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Electric infrared heating panels vs. HVAC, © 2015, 2016 Oswald Oberladstatter Page 1

Electric Infrared Heating Panels

vs. HVAC

- a summary of an U.S. study (1994)

a project report made by

Perl, Germany

October 2016


Project report title:

Electric Infrared Heating Panels vs. HVAC

- a summary of an U.S. experimental field study (1994)

Author:

Oswald Oberladstatter, ME

ehaus2020, Perl, Germany

The author has 15+ years of experience working as HVAC-engineer

and project manager for European companies. Since 2011, he engages

in systems-design for "affordable, healthy Net-Zero-Energy-Buildings".

From 2012 until 2015, he organized four European electric infrared

heating industry alliances, and was an expert-member of a German

Standard committee on an European performance testing standard for

electric infrared panels.

Perl, Germany

edition: October 2016

© copyright 2016 by the author

correspondence about this project report should be directed to [email protected]


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Content

1. Abstract ................................................................................. page 6

2. The U.S. study ........................................................................ page 6

3. Facts regarding the three electric heating systems used ........ page 7

4. The research house ................................................................ page 8

5. Heat transfer through walls and windows............................... page 8

6. Heat loss through natural air-infiltration................................. page 9

7. Installed heating system capacity .......................................... page 10

8. Installation of the electric infrared heating system ................ page 10

9. Thermal comfort results ......................................................... page 12

10. Results of energy consumption and operating costs ............... page 15

11. Conclusion .............................................................................. page 16

12. Appendix: 3 major factors ...................................................... page 17

13. Bibliography ........................................................................... page 18


Electric Infrared Heating Panels vs. HVAC

- a summary of an U.S. experimental field study (1994)

Author: Mr. Oswald Oberladstatter, ME, ehaus2020, Perl, Germany

Date: April 2015

1 Abstract

Some of the main arguments against surface-mounted electric infrared heating systems

center on the preconceived notions that "all-electric heating is always expensive" and "heat

rises, so placing heating panels up on a wall or on the ceiling makes no sense".

Therefore, the focus of an U.S. study was to compare the thermal comfort, operational

costs and energy consumption in an occupied residential research house for a common air-

to-air heat pump system (HVAC) and a ceiling-mounted electric infrared heating system.

Further, energy consumption was compared to an electric baseboard heating system,

previously installed in the same house.

The U.S. study outcome points towards the fact, that it is more energy-efficient

and thermally more comfortable to heat room-surfaces with surface-mounted

electric infrared heating panels, than by heating the air with an HVAC-system.

2 The U.S. study

Owing to current building standards, European new construction and renovation projects

are highly insulated and air-tight.

In a different direction points a 20+ year old U.S. study /1/. This study provides proof,

that buildings can be energy-efficient and feel comfortably warm inside without extensive

insulation measures, and without an expensive "air-tight thermos bottle" construction.

The study was conducted in 1994 by the National Association of Home Builders (NAHB)

Research Center, a research platform for the U.S. construction industry.

The U.S. Department of Energy as well as the U.S. based company SSHC INC., a

manufacturer of surface-mounted electric infrared heating panels, jointly financed the

research study.


The study's main research objectives were:

to use an occupied research house for one-half of the 1993-1994 heating season;

utilizing a data monitoring system to determine the energy-efficiency and

operational costs of surface-mounted electric infrared heaters and an air-to-air

heat pump HVAC-system; operate both systems alternately in 2-week blocks when

possible, otherwise in 1-week blocks;

use data from a previously in the house installed electric baseboard heating

system;

balancing varying weather influences by using a regression analysis of outdoor

temperature and energy consumption, weighted by local weather data.

get feed-back from house occupants regarding thermally discomfortable conditions.

3 Facts regarding the three electric heating systems used

Picture-1 to the left shows a surface-mounted electric infrared

heating panel as used in the study. Panels were each sized

between 0,6 x 0,6 meters to 0,6 x 2,4 meters, featuring a

textured surface coating and an aluminum frame with a 1"

profile. Inside each panel is a solid-state electric heating

element. Even though the regular power supply in U.S.

households is 120V, each panel was connected to 240V. Also

out of the ordinary were hydraulic line thermostats installed

room-by-room. Their advantage was a high accuracy in

picture-1, ©SSHC INC. monitoring the air- and radiant temperatures in the rooms.

Pertaining to the HVAC-system, notable facts are that there were two heat-pump units

installed in the attic, one for the first floor and one for the second floor. The total installed

capacity of the two units was 12 kW. However, since the primary heat source during winter

design conditions is the backup strip-heater with 15 kW of electric power, the total HVAC

capacity under design conditions was 16,7 kW. Very unusual for the 1990's, programmable

thermostats with a "predictive" mode were used, one each installed in the hallways in the

lower and upper floors. This allowed for efficient HVAC operation with setback strategies.

In regards to the electric baseboard system, there are several factors that need to be

mentioned. The installed power for this system was oversized by +54% compared to the

Right-J calculation for the design load of the building. This was standard practice to

anticipate for the day and night setback strategies /2/. This setback strategy in

conjunction with room-by-room thermostatic controls was used in the not-occupied house

to simulate occupancy. Also, the actual indoor temperature was about 1,1°C higher as

compared to the surface-mounted infrared heating system and the HVAC-system.


4 The research house

Picture-2 below shows the now disassembled research house which was a fairly typical

American contemporary detached home. It was located on the grounds of the NAHB

Research Center in Bowie, Maryland, close to Washington D.C. on the U.S. East Coast.

picture-2: the AFSD House, © by Jane Willeboordse, Popular Science, Sept. 1990

The house was built in 1990 as a 2-story single-family home with ca. 205 square meters of

floor space and an attached garage. Because of its modular construction, sprinkler system,

etc., the house was called the "Adaptable Fire-Safe Demonstration House" (AFSD House).

5 Heat transfer through walls and windows

Exterior walls were made with a common "2x4" wood frame construction with 2,45 meter

ceiling heights, painted gypsum board on the interior, wood or vinyl siding on the exterior,

and 0,10 meter thick fiberglass insulation batts inside the wood-frame walls.

Casement windows used in the AFSD House consisted of wooden sashes with double

glazing and a crank operator. Typical for U.S.-buildings in the 1990's, the window glass

had no low-e coating and no energy saving inert-gas in the glazing cavity.

The heat transfer value, called "U-value", based on the international Standard ISO 6946

for the wall construction is 0,31 W/m2∙K /3/. The U-value for the windows is estimated

with 2,55 W/m2∙K /4/.


In comparison:

The minimum U-values as per the German building code "EnEV2014" for exterior walls are

0,24 W/m2∙K, and for windows 1,30 W/m2∙K /5/. Thereby, U-values of the AFSD House

are considerably higher than the German building code.

However, winter design conditions with an outdoor air temperature lower than -10,5°C in

97,5% of all measurement intervals, make the winter climate conditions of the AFSD

House study comparable to Middle-European locations.

6 Heat loss through natural air-infiltration

Displacement of warm interior air by colder outside air through tiny gaps in the building

envelope is called natural air-infiltration. This is another primary parameter of heat loss in

buildings and closely related to construction materials and methods.

The basic principle:

The higher the natural air-infiltration rate, the higher the heat loss

of the building.

To determine the natural air-infiltration of the AFSD House, a "blower-door test" in

accordance with the ASTM Standard /6/ was performed prior to the start of the research

project. With the air-ducts sealed, as would be the case with infrared heating, the natural

air-infiltration rate for the house was 0,88 per hour. With the air-ducts open, as in the case

for HVAC heating, the air-infiltration rate was 0,99 per hour.

With the air-ducts open, this resulted in a 12,5% higher natural infiltration rate than with

air-ducts sealed. U.S. research indicates, that forced-air heating systems may have an up

to 36% higher natural air-infiltration rate /7/.

A natural air-infiltration rate of 0,88 per hour, as with electric infrared heating in operation,

places the AFSD House in the U.S. "average" category of 0,7 to 0,88 per hour /8/.

In comparison:

A recent Austrian blower-door study /9/ in 3 old and new residences measured air change

rates of 4,8 to 8,3 per hour at 50 pascal pressure differential.

Dividing these rates by 16 /10/results in a natural air-infiltration rate of 0,3 to 0,52 per

hour, averaging 0,4 per hour.

This indicates, that the natural air-infiltration rate of the AFSD House with 0,88 is more

than double that of typical Austrian residences with a 0,4 infiltration rate.


7 Installed heating system capacity

For benchmarking purposes, the common U.S. Right-J m method was used to calculate the

building heat load /11/.

Table-1 Right-J

building heat loss calculation

electric

baseboard HVAC

surface-mounted infrared panels

indoor air temp.

outdoor air temp.

21,1 °C

- 10,5 °C

21,1 °C

- 10,5 °C

21,1 °C

- 10,5 °C

18,3 °C

- 12,2 °C

assumed natural

air-infiltration 0,7 0,7 -- 0,4

setback strategies

anticipated no yes yes yes

heating system's

installed capacity 13,3 kW 20,5 kW 16,7 kW 8,1 kW

comparison

100% +54% +26% - 40%

Explanation about table-1:

According to the AFSD House study, almost all of the 40% reduction in installed heating

capacity vs. the Right-J calculation originates from using 0,4 as natural air-infiltration rate.

That is 43% less than the 0,7 assumed rate by the standard Right-J method, and about

55% less than the actual 0,88 natural air-infiltration rate of the AFSD House, but equals

the average natural air-infiltration rate of the Austrian study mentioned above. Different

indoor/outdoor design temperatures accounted only for ca. 4% of the difference in the

calculation results, whereas thermostat setback strategies had no influence.

The AFSD House study results confirmed, that the electric infrared panel

manufacturer's heat loss calculation was correct, providing sufficient thermal

comfort even in cases below winter design conditions.

In comparison: The 40% reduction in installed heating capacity of the surface-mounted

infrared heating panels in the AFSD House compares well to current Middle-European data.

A German study /12/, building project presentations at a German Workshop /13/, and

results from a 1950's German residence /14/, all point to the same fact: a 30% to 60%

reduction in installed heating capacity vs. accepted building standard calculations provide

sufficient thermal comfort to occupants under winter design conditions. However, this does

not apply to buildings with high moisture content in their construction materials, i.e. new

buildings made of regular concrete, or buildings with moisture problems (mold, mildew).

8 Installation of the electric infrared heating system

Picture-3 and -4 on the next page display the floor plans of the AFSD House with the

locations of the ceiling-mounted electric infrared heating panels.


picture-3: AFSD House 1st floor, © 2015, 2016 Oswald Oberladstatter

family room bathroom 7,3m2 kitchen

22,11m2 9,05m2

dining room

15,28m2

garage

den / bedroom foyer living room

16,52m2 15,65m2

location of ceiling-mounted electric infrared heating panels

The AFSD House had 205 square

meters of living space and 16 ceiling- picture-4: AFSD House 2nd floor,

mounted electric infrared heating © 2015, 2016 Oswald Oberladstatter

panels with a total heating capacity

of 8100 Watt. This results in an

installed heating capacity of bathroom bathroom bedroom

39,5 Watt per square meter of 6,99m2 6,50m2 11,18m2

living space. Surface temperature

of the infrared heating panels during

operation was between 65,5°C and

ca. 76,5°C. 9,18 square meters of

infrared panel surface was installed

on the first floor, 6,48 square meters master

on the second floor. In total, panel bedroom

surface was 15,66 square meters, 16,52m2 (open) bedroom

equating to infrared heating panel 15,65m2

surface of 8% of the living space

area.

Note: the study mentioned, that for

the 22,11 square meters large family room, the 2,23 square meters of installed infrared

heating panel surface (10% of family room floor space) was probably too little. The likely

reason for that: the room with its 5 exterior room surfaces (3 walls, ceiling, floor), had

more heat loss than the average room with only 2 to 3 exterior room surfaces. The

thermostats setback air temperature was 15,5°C. The AFSD House study also mentions,

that the setforward air temperature of 20°C was probably at the lower margin of

thermal comfort for both house occupants.


9 Thermal comfort results

The "operative temperature" is a useful parameter in assessing the thermal comfort of

house occupants. To derive the median operative temperature in a room, globe-sensors

measured the mean radiant temperature and the ambient air temperature in a room.

Based on scientific studies, the following describes the ideal range for the operating

temperature.

During winter conditions, if the operative temperature stays

within 20°C to 24°C in a room, about 90% of room occupants

may feel thermally comfortable /16/.

In the AFSD House, three globe-sensors were located in three different locations to

continuously monitor the operating temperature during the operation of the HVAC- and

surface-mounted infrared heating panels.

The AFSD House was occupied by a working couple. The female house occupant submitted

four times as many thermal discomfort claims as the male occupant. This supports the

notion that women are in general more sensitive to changes in thermal comfort than men.

However, quick changes in temperature seem to have the same effect on women and men.

One such case is "infrared panel cycling" as depicted in picture-5 below.

picture-5: infrared panel cycling and thermal comfort, © 2015, 2016 Oswald Oberladstatter


Picture-5 on the previous page displays a sharp drop of the operative temperature within a

20 minute period from about 23°C to 21°C. This was caused by the infrared heating panel

cutting off at 13:35pm and cutting back on again at 13:55pm ("infrared panel cycling").

At that time, occupants were sitting in the dining room right beneath a ceiling-mounted

infrared heating panel. During this "infrared panel cycling", occupants experienced

occasionally thermal discomfort.

Interestingly, at the same time two other occupants in the room who were not located

right beneath the infrared heating panel, did not register thermal discomfort.

Thermal comfort recommendations from the AFSD House study:

In regards to thermal comfort with surface-mounted infrared heating panels,

there is a difference between "rooms" and "open spaces". In connected open

spaces like the area of the dining and living room in the AFSD House, it is better

to connect all infrared heating panels located in this open space to one thermostat,

in order to avoid thermal discomfort for moving-around occupants.

For thermal comfort reasons, the study also suggests that "the square area of

panels installed should be held constant while increasing the number of panels".

In other words: It is better to use more infrared heating panels that are

smaller in size, than just one big panel per room or open space.

In the experience of the author, with surface-mounted electric infrared heating panels keep

the thermostat's setback air temperature at least at 18°C. Contrary to popular belief, in

general this saves energy for heating-up all room surfaces every morning. It also reduces

heat-up time, and therefore improves occupants' thermal comfort.

Furthermore, the AFSD House study noted, that with the surface-mounted infrared heating

panels in operation and occupants having substantial skin surface exposed, the occupants

mentioned on occasion that walking from room to room felt rather cool.

However, AFSD House occupants also felt that acceptable thermal conditions could be

achieved in approximately 10 to 15 minutes if activity was restricted to the proximity of

the surface-mounted infrared heating panels. Establishing thermal comfort in the entire

room required approximately 45 minutes.

This corresponds well with research data from the Pierce Foundation /15/, showing that

occupants of an infrared heated enclosure accept cool spaces upon entry as long as the

infrared heating system can raise the operative temperature within 15 minutes to

acceptable levels.


Typical air- and operative temperatures in the dining room of the AFSD House, with winter

outdoor air temperature at around -2,2°C are shown in picture-6 below.

picture-6: typical air- and operative temperatures, © 2015, 2016 Oswald Oberladstatter

In picture-6, the air- and operative temperatures of the HVAC-system are almost the same

and largely between 19°C to 20°C. For the surface-mounted infrared heating system, the

air temperature is ca. 18°C, and the operative temperature ranges from 21,5°C to about

22°C. The operative temperature remains therefore within the previously recommended

operative temperature range of 20°C to 24°C.

These monitoring results confirm a simple fact: Because heat does NOT rise (only

hot air does), it DOES make sense to locate surface-mounted infrared heating

panels up on a wall or on the ceiling.

Even before knowing of its superior energy-efficiency over the HVAC-system, occupants

preferred the surface-mounted infrared heating panels for the following comfort reasons:

occupants had greater control over the heating system on a room-by-room basis,

and therefore more control over their specific thermal comfort requirements;

silent operation of the surface-mounted infrared heating system as there is no air

movement and no fan noise as with the HVAC-system;

occupants had fewer problems with sinus discomfort, especially during the night.


10 Results of energy consumption and operating costs

Chart-1 and -2: comparative energy- and cost levels, © Oswald Oberladstatter

Summary of the charts-1 and -2 above:

In regards to the electric infrared heating panels, heating energy consumption was

35,3 kWh per square meter and heating season.

In other words: In the same AFSD House, the surface-mounted electric infrared

heating panels cost about 33% less to operate than the HVAC-system, and 52%

less than electric baseboard heating.

This also refutes the notion that "all-electric heating is always expensive".

The AFSD House study contributes the energy savings from the surface-mounted electric

infrared heating panels to the compounded effect of

reduced parasitic heat losses,

room zoning,

quick recovery from setback, and

heating for comfort.


In comparison:

Costs in the chart-2 above are based on the AFSD House study with an electricity price of

$0,055/kWh in 1994 (the currency conversion factor in April 2015 was $1 = €0,88).

For 2015: The residential electricity retail price in March 2015 in Maryland/USA was

$0,1316/kWh (€0,1158/kWh) /17/. The resulting operational costs in 2015 over a heating

season for the surface-mounted infrared heating panels would be $951 (€837), for the

HVAC-system $1.417 (€1.247) and $1.988 (€1.749) for electric baseboard heating.

Pertaining energy-efficiency and sizing of heating systems:

In the professional experience of the author, oversizing a convection-based heating system

by 50% usually leads to very poor energy-efficiency results. This might had been the case

with the electric baseboard heating system which was used for comparison in the AFSD

House study.

The same study also points out, that the undersized surface-mounted electric infrared

heating panels in the family room resulted in occasional thermal discomfort (note by the

author: and probably also poor energy-efficiency, because infrared heating panels are then

almost constantly in operation).

11 Conclusion

The exterior walls and windows of the AFSD House had much higher heat transfer values

and double the natural air-infiltration rate compared to current European building codes.

Despite these facts, the installed surface-mounted electric infrared heating system

enables a superior energy-efficiency and operational cost-efficiency over common

HVAC- and electric baseboard heating systems,

was preferred by the AFSD House occupants for its comfort, convenience and health

features over the air-to-air heat pump HVAC-system,

allows for a 40% reduced heat load capacity as compared to the standard Right-J

heating and cooling load calculation method, and about a 50% reduction based on

the measured natural air-infiltration rate of 0,88 per hour.

The AFSD House study indicates, that energy-efficient and thermally comfortable homes

can be built without ridiculous amounts of insulation and expensive air-tightness

requirements, by using electric surface-mounted infrared panels.


12 Appendix: 3 major factors

In the experience of the author, the combination of 3 major factors determines the

energy-efficiency and operations costs for surface-mounted infrared heaters in

residential settings:

1. occupants wants and needs,

2. an understanding on how an infrared heating system really works, and

3. the importance of building materials that match infrared heater characteristics.

Many topics of the 1st factor are well documented in the AFSD House study.

As for the 2nd factor:

The following explains how surface-mounted electric infrared heating panels as main

heating system achieve superior energy-efficiency and thermal comfort in residential

settings:

Surface-mounted electric infrared heating panels work by minimizing

the infrared-heat exchange between humans and room surfaces. Hence,

their main purpose is to elevate the temperatures of all room surfaces.

As an effect, room air temperature can be lower to achieve satisfactory

thermal comfort for occupants.

Pertaining to the 3rd factor:

The thermal characteristics of the interior top-layers of walls, ceilings and floors as well as

furniture surfaces need to be such, as to enable them to act as "re-radiant heaters".

In this regard, there are three basic physical parameters for surface materials:

1. High thermal emissivity of greater than 0,8 in the thermal spectral range

of 2,5 to 50 micrometers, which defines a material's ability to emit infrared

heat. This can be measured with an FTIR-spectrometer;

2. Low thermal effusivity, ideally below 30 kJ/m2∙K, which expresses a

material's capacity about the speed to absorb heat and store it. Effusivity

can be measured by using i.e. a hot disk single-sided sensor device.

3. Fast temperature spread along the surface layer of the material, or as the

author calls it, "blotting-paper effect" (in German: "Löschblatt-Effekt"),

which is important for radiant heat symmetry in rooms. This material

property can be observed by utilizing a suitable infrared camera.


13 Bibliography

/1/ Yost, Barbour, Watson for NAHB Research Center, 400 Prince George's Boulevard,

Upper Malboro, MD 20772, U.S.A: An Evaluation of Thermal Comfort and Energy

Consumption for the Enerjoy Radiant Panel Heating System; May 31st 1994

/2/ ASHRAE, 1993 ASHRAE Handbook: Fundamentals, 1993, pp. 25 - 14

/3/ Oswald Oberladstatter, U-value calculation with "U-Therm" software from

German software company Hottgenroth, based on AFSD House wall-construction

/4/ Kennwerte-Fenster (U-values of wood frame windows with double glazing),

page 1, table 1 - Doppelverglasung / Holz-/Kunststoffrahmen, TWW

www.energieberaterkurs.de/export/sites/default/de/Dateien_Kennwerte/

kennwerte_fenster.pdf window U-value

/5/ Minimum U-values as per the current German building Standard EnEV2014

www.enev-online.com/enev_2014_volltext/anlage_03_anforderungen _aenderung

_aU.S.senbauteile _bestand.htm#Anlage 3_Nr_7._Tabelle_Anforderungen

/6/ ASTM Standard E779-87: Method for Determining Air Leakage by Fan

Pressurization

/7/ Palmiter, L. S., I. A. Brown, and T. C. Bond, "Measured Infiltration and

Ventilation in 472 All-electric Homes", ASHRAE Transactions, 91.15.3

/8/ Goldschmidt, V. W. "Average Infiltration Rates in Residences: Comparison of

Electric and Combustion Heating Systems", Measured Air Leakage of Buildings,

ASTM STP 904, H. R. Trechsel and P. L. Lagus, Eds., ASTM, Philadelphia, 1986,

pp. 70-98

/9/ Peter Tappler, Bernhard Damberger, Felix Twdirk, Karl Mitterer, Hans-Peter

Hutter, "Pilotstudie zur Untersuchung des Luftwechsels in Innenräumen für die

Erarbeitung von Vorgaben der Publikation 'Richtlinie zur Bewertung der

Inneraumluft", Endbericht Dezember 2006

/10/ Persily, A. K. "Measurements of Air Infiltration and Airtightness in Passive Solar

Homes", Measured Air Leakage of Buildings, ASTM STP 904, H. R. Trechsler and

P. L. Lagus., Eds., ASTM, Philadelphia, 1986, pp. 46-60

/11/ The Right-J method is a standard design procedure for heating and cooling

systems in the U.S., and certified by the Associated Conditioning Contractors of

America (ACCA)

/12/ Peter Kosack, Report on the Research Project "Case Study of the Differences

between Infrared Heating and Gas Heating in an Old Residential Building, Using

Comparative Measurement", Arbeitskreis Ökologisches Bauen, Technical University

of Kaiserslautern, October 2009


/13/ Third International Workshop for Infrared Heaters, The correct application of

electric infrared heaters in residential buildings, Technical University of

Kasiserslautern, Germany, April 16th 2015

/14/ Dirk Pulver, electric infrared heaters - a practical point of view, Presentation at the

University of Liege, campus Arlon, Belgium, July 10th 2012

/15/ Berglund L., R. Rascati, and M. L. Markel, "Radiant Heating and Control for

Comfort During Transient Conditions", ASHRAE Transactions, Part 2: 765-775, 1982

/16/ L. Centnerova, J.L.M. Hensen, Energy and indoor temperature consequences of

adaptive thermal comfort standards, Proceedings of the 4th international conference

on indoor climate of buildings, pp. 391-402, Bratislava, 2001

/17/ Average residential retail price for electricity in the USA, March 2015

www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_6_a

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