610 41 44 47 50 53 55813 38 40 43 46 49 52

1016 35 38 41 44 47 491219 34 37 39 42 45 48

203 52

203 98 102 105 109 113 116406 66 70 73 77 81 84610 55 59 62 66 70 73813 50 53 57 61 64 68

1016 47 50 54 58 61 651219 44 48 52 55 59 63

254 48

203 126 130 134 139 143 147406 82 87 91 95 99 104610 68 72 76 80 85 89813 60 65 69 73 77 82

1016 56 60 65 69 73 771219 53 57 62 66 70 74

305 48

203 154 159 164 168 173 178406 98 103 108 113 117 122610 80 84 89 94 99 103813 70 75 80 85 89 94

1016 65 70 74 79 84 881219 61 66 70 75 80 85

Notes: Face shell bedding (density of mortar = 1920 kg/m3; specific heat of mortar = 0.84 kJ/(kg·K). Taken from National Concrete Masonry Association (2008).





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mass. By nightfall, when outside temperatures are falling, the mass of the exterior wall begins to release the heat stored during the day, moderating its effect on the interior condi-tioned space. Temperature amplitudes are reduced and never reach the extremes of the outdoor temperatures. Figure 5.2.4(a) represents an ideal climate condition for thermal inertia in which large outdoor daily temperature swings do not create uncomfortable indoor temperatures due to the mass wall’s ability to moderate heat flow into the building. Thermal inertia benefits are greater in seasons having large daily temperature swings, as can occur during the spring and fall. In cold climates, thermal mass can be used to collect and store solar energy and internal heat gains generated by office and mechanical equipment. These thermal gains are later reradiated into the conditioned space, thus reducing the heating load. During the cooling season, these same solar and internal gains can be dissipated using night-ventilation strategies (circulating cooler outdoor air over the mass mate-rials or walls). The night venting cools the thermal mass, allowing the interior of the building to remain cool well into the day, reducing the cooling loads and potentially shifting peak loads.

5.2.5 Solar reflectance—Generally, materials that appear to be light in color within the visual spectrum have a high solar reflectance and those that appear dark have a low solar reflectance. However, color is not always a reliable indicator of solar reflectance because color only represents 47 percent of the energy in the solar spectrum. New concrete without added pigments for color generally has a solar reflectance of at least 0.30. Concrete made with slag cement or white port-land cement has a higher reflectance, up to 0.70 (Marceau and VanGeem 2007). Solar reflectance is typically measured using ASTM C1549 or E1918.

5.2.6 Solar reflectance index—The solar reflective index of new concrete without added pigments for color is gener-ally at least 29. Concrete with slag cement or white port-land cement has higher solar reflectance indexes, up to 85 (Marceau and VanGeem 2007). The calculated solar reflec-tance index for a material is typically determined using the procedure provided in ASTM E1980.

5.2.7 Building design—Building design and use can impact thermal inertia because different buildings use energy in different ways. In many low-rise residential build-ings, especially those with low percentages of fenestration, heating and cooling are primarily influenced by the thermal performance of the building envelope. These buildings are said to have skin-dominated thermal loads, and the effects of exterior thermal inertia for low-rise residential buildings are influenced primarily by climate and wall construction.

On the other hand, the thermal inertia of commercial and high-rise residential buildings is significantly affected by internal heat gains in addition to the climate and wall construction. Large internal heat gains from lighting, equip-ment, occupants, and solar transmission through windows create a greater need for interior thermal inertia to absorb heat and delay heat flow. Also, commercial buildings gener-ally have peak cooling loads in the afternoon and have low or no occupancy in the evening. Therefore, delaying the

peak load from the afternoon to the evening saves substan-tial energy because the peak then occurs when the building is unoccupied and the heating, ventilating, and air conditioning (HVAC) system can be shifted to nighttime or off-peak oper-ation. As a result, the benefits of thermal inertia are generally greater for commercial and high-rise residential buildings than for low-rise residential buildings.

5.3—Determining thermal inertia effectsPhysical testing and computer simulations may be used to

estimate the dynamic thermal performance of concrete and masonry walls and buildings. The calibrated hot box (ASTM C1363) can be used to determine the dynamic thermal performance of concrete and masonry wall sections. These tests, however, are usually limited to 8 ft2 (0.74 m2) sections of the opaque wall. A computer is needed to simulate the complex interactions of all building envelope components under constantly varying climatic conditions.

5.3.1 Calibrated hot-box test—The calibrated hot-box test is used to determine the static and dynamic response of wall specimens to indoor and outdoor temperatures. The hot box consists of two highly insulated chambers clamped tightly together to surround the test wall. Air in each chamber is conditioned by heating and cooling equipment to obtain desired temperatures on each side of the test wall.

Fig. 5.2.4—(a) Thermal lag for 8 in. (200 mm) concrete wall; and (b) thermal lag and amplitude reduction for 8 in. (200 mm) concrete wall.





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The outdoor (climatic) chamber is cycled between various temperatures. These temperature cycles can be programmed to simulate outdoor daily temperature swings. The indoor (metering) chamber is typically maintained at a constant temperature between 65 and 80°F (18 and 27°C) to simulate indoor room conditions.

The chambers and test specimens are instrumented to monitor air and surface temperatures on both sides of the test wall and heating energy input to the indoor chamber. Instru-ments monitor the energy required to maintain a constant indoor temperature while the outdoor temperature is varied. This energy, when corrected for small thermal losses through the frame, provides a measure of transient heat flow through the test wall.

The calibrated hot box is used to quantify the time lag between outdoor and indoor peak temperatures and the reduction in peak temperatures from outside to inside. The time lag shows the response time of a mass wall to outdoor temperature fluctuations. A long time lag and amplitude reduction minimize cycling of the HVAC equipment and increase system efficiency. Additional cost savings can result where utility companies offer reduced off-peak energy rates. With a reduction in peak temperatures, less cooling capacity is needed, and the cooling capacity of the HVAC system can frequently be reduced. Similar savings occur for heating. Thermal lag depends on the R-value as well as the heat capacity because both of these factors influence the rate of heat flow through a wall.

Two methods of measuring thermal lag use the cali-brated hot box. In one method, denoted to versus ti, thermal lag is calculated as the time required for the maximum (or minimum) indoor surface temperature ti to be reached after the maximum (or minimum) outdoor air temperature to is attained (Fig. 5.2.4(a)). In the second method, denoted qss versus qw, thermal lag is calculated as the time required for the maximum (or minimum) heat flow rate qw to be reached after the maximum (or minimum) heat flow rate based on steady-state predictions, qss, is attained (Fig. 5.2.4(b)). The reduction in amplitude due to thermal inertia is defined as the percent reduction in peak heat flow from calibrated

hot-box tests when compared with peak heat flow predicted by steady-state analysis. Reduction in amplitude, such as thermal lag, is dependent on the heat-storage capacity and thermal resistance of the wall, as well as climate. Amplitude reduction for concrete and masonry walls varies between 20 and 60 percent (Childs et al. 1983; Fiorato 1981; Fiorato and Bravinsky 1981; Fiorato and Cruz 1981; Peavy et al. 1973; VanGeem 1984, 1986a,b; VanGeem and Fiorato 1983; VanGeem and Larson 1984).

Table 5.3.1 shows values of thermal lag and amplitude reduction for various walls when cycled using an outside temperature cycle representative of the specific climate during a specific time period. Other temperature cycles, representative of different climates, will give different results. The test results provided in Table 5.3.1 are intended solely to demonstrate the variations in time lag and ampli-tude reduction for various wall assemblies and are based on sol-air diurnal temperature ranges representative of April or May in Gaithersburg, MD. Sol-air temperature is that temperature of outdoor air that, in the absence of all radia-tion exchanges, would give the same rate of heat entry into the surface as would exist with actual combination of inci-dent solar radiation, radiant energy exchange, and convec-tive heat exchange with outdoor air.

5.3.2 Computer simulations of buildings—Computer programs have been developed to simulate the thermal performance of buildings and to predict heating and cooling loads. These programs account for material properties of the building components and the buildings’ geometry, orienta-tion, solar gains, internal gains, and temperature-control strategy. Calculations can be performed on an hourly basis using a full year of weather data for a given location. Several public domain computer simulation programs have been well-documented and validated through comparisons with monitored results from test cells and full-scale build-ings (U.S. Department of Energy 2009, 2010). Although results of such computer analyses will probably not agree completely with actual building performance, relative values between computer-modeled buildings and the corresponding actual buildings are in good agreement.

Table 5.3.1—Thermal lag and amplitude reduction measurements from calibrated hot box testsWall no. Thermal lag, h Amplitude change, %

7.625 x 7.625 x 15.625 in. (194 x 194 x 397 mm) masonry 3.0 –187.625 x 7.625 x 15.625 in. (194 x 194 x 397 mm) masonry, with insulated cores. 3.5 –284-2-4 masonry cavity wall with actual dimensions of 3.625 – 2.750 – 3.625 in. (92 – 70 – 92 mm) 4.5 –404-2-4 insulated masonry cavity wall with actual dimensions of 3.625 – 2.750 – 3.625 in. (92 – 70 – 92 mm) 6.0 –38Finished 7.625 x 7.625 x 15.625 in. (194 x 194 x 397 mm) masonry wall 3.0 –51Finished 7.625 x 7.625 x 15.625 in. (194 x 194 x 397 mm) masonry wall with interior insulation 4.5 –31Finished 5.625 x 7.625 x 15.625 in. (143 x 194 x 397 mm) masonry wall with interior insulation 3.5 –10Finished 7.625 x 3.625 x 15.625 in. (194 x 92 x 397 mm) masonry wall with interior insulation 4.5 –27Structural concrete wall 4.0 –45Structural lightweight concrete wall 5.5 –53Low-density concrete wall 8.5 –61Finished, insulated nominal 2 x 4 in. (38 x 89 mm) wood frame wall 2.5 6Finished, insulated nominal 2 x 4 in. (38 x 89 mm) wood frame wall 1.5 –7.5Finished, insulated nominal 2 x 4 in. (38 x 89 mm) wood frame wall 1.5 4Insulated nominal 2 x 4 in. (38 x 89 mm) wood frame wall with a masonry veneer 4.0 6





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5.4—Equivalent R-values for concrete and masonry walls

5.4.1 Equivalency—Studies of entire buildings by various laboratories show that concrete and masonry buildings of large thermal inertia have lower annual heating and cooling loads than other similarly insulated buildings (Peavy et al. 1972, 1973; Petersen and Barnett, 1980; Petersen et al. 1981). Therefore, concrete or masonry buildings require less insulation for equivalent performance than buildings with less thermal inertia, such as wood or steel stud framing.

Proposed building designs are generally considered to be in compliance with energy codes and standards as long as the proposed building design will not use more energy than the same building designed according to the prescrip-tive requirements of the building code or energy code of the jurisdiction. For this compliance procedure, the building is analyzed using the prescribed U-values or R-values listed in the jurisdiction’s building or energy code to determine the estimated annual energy load. Where prescriptive require-ments of building and energy codes do not address param-eters, such as thermal inertia and day lighting, such param-eters may be incorporated. The resulting energy load that includes these factors is then determined. If this new load is less than the load due to the prescriptive requirements, the building component U-values can be increased until the loads are equivalent. This may be accomplished through repetitive computer simulations. However, such simulations may be costly and may only be deemed economical for large buildings.

5.4.2 Building and energy code requirements—Most energy codes and standards account for thermal inertia of

mass walls by requiring different R-values and U-factors for frame wall and mass wall construction. The criteria, developed using computer simulations, are dependent on the climate, building type (low-rise residential or buildings other than low-rise residential), properties and amount of fenestration, and properties of the mass wall including posi-tion of the insulation. Most code provisions developed to date in the United State reflect the cost of adding insulation to the wall assembly. Where economics are introduced, the analyses may generate values not truly representative of the benefits of thermal inertia alone. Analyses, including the cost of adding insulation, were used to develop the require-ments in the most widely adopted model building codes, energy codes, and reference standards used in the United States (ANSI/ASHRAE/IES 90.1; ANSI/ASHRAE/IES 90.2; ICC 2009, 2012). Examples of the adjustments to U-values for mass wall systems for determining compliance with building codes and referenced standards are provided in Tables 5.4.2a and 5.4.2b. The adjustments are relative to maximum permissible U-values for wood frame and light gauge steel frame above-grade wall assemblies.

5.5—Interior thermal inertiaUp to this point, most of the information presented in

this chapter has focused on the effects of thermal inertia in the exterior envelopes of buildings. Concrete and masonry can also help improve building occupant comfort and save additional energy when used in building interiors. When designing interior mass components, steady-state heat flow is usually not important because there is typically no significant heat transfer through an interior wall or floor.

Table 5.4.2a––Examples of adjustment for thermal inertia in equivalent U-values, Btu/(h·ft2·°F) (in.-lb units)

Climate zone*

Residential except low-rise† All buildings except residential‡

Wood stud wall Metal stud wall Mass wall§ Wood stud wall Metal stud wall Mass wall1 0.082 0.082 0.197 0.064 0.077 0.1422 0.082 0.082 0.165 0.064 0.077 0.1423 0.057 0.057 0.098 0.064 0.064 0.110

4 except marine 0.057 0.057 0.098 0.064 0.064 0.1044 marine and 5 0.057 0.057 0.082 0.064 0.064 0.078

6 0.048 0.048 0.060 0.051 0.064 0.0787 0.048 0.048 0.057 0.051 0.064 0.0618 0.048 0.048 0.057 0.036 0.045 0.061

*Climates zones are based on temperature and moisture and indicated on appropriate maps in the respective standards and codes. Generally, the climate zones with the lower numbers are for warmer climates. Most states contain multiple climate zones:

AK – 7, 8 HI – 1 ME – 6, 7 NJ — 4,5 SD – 5, 6

AL – 2, 3 IA – 5, 6 MI – 5, 6, 7 NM – 3, 4, 5 TN – 3, 4

AR – 3, 4 ID – 5, 6 MN – 6, 7 NV – 3, 5 TX – 2, 3, 4

AZ – 2, 3, 4, 5 IL – 4, 5 MO – 4, 5 NY – 5, 6 UT – 5, 6

CA – 3, 4, 5, 6 IN – 4, 5 MS – 2, 3 OH – 4, 5 VA – 4

CO – 4, 5, 6, 7 KS – 4, 5 MT – 6 OK – 3, 4 VT – 6

CT – 5 KY – 4 NC – 3, 4, 5 OR – 4, 5 WA – 4, 5, 6

DC – 4 LA – 2, 3 ND – 6, 7 PA – 4, 5, 6 WI – 6, 7

DE – 4 MA – 5 NE – 5 RI – 5 WV – 4, 5

FL – 1, 2 MD – 4, 5 NH – 5, 6 SC – 3 WY – 5, 6, 7

GA – 2, 3, 4†From Table R402.1.3 in IECC (2012).‡From Table C402.1.2 in IECC (2012).§With exterior or integral insulation.





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Instead, heat is absorbed from the room into the mass then re-released back into the room. In other words, the interior mass acts as a storage facility for energy. A concrete floor in a sunroom absorbs solar energy during the day, then releases the stored warmth during the cooler nighttime hours. Simi-larly, it can absorb heat generated from occupants, equip-ment, appliances, and lights. Further, because most concrete and masonry constructions are absorbent, latent loads due to moisture can also be absorbed.

Thermal inertia resulting from placement of concrete and masonry inside the building envelope reduces interior temperature fluctuations. These diurnal or seasonal reduc-tions are commonly referred to as the flywheel effect because the temperature inside a building changes more slowly with respect to the exterior temperature fluctuations than would occur in a building without interior mass. This keeps the building from cooling too fast at night during the heating season or heating too quickly during the day in the cooling season.

To use interior thermal inertia effectively, carefully choose the heat capacity and properly locate the concrete and masonry components. Concrete or masonry as thin as 3 in. (75 mm) is generally sufficient to moderate diurnal interior temperature fluctuations because surface area is more important than thickness for interior thermal inertia. A large surface area in contact with conditioned air tends to stabilize interior temperatures. Concrete or masonry distributed in a thin layer over the walls and floors of inte-rior rooms is more effective than the same amount of mass placed in one thick, solid thermal inertia wall. Other designs may require different placements of thermal inertia (Balik

and Barney 1981a,b,c; Balik and Barney 1983; Catani and Goodwin 1976, 1977; Goodwin and Catani 1979a,b; Mitalas 1979; Portland Cement Association 1981, 1982; Rudoy and Dougall 1979). For passive solar applications, the mass should be in direct contact with the sunlight for maximum effectiveness (Total Environment Action, Inc. 1980).

CHAPTER 6—THERMAL PROPERTIES FOR PASSIVE SOLAR DESIGN

6.1—IntroductionPassive solar buildings use three basic components:

glazing, thermal inertia, and ventilation. South-facing glass, typically within 45 degrees of true south, is used as the heat collector. Glass in other parts of the building is minimized to reduce heat loss or unwanted heat gain. Thermal inertia is used to store heat gained through the glass and to maintain interior comfort. The building ventilation system distributes air warmed by solar gains throughout the building (Brick Industry Association 1980; Mazria 1979). The amount, configuration, and placement of the thermal storage media will be influenced by the type of passive solar design—direct gain, indirect gain, and remote storage systems.

Passive solar buildings, especially in colder climates, tend to require more thermal inertia to adequately store solar gains and maintain comfort in both heating and cooling seasons. The heat-storage capacity of concrete and masonry materials is determined by a variety of thermal proper-ties such as absorptivity, conductivity, specific heat, diffu-sivity, and emissivity. This chapter describes these proper-ties, discusses their impact on passive solar buildings, and

Table 5.4.2b––Examples of adjustment for thermal inertia in equivalent U-values, W/(m·K) (SI units)

Climate zone*

Residential except low-rise† All buildings except residential‡

Wood stud wall Metal stud wall Mass wall§ Wood stud wall Metal stud wall Mass wall1 0.466 0.466 1.119 0.364 0.437 0.8072 0.466 0.466 0.937 0.364 0.437 0.8073 0.324 0.324 0.557 0.364 0.364 0.625

4 except marine 0.324 0.324 0.557 0.364 0.364 0.5914 marine and 5 0.324 0.324 0.466 0.364 0.364 0.443

6 0.273 0.273 0.341 0.290 0.364 0.4437 0.273 0.273 0.324 0.290 0.364 0.3468 0.273 0.273 0.324 0.204 0.256 0.346

*Climates zones are based on temperature and moisture and indicated on appropriate maps in the respective standards and codes. Generally the climate zones with the lower numbers are for warmer climates. Most states contain multiple climate zones:

AK – 7, 8 HI – 1 ME – 6, 7 NJ — 4,5 SD – 5, 6

AL – 2, 3 IA – 5, 6 MI – 5, 6, 7 NM – 3, 4, 5 TN – 3, 4

AR – 3, 4 ID – 5, 6 MN – 6, 7 NV – 3, 5 TX – 2, 3, 4

AZ – 2, 3, 4, 5 IL – 4, 5 MO – 4, 5 NY – 5, 6 UT – 5, 6

CA – 3, 4, 5, 6 IN – 4, 5 MS – 2, 3 OH – 4, 5 VA – 4

CO – 4, 5, 6, 7 KS – 4, 5 MT – 6 OK – 3, 4 VT – 6

CT – 5 KY – 4 NC – 3, 4, 5 OR – 4, 5 WA – 4, 5, 6

DC – 4 LA – 2, 3 ND – 6, 7 PA – 4, 5, 6 WI – 6, 7

DE – 4 MA – 5 NE – 5 RI – 5 WV – 4, 5

FL – 1, 2 MD – 4, 5 NH – 5, 6 SC – 3 WY – 5, 6, 7

GA – 2, 3, 4†From Table R402.1.3 in IECC (2012).‡From Table C402.1.2 in IECC (2012).§With exterior or integral insulation.





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provides design values. These data allow designers to more accurately predict the performance of thermal storage mass and to choose appropriate materials for a particular design.

6.2—Thermal propertiesThermal properties of the storage mass must be known to

size HVAC equipment, to maintain comfort in the building, and to determine the optimal amount and arrangement of the mass. For most passive solar applications where the thermal loads are primarily skin-dominated, heat energy absorbed during the day is preferably used at night as opposed to the next day. Therefore, the thermal inertia storage effectiveness depends on the heat-storage capacity of the mass and the rate of heat flow through the mass. The thermal storage capa-bility is influenced by the thermal properties of the storage media. These properties are thickness, absorptivity, emis-sivity, and diffusivity (diffusivity is related to conductivity, density, and specific heat).

6.2.1 Effects of conductivity—Conductivity indicates how quickly or easily heat flows through a material. In passive solar applications, conductivity allows the solar heat to be transferred beyond the surface of the mass for more effec-tive storage. Materials with very high conductivity values, however, should be avoided because high conductivity can shorten the time lag for heat delivery.

6.2.2 Effects of absorptivity—The amount of heat absorbed by a wall depends on its absorptivity and the solar radia-tion incident on the wall. Absorptivity is a measure of the efficiency of receiving radiated heat and is the fraction of incident solar radiation that is absorbed by a given mate-rial, as opposed to being reflected or transmitted. For opaque materials, such as concrete and masonry, solar radiation not absorbed by the wall is reflected away from it. Absorptivity is a relative value; an absorptivity of 1.0 indicates that a material absorbs all incident radiated heat and reflects none.

The absorptivity of nonmetallic materials is a surface effect largely dependent on surface color. Dark surfaces have higher absorbtivities than light surfaces because they absorb more heat, while light surfaces reflect more heat than they absorb.

Sunlit thermal-mass floors should be relatively dark in color to absorb and store heat more efficiently. Robinson (1980) concludes that reds, browns, blues, and blacks will perform adequately for passive solar storage. Nonmass walls and ceilings should be light in color to reflect solar radiation to the thermal storage mass and to help distribute light more evenly.

Rough-textured surfaces, such as split-faced concrete masonry or stucco, provide more surface area for collection of solar energy than smooth surfaces, but this advantage in solar energy collection has not been thoroughly investigated. Solar absorptivity is usually determined using ASTM E434. This test subjects a specimen to simulated solar radiation. Radiant energy absorbed by a specimen and emitted to the surroundings causes the specimen to reach an equilibrium temperature that is dependent on the ratio of absorptivity to emissivity. Solar absorptivity is then determined from the known emissivity.

6.2.3 Effects of emissivity—Emissivity, sometimes called emittance, describes how efficiently a material transfers energy by radiation heat transfer or how efficiently a mate-rial emits energy. Like absorptivity, emissivity is a unitless value defined as the fraction of radiant energy emitted or released from a material relative to the radiation of a perfect emitter or blackbody. For thermal storage, high-emissivity materials are used to effectively release stored solar heat into the living areas.

The ability of a material to emit energy increases as the temperature of the material increases. Therefore, emissivity is a function of temperature and increases with increasing temperature. For the purposes of passive solar building design, emissivity values at room temperature are used. Mazria (1979) and other researchers frequently assume an emissivity value of 0.90 for all nonmetallic building materials.

Emissivity is determined using either emitter or receiver methods. An emitter method involves measuring the amount of energy required to heat a specimen and the temperature of the specimen. A receiver method such as ASTM E408 measures emitted radiation directed into a sensor.

6.2.4 Effects of specific heat—Materials with high specific heat values are effectively used for thermal storage. For values of specific heat for concrete and masonry, refer to Table 5.2.2a.

6.2.5 Effects of heat capacity—Some heat-capacity storage is present in all parts of buildings, including the framing, gypsum board, furnishings, and floors. Home furnishings typically have a specific heat of approximately 0.18 Btu/(h·°F) (754 J/(kg·K)). A larger amount of thermal inertia, however, is required in passive solar buildings and buildings designed to use thermal inertia to reduce energy loads or shift loads to off-peak hours. Walls and floors with high heat capacities are desirable for thermal storage appli-cations. Heat capacity is discussed in 5.2.2.

6.2.6 Effects of thermal diffusivity—Thermal diffusivity is a measure of heat transport relative to energy storage and is defined in 5.2.1. Materials with high thermal diffusivities are more effective at heat transfer than heat storage. There-fore, materials with low thermal diffusivities are desirable for storing solar energy.

6.3—Incorporating mass into passive solar designs

6.3.1 Passive solar designs—In addition to the material properties discussed herein, location of thermal mass mate-rials is also important in passive solar applications. There are four commonly-used passive solar designs: direct gain, indirect gain, remote storage, and natural cooling systems. The most common of these are direct gain passive solar systems. Direct gain systems are those where solar energy penetrates directly into the space where it is stored and used. Because the collection area is occupied space, it is impor-tant that the temperature remain within the comfort range of the occupants, and the use of thermal mass materials can achieve this. Indirect gain systems use a thermal mass mate-rial between the glazing and the occupied space to be heated





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to collect, store, and distribute solar radiation (such as a trombe wall). In a remote storage system, the solar energy is collected in an area that can be closed off from the rest of the building. These systems use thermal mass materials for thermal storage as well as a heat transfer valve between the collection area and the occupied space. The fourth type of passive solar design involves the use of solar heating and chimney effects to provide enhanced natural cooling. The thermal inertia components for such systems will tend to be remote or indirect gain systems.

The configuration and placement of thermal mass for indi-rect gain, remote storage, and natural cooling passive solar systems tend to be complex and typically must be deter-mined knowing the capabilities of the specific HVAC system being used for the project. Thus, little or no guidance for the design of indirect gain, remote storage, and natural cooling systems is provided herein.

6.3.2 Direct gain passive solar systems—For most concrete and masonry materials, the effectiveness of thermal inertia in the floor or interior wall increases proportionally with a thickness up to approximately 3 to 4 in. (75 to 100 mm). Beyond that, the effectiveness for use in diurnal direct gain systems does not increase as significantly. A nominal 4 in. (100 mm) thick mass floor is approximately 30 percent more effective at storing direct sunlight than a nominal 2 in. (50 mm) thick mass floor. A nominal 6 in. (150 mm) thick mass floor, however, will only perform approximately 8 percent better than the nominal 4 in. (100 mm) floor. For most direct gain applications, nominal 3 to 4 in. (75 to 100 mm) thick mass walls and floors maximize the amount of storage per unit of wall or floor material, unless thicker elements are required for structural or other considerations. In direct gain passive solar applications, distributing thermal inertia evenly around a room stores heat more efficiently and improves comfort by reducing localized hot or cold spots.

6.3.3 Other considerations—Location of thermal mass within a passive solar building is also important in deter-mining a building’s efficiency and comfort. Mass located in the space where solar energy is collected is approximately four times more effective than mass located outside the collection area. If the mass is located away from the sunlit area, it is considered to be convectively coupled. Such a configuration provides a mechanism for storing heat away from the collection area through natural convection and improves comfort by damping indoor temperature swings.

Covering mass walls and floors with materials having R-values larger than approximately 0.5 (h·ft2·°F)/Btu (0.09 (m2·K)/W) and low thermal diffusivities will reduce the daily heat-storage capacity. Coverings such as surface bonding, thin plaster coats, stuccos, and wallpapers do not significantly reduce the storage capacity. Materials such as cork, paneling with furring, and sound boards are best avoided. Direct attachment of gypsum board is acceptable if it is firmly adhered to the concrete, concrete masonry, or clay masonry wall surface (no air space between gypsum board and masonry). Exterior mass walls should be insulated on the exterior or within the cores of concrete masonry to maxi-mize the effectiveness of the thermal inertia. Thermal inertia

can easily be incorporated into the floors of many buildings using slab-on-ground or hollow precast floors. If mass is used in floors, it will be much more effective if sunlight falls directly on it. Effective materials for floors include painted, colored, or vinyl-covered concrete; brick or concrete pavers; quarry tile; and dark-colored ceramic tile.

As more south-facing glass is used, more thermal inertia should be provided to store heat gains and prevent the building from overheating. Although the concept is simple, in practice the relationship between the amount of glazing and the amount of mass is complicated by many factors. From a comfort standpoint, it would be difficult to add too much mass. Thermal inertia will hold solar gains longer in winter and keep buildings cooler in summer. Design guid-ance on passive solar buildings is beyond the scope of this guide. More information on passive solar building design can be found in Mazria (1979).

6.4—SummaryPassive solar buildings represent a specialized application

of thermal inertia for solar heat storage, retention, and reradi-ation. To accomplish these tasks, the storage medium should have certain thermal characteristics. Thermal conductivity should be high enough to allow the heat to penetrate into the storage material but not so high that the storage time or thermal lag is shortened. Solar absorptivity should be high, especially for mass floors, to maximize the amount of solar energy that can be stored.

Thermal storage materials should have high-emissivity characteristics to efficiently reradiate the stored energy back into the occupied space. Specific heat and heat capacity should be high to maximize the amount of energy that can be stored in a given amount of material.

Concrete and masonry materials fulfill all of these require-ments for effective thermal storage. These materials have been used with great success in passive solar buildings to store the collected solar energy, prevent overheating, and reradiate energy to the interior space when needed.

CHAPTER 7—CONDENSATION CONTROL

7.1—IntroductionMoisture condensation on the interior surfaces of a building

envelope is unsightly and can cause damage to the building or its contents. Moisture condensation within a building wall or ceiling assembly can be even more undesirable because it may not be noticed until damage has occurred.

All air contains water vapor, and warm air carries more water vapor than cold air. Moisture, in the form of water vapor, is added to the air by respiration, perspiration, bathing, cooking, laundering, humidifiers, and industrial processes. When moist air contacts cold surfaces, the air may be cooled below its dew point, permitting condensation to occur. Dew point is the temperature at which water vapor condenses.

Once the dew point is reached, the relative humidity of the interior space of a building should not be increased because any additional increase in relative humidity will increase the potential amount of condensate on the cold surface. The





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inside surface temperature of a building assembly effec-tively limits the design relative humidity of air contained in an interior space to prevent condensation.

7.2—Prevention of condensation on wall surfaces under steady-state analysis

Condensation on interior surfaces can be prevented by using materials with U-values such that the surface tempera-ture will not fall below the dew point temperature of the air in the room. The amount of thermal resistance that should be provided to avoid condensation can be determined from the following relationship

R R

t tt tt ii o

i s

=−−

( ) (7.2a)

Due to lag time associated with the thermal inertia effect, the steady-state analysis of condensation is conservative for masonry walls. Dew point temperatures to the nearest degree Fahrenheit for various values of ti and relative humidity are shown in Table 7.2a (Celsius in Table 7.2b).

For example, Rt is to be determined when the room temper-ature and relative humidity are 70°F (21°C) and 40 percent, respectively, and to during the heating season is –10°F (–24°C). From Table 7.2a and 7.2b, the dew point tempera-ture ts is 45°F (7°C) and, because the resistance of the inte-

rior air film, Ri, is 0.68 (h·ft2·°F)/Btu (0.12 (m2·K)/W), the thermal resistance of the insulating layer is as follows

Rt = 0.68 × [70 – (–10)]/(70 – 45) = 2.18 (h·ft2·°F)/Btu (0.38 (m2·K)/W) (7.2b)

7.3—Prevention of condensation within wall constructions

Water vapor in air diffuses through building materials at rates that depend on vapor permeabilities of materials and vapor-pressure differentials. Colder outside air temperatures increase the water-vapor-pressure differential with the warm inside air; this increases the driving force moving the inside air to the outside.

Leakage of moisture-laden air into an assembly through small cracks can be a greater problem than vapor diffusion. The passage of water vapor through a material is, in itself, generally not harmful. It becomes of consequence when, at some point along the vapor flow path, vapors fall below the dew point temperature and condense.

Water-vapor permeability and permeances of some building materials are shown in Table 7.3a and 7.3b. When properly used, low-permeability materials keep moisture from entering a wall or roof assembly, whereas high-perme-ability materials allow moisture to escape. When a material such as plaster or gypsum board has a permeance too high for the intended use, one or two coats of paint are often enough

Table 7.2a—Dew-point temperatures ts,* °F (in.-lb units)Dry bulb or room temperature, °F

Relative humidity, %10 20 30 40 50 60 70 80 90 100

40 –7 6 14 19 24 28 31 34 37 4045 –3 9 18 23 28 32 36 39 42 4550 –1 13 21 27 32 37 41 44 47 5055 5 17 26 32 37 41 45 49 52 5560 7 21 30 36 42 46 50 54 57 6065 11 24 33 40 46 51 55 59 62 6570 14 27 38 45 51 56 60 63 67 7075 17 32 42 49 55 60 64 69 72 7580 21 36 46 54 60 65 69 73 77 8085 23 40 50 58 64 70 74 78 82 8590 27 44 55 63 69 74 79 83 85 90

*Temperatures are based on barometric pressure of 29.92 in. Hg2.

Table 7.2b—Dew-point temperatures ts,* °C (SI units)Dry bulb or room temperature, °C

Relative humidity, %10 20 30 40 50 60 70 80 90 100

4 –24 –16 –11.3 –8.1 –5.0 –2.5 –0.6 1.3 3.1 5.07 –22 –14 –8.8 –5.6 –2.5 0.0 2.5 4.4 6.3 8.110 –21 –112 –6.9 –3.1 0.0 3.1 5.6 7.5 9.4 1113 –17 –9.4 –3.8 0.0 3.1 5.6 8.1 11 13 1416 –16 –6.9 –1.3 2.5 6.3 8.8 11 14 16 1818 –13 –5.0 0.6 5.0 8.8 12 14 17 19 2121 –11 –3.1 3.8 8.1 12 15 18 19 22 2424 –9.4 0.0 6.3 11 14 17 20 23 25 2727 –6.9 2.5 8.8 14 18 20 23 26 28 3029 –5.6 5.0 11 16 20 23 26 29 31 3332 –3.1 7.5 14 19 23 26 29 32 33 36

*Temperatures are based on barometric pressure of 101.3 KPa.





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to lower the permeance to an acceptable level. Alternatively, a vapor retarder can be used directly behind such products.

Polyethylene sheet, aluminum foil, and roofing materials are commonly used as vapor retarders. Proprietary vapor retarders, usually combinations of foil, polyethylene, and asphalt, are frequently used in freezer and cold-storage construction. The properties of concrete contribute to the

resistance of vapor transmission. Concrete and masonry assemblies of sufficient thickness, depending on their mate-rial properties, can act as vapor retarders. Permeance is a function of the w/cm of the concrete. A low w/cm results in concrete with low permeance.

Where climatic conditions demand insulation, a vapor retarder is generally needed to prevent condensation. Closed-cell insulation, if properly applied, will serve as its own vapor retarder but should be taped at all joints to be effective. For other insulation materials, a vapor retarder should be applied to the warm side of the insulation for the season representing the most serious condensation poten-tial—that is, on the interior in cold climates and on the exte-rior in hot and humid climates. Low-permeance materials on both sides of insulation, creating a double vapor retarder, can trap moisture within an assembly and should be avoided.

CHAPTER 8—REFERENCESCommittee documents are listed first by document number

and year of publication followed by authored documents listed alphabetically.

American National Standards InstituteANSI/ASHRAE/IES 90.1-2013—Energy Standard for

Buildings Except Low-Rise Residential BuildingsANSI/ASHRAE/IES 90.2-07—Energy Efficient Design

of Low-Rise Residential Buildings

ASTM InternationalASTM C29/C29M-09—Standard Test Method for Bulk

Density (“Unit Weight”) and Voids in AggregateASTM C90-14—Standard Specification for Loadbearing

Concrete Masonry UnitsASTM C177-13—Standard Test Method for Steady-State

Heat Flux Measurements and Thermal Transmission Proper-ties by Means of the Guarded-Hot-Plate Apparatus

ASTM C236-89(1993)—Standard Test Method for Steady-State Thermal Performance of Building Assemblies by Means of a Guarded Hot Box (withdrawn 2001)

ASTM C1363-11—Standard Test Method for Thermal Performance of Building Materials and Envelope Assem-blies by Means of a Hot Box Apparatus

ASTM C1549-09—Standard Test Method for Determina-tion of Solar Reflectance Near Ambient Temperature Using a Portable Solar Reflectometer

ASTM E408-13—Standard Test Methods for Total Normal Emittance of Surfaces Using Inspection-Meter Techniques

ASTM E434-10—Standard Test Method for Calorimetric Determination of Hemispherical Emittance and the Ratio of Solar Absorptance to Hemispherical Emittance Using Solar Simulation

ASTM E1918-06—Standard Test Method for Measuring Solar Reflectance of Horizontal and Low-Sloped Surfaces in the Field

ASTM E1980-11—Standard Practice for Calculating Solar Reflectance Index of Horizontal and Low Sloped Opaque Surfaces

Table 7.3a—Typical permeance M and permeability μ values (in.-lb units)*

Material M, perms μ, perm-in.Concrete (1:2:4 mixture)† 3.2

Wood (sugar pine) — 0.4 to 5.4Expanded polystyrene (extruded) — 1.2

Paint—two coatsAsphalt paint on plywood 0.4 —Enamels on smooth plaster 0.5 to 1.5 —

Various primers plus one coat flat oil paint on plaster 1.6 to 3.0 —

Expanded polystyrene (bead) — 2.0 to 5.8Plaster on gypsum lath (with studs) 20.00 —

Gypsum wallboard, 0.375 in. (9.5 mm) 50.00 —Polyethylene, 2 mil (0.05 mm) 0.16 —Polyethylene, 10 mil (0.3 mm) 0.03 —

Aluminum foil, 0.35 mil (0.009 mm) 0.05 —Aluminum foil, 1 mil (0.03 mm) 0.00 —Built-up roofing (hot mopped) 0.00 —

Duplex sheet, asphalt laminated aluminum foil one side 0.002 —

*ASHRAE (2013), Chapter 26, Tables 7 and 8.†Permeability for concrete varies depending on the concrete’s w/c and other factors.

Table 7.3b—Typical permeance M and permeability μ values (SI units)*

Material M, Kg/(Pa·s·m2) μ, Kg/(Pa·s·m)Concrete (1:2:4 mixture)† 4.65E-12

Wood (sugar pine) — 5.81E-13 to 7.85E-12

Expanded polystyrene (extruded) — 1.74E-12Paint—two coats

Asphalt paint on plywood 2.29E-11 —

Enamels on smooth plaster 2.86E-11 to 8.58E-11 —

Various primers plus one coat flat oil paint on plaster

9.15E-10 to 1.72E-11 —

Expanded polystyrene (bead) — 2.91E-12 to 8.43E-12

Plaster on gypsum lath (with studs) 1.14E-09 —Gypsum wallboard, 0.375 in. (9.5

mm) 2.86E-09 —

Polyethylene, 2 mil (0.05 mm) 9.15E-12 —Polyethylene, 10 mil (0.3 mm) 1.72E-12 —Aluminum foil, 0.35 mil (0.009

mm) 2.86E-12 —

Aluminum foil, 1 mil (0.03 mm) 0.00E+00 —Built-up roofing (hot mopped) 0.00E+00 —

Duplex sheet, asphalt laminated aluminum foil one side 1.14E-13 —

*ASHRAE (2013), Chapter 26, Tables 7 and 8.†Permeability for concrete varies depending on the concrete’s w/c and other factors.





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http://www.ansi.org

http://www.astm.org

Authored documentsArnold, P. J., 1969, “Thermal Conductivity of Masonry

Materials,” Journal, Institution of Heating and Ventilating Engineers (London), V. 37, Aug., pp. 101-108, 117.

ASHRAE, 2009, ASHRAE Handbook: Fundamentals, American Society of Heating, Refrigerating and Air-Condi-tioning Engineers, Ann Arbor, MI, 880 pp.

ASHRAE, 2013, ASHRAE Handbook: Fundamentals, American Society of Heating, Refrigerating and Air-Condi-tioning Engineers, Atlanta, GA.

Balik, J. S., and Barney, G. B., 1981a, “The Performance Approach in Determining Required Levels of Insulation in Concrete Roof Systems,” PCI Journal, V. 26, No. 5, Sept.-Oct., pp. 50-64. doi: 10.15554/pcij.09011981.50.64

Balik, J. S., and Barney, G. B., 1981b, “Cost-Effective Energy Conservation Strategies for Masonry Homes in Florida,” Florida Builder, V. 35, No. 12, Tampa, FL, June, pp. 16-19.

Balik, J. S., and Barney, G. B., 1981c, “Analysis of Energy Conservation Alternatives for Concrete Masonry Homes in Arizona,” PCA R&D SN3260, Portland Cement Associa-tion, Skokie, IL, 40 pp.

Balik, J. S., and Barney, G. B., 1983, “Economics of Insu-lating Concrete Walls in Commercial Buildings,” Proceed-ings of the Conference on Energy Conservation in Building Design and Construction, Minneapolis, MN.

Brick Industry Association, 1980, “Brick Passive Solar Heating Systems, Material Properties—Part IV,” BIA Bulletin No. 43D, Sept./Oct.

Campbell-Allen, D., and Thorn, C. P., 1963, “The Thermal Conductivity of Concrete,” Magazine of Concrete Research, V. 15, No. 43, Mar., pp. 39-48.

Catani, M. J., and Goodwin, S. E., 1976, “Heavy Building Envelopes and Dynamic Thermal Response,” ACI Journal Proceedings, V. 73, No. 2, Feb., pp. 83-86.

Catani, M. J., and Goodwin, S. E., 1977, “Thermal Inertia—The Neglected Concept,” The Construction Speci-fier, May.

Childs, K. W.; Corville, G. E.; and Bales, E. L., 1983, “Thermal Mass Assessment,” ORN/CON-97, Oak Ridge National Laboratory, Oak Ridge, TN.

Fiorato, A. E., 1981, “Heat Transfer Characteristics of Walls Under Dynamic Temperature Conditions,” Research and Development Bulletin RD075, Portland Cement Asso-ciation, Skokie, IL, 20 pp.

Fiorato, A. E., and Bravinsky, E., 1981, Heat Transfer Characteristics of Walls under Arizona Temperature Condi-tions, Construction Technology Laboratories, Portland Cement Association, Skokie, IL, 61 pp.

Fiorato, A. E., and Cruz, C. R., 1981, “Thermal Perfor-mance of Masonry Walls,” Research and Development Bulletin RD-071, Portland Cement Association, Skokie, IL, 17 pp.

Goodwin, S. E., and Catani, M. J., 1979a, “Insulation Study Reveals ‘Where to Stop’ for Best Economic Benefits and Energy-Saving,” Dodge Construction News, V. 33, No. 122, June 25, pp. 1-18.

Goodwin, S. E., and Catani, M. J., 1979b, “The Effect of Mass on Heating and Cooling Loads and on Insulation Requirements of Buildings in Different Climates,” ASHRAE Transaction, V. 85, Part I, 869 pp.

Granholm, H., ed., 1961, Proceedings, RILEM Sympo-sium on Lightweight Concrete, Akademiforlaget-Gumperts, Goteborg, 618 pp.

ICC, 2000, “International Energy Conservation Code,” International Code Council, Country Club Hills, IL.

ICC, 2009, “International Energy Conservation Code,” International Code Council, Country Club Hills, IL.

ICC, 2012, “International Residential Code,” Interna-tional Code Council, Country Club Hills, IL.

Institution of Heating and Ventilating Engineers, 1975, “Thermal and Other Properties of Building Structures,” IHVE Guide, Section A3, Institution of Heating and Venti-lating Engineers, London.

Kluge, R. W.; Sparks, M. M.; and Tuma, E. C., 1949, “Lightweight-Aggregate Concrete,” ACI Journal Proceed-ings, V. 45, No. 9, May, pp. 625-644.

Lentz, A. E., and Monfore, G. E., 1965a, “Thermal Conductivity of Concrete at Very Low Temperatures,” PCA Research and Development Laboratories Journal, V. 7, No. 2, May, pp. 39-46.

Lentz, A. E., and Monfore, G. E., 1965b, “Thermal Conductivities of Portland Cement Paste, Aggregate, and Concrete Down to Very Low Temperatures,” PCA Research and Development Laboratories Journal, V. 8, No. 3, Sept., pp. 27-33.

Lewicki, B., 1967, Concrete Architecture: Lightweight Concrete, V. 4, Engineering Committee, Polish Academy of Sciences, Wydawnictwo ARKADY, Warsaw, Poland, 488 pp.

Marceau, M. L., and VanGeem, M. G., 2007, “Solar Reflectance of Concrete for LEED Sustainable Site Credit: Heat Island Effect,” SN2982, Portland Cement Association, Skokie, IL, pp. 3-18.

Mazria, E., 1979, The Passive Solar Energy Handbook, Rodale Press, pp. 5-65.

McCall, W. C., 1985, “Thermal Properties of Sandwich Panels,” Concrete International, V. 7, No. 1, Jan., pp. 35-41.

Mitalas, G. P., 1979, “Relation between Thermal Resistance and Heat Storage in Building Enclosures,” Building Research Note No. 126, Division of Building Research, National Research Council of Canada, Ottawa, ON, Canada, Jan.

National Concrete Masonry Association, 1989, “Heat Capacity (HC) Values for CEM Walls,” TEK 06-16, National Concrete Masonry Association, Herndon, VA.

National Concrete Masonry Association, 2008, “Heat Capacity (HC) Values for CM Walls,” TEK 06-16, National Concrete Masonry Association, Herndon VA.

National Concrete Masonry Association, 2010, “Thermal Catalog of Concrete Masonry Wall Assemblies,” TR 233, National Concrete Masonry Association, Herndon, VA.

Peavy, B. A.; Burch, D. M.; Powell, F. J.; and Hunt, C. M., 1972, “Comparison of Measured and Computer-Predicted Thermal Performance of a Four Bedroom Wood-Frame Townhouse,” Building Science Series 57, U.S. Department of Commerce, National Bureau of Standards, Washington, DC.





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http://dx.doi.org/10.15554/pcij.09011981.50.64

Peavy, B. A.; Powel, F. J.; and Burch, D. M., 1973, “Dynamic Thermal Performance of an Experimental Masonry Building,” Building Science Series 45, U.S. Department of Commerce, National Bureau of Standards, Washington, DC, July.

Petersen, P. H., 1949, “Burned Shale and Expanded Slag Concretes with and without Air-Entraining Admixture,” ACI Journal Proceedings, V. 45, No. 2, Oct., pp. 165-176.

Petersen, S. R.; Barnes, K. A.; and Peavy, B. A., 1981, “Determining Cost-Effective Insulation Levels for Masonry and Wood-Frame Walls in New-Single Family Housing,” Building Science Series 134, U.S. Department of Commerce, National Bureau of Standards, Washington, DC.

Petersen, S. R., and Barnett, J. P., 1980, “Expanded NBSLD Output for Analysis of Thermal Performance of Building Envelope Components,” U.S. Department of Commerce, National Bureau of Standards, Washington, DC.

Plonski, W., 1973a, “Thermal Conductivity and Moisture Content of Autoclaved Aerated Concrete,” Symposium on Lightweight Concrete, CEB Polish National Group/Engi-neering Committee, National Academy of Sciences, pp. 362-371.

Plonski, W., 1973b, “Thermal Conductivity and Moisture Content of Autoclaved Aerated Concrete,” Symposium on Lightweight Concrete, CEB Polish National Group/Engi-neering Committee, National Academy of Sciences, pp. 137-148.

Portland Cement Association, 1981, “Simplified Thermal Design of Building Envelopes,” Bulletin EBO89b, Portland Cement Association, Skokie, IL.

Portland Cement Association, 1982, “Effect of Building Mass on Thermal Loads of Multifamily Residences,” Bulletin CR62B, Portland Cement Association, Skokie, IL, Apr.

Price, W. H., and Cordon, W. A., 1949, “Tests of Light-weight-Aggregate Concrete Designed for Monolithic Construction,” ACI Journal Proceedings, V. 45, No. 8, Apr., pp. 581-600.

Robinson, G. C., 1980, Brick Walls for Passive Solar Use, Ceramic Engineering Department, Clemson University, Clemson, SC, Feb.

Rowley, F. B., and Algren, A. B., 1937, “Thermal Conduc-tivity of Building Materials,” Bulletin No. 12, Engineering Experiment Station, University of Minnesota, Minneapolis, MN, 134 pp.

Rudoy, W., and Dougall, R. S., 1979, “Effect of the Thermal Mass on the Heating and Cooling Loads in Resi-dences,” ASHRAE Transaction, V. 85, Part I, p. 903.

Spooner, D., 1977, Thermal Conductivity of Neat Portland Cement Paste, Cement & Concrete Association, Wexham Springs, UK.

Total Environment Action, Inc., 1980, Passive Solar Design Handbook, National Technical Information Service

(NTIS), Springfield, VA, V. 1, pp. A-13 through A-29, V. 2, pp. 72-76, 100.

Tye, R. P., and Spinney, S. C., 1976, Thermal Conductivity of Concrete: Measurement Problems and Effect of Moisture, Bulletin Annexe 76-2, Commission of BI of Institute Inter-national Du Froid, Paris, France, pp. 119-127.

Tyner, M., 1946, “Effect of Moisture on Thermal Conduc-tivity of Limerock Concrete,” ACI Journal Proceedings, V. 43, No. 1, Sept., pp. 9-18.

U.S. Department of Energy, 1989, “Energy Conservation Voluntary Performance Standards for New Commercial and Multi-Family High-Rise, Residential Buildings: Mandatory for New Federal Buildings,” 10 CFR, Part 435, Subpart A, Washington, DC.

U.S. Department of Energy, 2009, Commercial Building Tax Deductions Software, DOE2.2, Washington, DC.

U.S. Department of Energy, 2010, “EnergyPlus,” Building Technologies Simulation Program, Washington, DC.

Valore Jr., R. C., 1958, “Insulating Concretes,” ACI Journal Proceedings, V. 53, No. 5, May, pp. 509-535.

Valore Jr., R. C., 1980, “Calculation of U-Values of Hollow Concrete Masonry,” Concrete International, V. 2, No. 2, Feb., pp. 40-63.

Valore Jr., R. C., 1988, The Thermophysical Properties of Masonry and Its Constituents, International Masonry Insti-tute, Washington, DC.

Valore Jr., R. C., and Green, W. C., 1951, “Air Replaces Sand in ‘No-Fines’ Concrete,” ACI Journal Proceedings, V. 47, No. 10, June, pp. 833-846.

VanGeem, M. G., 1984, “Calibrated Hot Box Test Results Data Manual—Volume I,” Report No. ORNL/Sub/79-42539/4, Oak Ridge National Laboratory, U. S. Department of Energy, Nov., 336 pp.

VanGeem, M. G., 1986a, “Summary of Calibrated Hot Box Test Results for 21 Wall Assemblies,” ASHRAE Trans-actions, V. 92, Pt. 2, ASHRAE, Ann Arbor, MI.

VanGeem, M. G., 1986b, “Thermal Performance of Building Components,” ASHRAE Technical Data Bulletin TDB-84, ASHRAE, Ann Arbor, MI.

VanGeem, M. G., and Fiorato, A. E., 1983, “Thermal Prop-erties of Masonry Materials for Passive Solar Design—A State-of-the-Art Review,” Construction Technology Labora-tories, Portland Cement Association, Skokie, IL, Apr., 86 pp.

VanGeem, M. G., and Larson, S. C., 1984, “Calibrated Hot Box Test Results Data Manual—Volume II,” Report No. ORNL/Sub/79-42539/5, Construction Technology Labora-tories, Portland Cement Association, Skokie, IL, 164 pp.

Zoldners, N. G., 1971, “Thermal Properties of Concrete Under Sustained Elevated Temperatures,” Temperature and Concrete, SP-25, American Concrete Institute, Farmington Hills, MI, pp. 1-31.





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Table A.1a—Comparison of calculated and ASTM C236 U-values for concrete masonry walls with cores empty and filled, in Btu/(h·ft2·°F) (in.-lb units)

Wall no.Number of cores

Concrete masonry unit dimensions

Fractional web face

area

Aggregate

Concrete Core fill

U-value, Btu·(h·ft2·°F)Cores empty Cores filled

Calculation method

Test

Calculation method

TestLb, in. fs, in. aw ρ, lb/ft3 kc Type kf

Parallel path

Series- parallel

Parallel path

Series-parallel

PS-1 2 5.625 2.38 0.22 Lightweight 85 3.28 Perlite 0.45 0.391 0.395 0.36 0.174 0.212 0.20PS-2 2 7.625 3.04 0.22 Lightweight 82 3.09 Perlite 0.45 0.344 0.347 0.33 0.131 0.159 0.15PS-3 2 11.625 3.46 0.27 Lightweight 80 2.97 Perlite 0.45 0.301 0.314 0.29 0.093 0.108 0.10

PS-4 2 7.625 3.04 0.22Expanded

slag90 2.90 Perlite 0.45 — — — 0.128 0.153 0.152

PS-5 2 11.625 3.46 0.27Expanded

slag90 2.90 Perlite 0.45 — — — 0.092 0.107 0.113

PS-6 2 7.625 3.04 0.22 Limestone 138 9.48 Perlite 0.45 — — — 0.201 0.326 0.341PS-7 2 11.625 3.46 0.27 Limestone 139 9.48 Perlite 0.45 — — — 0.167 0.246 0.221PS-8 3 5.625 2.38 0.29 Lightweight 87 3.42 Vermiculite 0.60 0.398 0.399 0.40 0.218 0.261 0.26PS-9 2 7.625 3.04 0.22 Lightweight 85 3.28 Vermiculite 0.60 0.353 0.355 0.33 0.152 0.178 0.17PS-10 3 11.625 3.46 0.36 Lightweight 82 3.09 Vermiculite 0.60 0.296 0.310 0.30 0.119 0.135 0.15PS-11 2 7.625 3.04 0.22 Lightweight 126 7.46 Vermiculite 0.60 0.468 0.472 0.53 0.20 0.291 0.36

PS-12 3 3.625 2.36 0.29Expanded

shale76 2.74

Expanded shale

1.2 0.398 0.409 0.43 0.390 0.403 0.42

PS-13 2 7.625 3.04 0.22Expanded

shale77 2.80

Expanded shale

1.2 0.330 0.333 0.30 0.197 0.204 0.21

PS-14 2 11.625 3.46 0.27Expanded

shale71 2.48

Expanded shale

1.2 0.275 0.290 0.30 0.129 0.133 0.16

PCA-1 3 7.625 3.00 0.38Expanded

shale84 3.22

Expanded shale

1.2 0.343 0.346 0.36 0.228 0.242 0.24

PCA-2 3 7.625 3.00 0.38Expanded

shale84 3.22 Vermiculite 0.60 0.343 0.346 0.34 0.183 0.214 0.21

PCA-3 3 7.625 3.00 0.38Sand-light-

weight97 4.18 Vermiculite 0.60 0.386 0.387 0.39 0.209 0.251 0.24

PCA-4 3 7.625 3.00 0.38 Sand-gravel 136 9.11 Vermiculite 0.60 0.514 0.527 0.55 0.296 0.421 0.45UM-1 b,c 3 7.88 3.17 0.32 Cinders 86 3.35 Cork 0.35 0.346 0.348 0.70 0.144 0.185 0.201UM-1 d 3 7.88 3.17 0.32 Cinders 86 3.35 Cinders 2.0 0.346 0.348 0.370 0.264 0.268 0.248UM-1 e 3 7.88 3.17 0.32 Cinders 86 3.35 Rock wool 0.35 0.346 0.348 0.370 0.144 0.185 0.211

UM-2 b.c 3 7.88 3.17 0.32Expanded

shale77 2.80 Cork 0.35 0.318 0.322 0.344 0.131 0.163 0.172

UM-3 b,c 3 7.88 3.17 0.32 Sand-gravel 126 7.46 Cork 0.35 0.471 0.476 0.509 0.214 0.325 0.379UM-4a 3 7.88 3.17 0.37 Limestone 134 8.75 — — 0.949 0.504 0.510 — — —

UM-5 a.b 3 11.88 3.71 0.37 Cinders 86 3.35 Cork 0.35 0.299 0.312 0.74 0.109 0.132 0.199UM-6a 3 11.84 3.71 0.37 Sand-gravel 125 7.31 — — 0.420 0.421 0.481 — — —UM-7a 3 4.17 2.02 0.34 Cinders 100 4.43 — — 0.489 0.493 0.599 — — —UM-8a* 3 4.17 2.02 0.34 Cinders 100 4.43 Rock wool 0.35 0.233 0.239 0.279 0.162 0.165† 0.176UM-8b‡ — 4.17 — — — — — — — — — — — — —UM-9b§ 2 7.78 2.06 0.39 Sand-gravel 135 8.93 — — 0.515 0.520 0.525 — — —UM-10a 3 6.00 2.10 0.37 Cinders 74 2.64 — — 0.366 0.368 0.424 — — —

UM-11a 3 7.85 3.17 0.32Air-cooled

slag126 5.97 — — 0.437 0.438 0.441 — — —

UM-15 a, b

3 11.75 3.17 0.37Expanded

shale77 2.80 Cork 0.35 0.274 0.289 0.342 0.096 0.114 0.148

NW-1 2 7.62 3.80 0.22 Pumice 72 2.53 Perlite 0.45 0.292 0.294 0.25 0.129 0.152 0.13*Cavity wall with 1 in. air space.†U-value is 0.171 when corrected for metal ties by Method 2.‡Cavity filled with rock wool.§Nominal size of unit 8 x 5 x 12 in.

Note: Based on Valore (1980). The designation of this test procedure used when these tests were conducted, ASTM C236, has been changed to ASTM C1363.

APPENDIX A—TEST RESULTS AND CALCULATED THERMAL CONDUCTANCE OF OVEN-DRIED CONCRETE MASONRY





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Table A.1b—Comparison of calculated and ASTM C236 U-values for concrete masonry walls with cores empty and filled, W/(m2·K) (SI units)

Wall no.Number of cores

Concrete masonry unit

dimensions

Frac-tional

web face area

Aggregate

Concrete Core fill

U-value, W/(m2·K)Cores empty Cores filled

Calculation method

Test

Calculation method

TestLb, mm fs, mm aw ρ, kg/m3 kc Type kf

Parallel path

Series- parallel

Parallel path

Series-parallel

PS-1 2 143 60.5 0.22 Lightweight 1360 0.473 Perlite 0.065 2.22 2.24 2.04 0.99 1.20 1.14PS-2 2 194 77.2 0.22 Lightweight 1310 0.446 Perlite 0.065 1.95 1.97 1.87 0.744 0.903 0.852PS-3 2 295 87.9 0.27 Lightweight 1280 0.428 Perlite 0.065 1.71 1.78 1.65 0.528 0.613 0.568

PS-4 2 194 77.2 0.22Expanded

slag1440 0.418 Perlite 0.065 — — — 0.727 0.869 0.863

PS-5 2 295 87.9 0.27Expanded

slag1440 0.418 Perlite 0.065 — — — 0.523 0.608 0.642

PS-6 2 194 77.2 0.22 Limestone 2210 1.37 Perlite 0.065 — — — 1.14 1.85 1.94PS-7 2 295 87.9 0.27 Limestone 2220 1.37 Perlite 0.065 — — — 0.949 1.40 1.26PS-8 3 143 60.5 0.29 Lightweight 1390 0.493 Vermiculite 0.087 2.26 2.27 2.27 1.24 1.48 1.48PS-9 2 194 77.2 0.22 Lightweight 1360 0.473 Vermiculite 0.087 2.01 2.02 1.87 0.863 1.01 0.97PS-10 3 295 87.9 0.36 Lightweight 1310 0.446 Vermiculite 0.087 1.68 1.76 1.70 0.676 0.767 0.852PS-11 2 194 77.2 0.22 Lightweight 2020 1.08 Vermiculite 0.087 2.66 2.68 3.01 1.14 1.65 2.04

PS-12 3 92.1 59.9 0.29Expanded

shale1220 0.395

Expanded shale

0.173 2.26 2.32 2.44 2.22 2.29 2.39

PS-13 2 194 77.2 0.22Expanded

shale1230 0.404

Expanded shale

0.173 1.87 1.89 1.70 1.12 1.16 1.19

PS-14 2 295 87.9 0.27Expanded

shale1140 0.358

Expanded shale

0.173 1.56 1.65 1.70 0.733 0.755 0.909

PCA-1 3 194 76.2 0.38Expanded

shale1340 0.464

Expanded shale

0.173 1.95 1.97 2.04 1.30 1.37 1.36

PCA-2 3 194 76.2 0.38Expanded

shale1340 0.464 Vermiculite 0.087 1.95 1.97 1.93 1.04 1.22 1.19

PCA-3 3 194 76.2 0.38Sand-light-

weight1550 0.603 Vermiculite 0.087 2.19 2.20 2.22 1.19 1.43 1.36

PCA-4 3 194 76.2 0.38 Sand-gravel 2180 1.31 Vermiculite 0.087 2.92 2.99 3.12 1.68 2.39 2.56UM-1

b,c3 200 80.5 0.32 Cinders 1380 0.483 Cork 0.050 1.97 1.98 3.98 0.818 1.05 1.14

UM-1 d 3 200 80.5 0.32 Cinders 1380 0.483 Cinders 0.288 1.97 1.98 2.10 1.50 1.52 1.41UM-1 e 3 200 80.5 0.32 Cinders 1380 0.483 Rock wool 0.050 1.97 1.98 2.10 0.82 1.05 1.20UM-2

b.c3 200 80.5 0.32

Expanded Shale

1230 0.404 Cork 0.050 1.81 1.83 1.95 0.744 0.926 0.977

UM-3 b,c

3 200 80.5 0.32 Sand-gravel 2020 1.076 Cork 0.050 2.68 2.70 2.89 1.22 1.85 2.15

UM-4a 3 200 80.5 0.37 Limestone 2140 1.26 — — 5.39 2.86 2.90 — — —UM-5

a.b3 302 94.2 0.37 Cinders 1380 0.483 Cork 0.050 1.70 1.77 4.20 0.619 0.750 1.13

UM-6a 3 301 94.2 0.37 Sand-gravel 2000 1.05 — — 2.39 2.39 2.73 — — —UM-7a 3 106 51.3 0.34 Cinders 1600 0.639 — — 2.78 2.80 3.40 — — —

UM-8a* 3 105 51.3 0.34 Cinders 1600 0.639 Rock wool 0.050 1.32 1.36 1.58 0.920 —† 1.00UM-8b‡ — 106 — — — — — — — — — — — — —UM-9b§ 2 198 52.3 0.39 Sand-gravel 2160 1.29 — — 2.93 2.95 2.98 — — —UM-10a 3 152 53.3 0.37 Cinders 1180 0.381 — — 2.08 2.09 2.41 — — —

UM-11a 3 199 80.5 0.32Air-cooled

slag2020 0.861 — — 2.48 2.49 2.50 — — —

UM-15 a, b

3 298 80.5 0.37Expanded

shale1230 0.404 Cork 0.050 1.56 1.64 1.94 0.545 0.648 0.841

NW-1 2 194 96.5 0.22 Pumice 1150 0.365 Perlite 0.065 1.66 1.67 1.42 0.733 0.863 0.738*Cavity wall with 25.4 mm air space.†U-value is 0.971 when corrected for metal ties by Method 2.‡Cavity filled with rock wool.§Size of unit 203 x 127 x 305 mm.

Notes: Based on Valore (1980).The designation of this test procedure used when these tests were conducted, ASTM C236, has been changed to ASTM C1363.





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Table A.2a—Comparison of calculated and ASTM C236 U-values for concrete masonry walls with cores empty and filled, Btu/(h·ft2·°F) (in.-lb units)

Wall no.

Number of cores

Concrete masonry

dimensions

Frac-tional

web face area

Aggregate

Concrete Core fill

U-value, Btu / (h·ft2·°F)Cores empty Cores filled

Calculation method

Test

Calculation method

TestLb, in. fs, in. aw ρ, lb/ft3 kc Type kf

Parallel path

Series parallel

Parallel path

Series parallel

D-2 2 5.625 2.38 0.22 Sand-gravel 131 8.31 — — 0.514 0.535 0.58 — — —D-4 2 7.625 3.04 0.22 Sand-gravel 132 8.41 — — 0.483 0.490 0.56 — — —D-4 2 11.625 3.46 0.27 Sand-gravel 135 8.93 — — 0.456 0.456 0.48 — — —D-7 2 7.625 3.04 0.22 Pumice 62 2.07 — — 0.286 0.292 0.33 — — —

D-10 2 11.625 3.46 0.27 Sand-light-weight 95 4.01 — — 0.347 0.354 0.35 — — —

D-11 2 7.625 3.04 0.22 Sand-light-weight 95 4.01 — — 0.383 0.383 0.42 — — —

D-21 2 7.625 3.04 0.22 Fly ash 80 2.97 — — 0.339 0.341 0.36 — — —D-38* 2 7.625 3.04 0.22 Fly ash 80 2.97 — — 0.333 0.335 0.33 — — —D-24,

25 3 5.625 2.38 0.29 Sand-light-weight 98 4.26 Perlite 0.45 0.432 0.433 0.42 0.219 0.286 0.30

D-UF1† 2 7.625 3.04 0.22 Sand-light-weight 105 4.90

Urea formalde-hyde foam

0.30 — — — 0.138 0.201 0.24

D-UF2† 2 7.625 3.04 0.22 Sand-gravel 133 8.58Urea

formalde-hyde foam

0.30 — — — 0.174 0.297 0.30

D-UF3‡ 2 11.625 3.46 0.27 Sand-light-weight 113 5.75

Urea formalde-hyde foam

0.30 — — — 0.119 0.165 0.18

D-UF4† 2 11.625 3.46 0.27 Sand-gravel 133 8.58Urea

formalde-hyde foam

0.30 — — — 0.148 0.224 0.23

D-UF5† 2 11.625 3.46 0.27 Lightweight 91 3.70Urea

formalde-hyde foam

0.30 — — — 0.093 0.118 0.12

RI-1 2 7.625 3.04 0.22 Sand-gravel 140 9.87 — — 0.503 0.517 0.508 — — —RI-2 2 7.625 3.04 0.22 Lightweight 101 4.52 — — 0.400 0.400 0.381 — — —

*Fibered surface-bonded cement plaster on both sides.†Urea-formaldehyde insulation foamed in place at cores.

Notes: Based on Valore (1980). The designation of this test procedure used when these tests were conducted, ASTM C236, has been changed to ASTM C1363.





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Table A.2b—Comparison of calculated and ASTM C236 U-values for concrete masonry walls with cores empty and filled, W/(m2·K) (SI units)

Wall no.

Number of cores

Concrete masonry

dimensions

Frac-tional

web face area

Aggregate

Concrete Core fill

U-value, W/(m2·K)Cores empty Cores filled

Calculation method

Test

Calculation method

TestLb, mm

fs, mm aw ρ, kg/m3 kc Type kf

Parallel path

Series parallel

Parallel path

Series parallel

D-2 2 143 60.5 0.22 Sand-gravel 2100 1.20 — — 2.92 3.04 3.29 — — —D-4 2 194 77.2 0.22 Sand-gravel 211 1.21 — — 2.74 2.78 3.18 — — —D-4 2 295 87.9 0.27 Sand-gravel 2160 1.29 — — 2.59 2.59 2.73 — — —D-7 2 194 77.2 0.22 Pumice 990 0.298 — — 1.62 1.66 1.87 — — —

D-10 2 295 87.9 0.27 Sand-light-weight 1520 0.578 — — 1.97 2.01 1.99 — — —

D-11 2 194 77.2 0.22 Sand-light-weight 1520 0.578 — — 2.18 2.18 2.39 — — —

D-21 2 194 77.2 0.22 Fly ash 1280 0.428 — — 1.93 1.94 2.04 — — —D-38* 2 194 77.2 0.22 Fly ash 1280 0.428 — — 1.89 1.90 1.87 — — —D-24,

25 3 143 60.5 0.29 Sand-light-weight 1570 0.614 Perlite. 0.065 2.45 2.46 2.39 1.24 1.62 1.70

D-UF1† 2 194 77.2 0.22 Sand-light-weight 1680 0.707

Urea formalde-hyde-foam

0.043 — — — 0.784 1.14 1.36

D-UF2† 2 194 77.2 0.22 Sand-gravel 2130 1.24Urea

formalde-hyde-foam

0.043 — — — 0.988 1.69 1.70

D-UF3† 2 295 87.9 0.27 Sand-light-weight 1810 0.829

Urea formalde-hyde-foam

0.043 — — — 0.676 0.937 1.02

D-UF4† 2 295 87.9 0.27 Sand-gravel 2130 1.24Urea

formalde-hyde-foam

0.043 — — — 0.841 1.27 1.31

D-UF5† 2 295 87.9 0.27 Lightweight 1460 0.534Urea

formalde-hyde-foam

0.043 — — — 0.528 0.670 0.682

RI-1 2 194 77.2 0.22 Sand-gravel 2240 1.42 — — 2.86 2.94 2.89 — — —RI-2 2 194 77.2 0.22 Lightweight 1620 0.652 — — 2.27 2.27 2.16 — — —

*Fibered surface-bonded cement plaster on both sides.†Urea-formaldehyde insulation foamed in place at cores.

Notes: Based on Valore (1980). The designation of this test procedure used when these tests were conducted, ASTM C236, has been changed to ASTM C1363.





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Documents

ACI 122R-14: Guide to Thermal Properties of Concrete and ... · This guide reports data on the thermal properties of concrete and masonry constituents, masonry units, and systems