12 Thermal Comfort GB 2009color

8/6/2019 12 Thermal Comfort GB 2009color

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Thermal Comfort

Arch 140, Lecture #12

Thursday, February 26, 2009


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ASHRAE*definition:that condition of mind which

expresses satisfaction with the

thermal environment

But thermal discomfort is

What is Thermal Comfort?

measure, as a result .

Engineers view:

Comfort= absence of discomfort

= neutrality

* American Society of Heating, Refrigerating, and Air-Conditioning Engineers


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Experiential goals

Thermal neutrality or Thermal delight ??


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Thermal comfort & architectural elements


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Thermal comfort & the workplace


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year

200 -

150 -

100 -~ 2 /ft2- r ~ 20 $/ft

2-yr

~ 200 $/ft2-yr

Over the life of a building, occupancy costs substantially

exceed both energy and financing costs

Energy Finance Occupants (salaries)

$/ft2

50 -

0 -


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Comfort & the Bodys Heat Balance


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Heat Gains & Losses

37 C = 98.6 F


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Influences our bodys thermoregulatory system

1. Blood flow- vasoconstriction

- vasodilation

Physiological Control Mechanisms - Involuntary

2. Sweating

3. Shivering

4. Goosebumps


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Environmental Personal

- Turning on/off fan - Changing clothing- Turning on/off heater - Changing activity

- O enin /closin : - Chan in osture

Behavioral Control Mechanisms - Voluntary

> windows position or location> blinds & shades - Eating/drinking

something cold or hot


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Measurable factors that influence the bodysheat balance


1. Air temperature 1. Activity

Major Variables Influencing Thermal Comfort

. um y . n3. Air velocity

4. Mean radiant temperature


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Air Temperature


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A =

Total Body HeatGain / Loss

B =

Effect of Air Temperature & Heat Loss

Dry Heat Loss(convection +radiation)

C =

Wet Heat Loss(evaporation)


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Humidity


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RH Relative Humidity (%)

DP Dew Point temperature (F)

Measures of Humidity

WB Wet-Bulb temperature (F)

W Humidity ratio (lb,water/ lb,air)


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Air Velocity


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Results: background survey--

air movement preference question

want less 4%

(n=4)

want more 38%

want less 4%

(n=4)

Field Studies: air movement preference

People want more air movement,not less, even in winter

Summer, n=104 Winter, n=95

(n=55)

(n=45)

(n=36)

(n=55)


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Mean Radiant Temperature


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Mean Radiant Temperature


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Operative Temperature

combines air & mean radiant temp.


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Measurable factors that influence thebodys heat balance


1. Air temperature 1. Activity

Major Variables Influencing Thermal Comfort

2. Humidity 2. Clothing3. Air Velocity

4. Mean radiant temperature


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Activity Metabolic Heat Production

1 MET = 18.4 Btu/ft2-hr, sedentary activity

1 met 1.4 met 3.0 met 4.0 met

Table of activity & met values See Lecture Handout, p. 25


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Clothing Insulation Value

1 CLO = 0.88 (hr-ft2-F/Btu), typical 3-piece suit

0.2 clo 0.8 clo 1.0 clo 3.0 clo

Table of clothing & clo values See Lecture Handout, p. 25


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Clothing Insulation Value

1 CLO = 0.88 (hr-ft2-F/Btu), typical 3-piece suit

0.2 clo 0.8 clo 1.0 clo 3.0 clo

Table of clothing & clo values See Lecture Handout, p. 25


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0.9 1.3 clo


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0.7 0.8 clo


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0.1 0.4 clo


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0.8 clo 0.5 clo 0.8 clo

1.6 met 2.2 met 2.3 met

70F 70F 64F


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7th inning stretch


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Research Standards Practice

Thermal ComfortStandards & Research


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How is comfort measured? 7-point Thermal Sensation Scale

Comfort or Satisfaction is associated

with thermal sensations

+3 Hot

+2 Warm

+1 Slightly warm0 Neutral

-1 Slightly cool

-2 Cool

-3 Cold

Comfortable


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Predicted Mean Vote (PMV) and

Predicted Percent Dissatisfied (PPD)

You cant satisfyeveryone!

Min = 5% dissatisfied


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idityR

atio

ASHRAE* Thermal Comfort Standard

Operative Temperature

H

u

Two comfort zonesbased on assumed

seasonal clo values

* American Society of Heating, Refrigerating, and Air-Conditioning Engineers


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Laboratory experiments, based on:

4 (environmental) + 2 (personal) variables

Ask people about thermal sensation

--- ---

Basis for existing standards

Develop heat-balance model of the

human body & comfort responses

Comfort wisdom = uniform & steady


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Reality check: Laboratory Real buildings

One-size-fits all: Universally applied to allclimates, cultures, and building types

Ener intensive: Broad a lication of narrow

Problems with existing standards

setpoints exaggerates the need for a.c.


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Based on field data

3 types of adaptation:- physiological- behavioral

A new approach: Adaptive Thermal Comfort

- psyc o og ca

Satisfaction influenced byexpectations & context

Outdoor climate is animportant influence

Overview of research


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22,000 sets of raw data from existing studies- physical and subjective data

- 160 buildings, 4 continents

Separate analysis for :

Overview of research

- air-conditioned (HVAC)- naturally ventilated (NV)

Statistical modelsproduced a new

standard for NV buildings

SELECTED RESULTS


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26

27

,Top(oC)

Observed: Field-based adaptive model

Predicted: Lab-based PMV model

SELECTED RESULTS

Observed vs. predicted comfort incentralized HVAC buildings

20

21

22

23

24

25

-5 0 5 10 15 20 25 30 35

outdoor temperature index, ET* (oC)

indoo

rcomforttempera

ture

SELECTED RESULTS


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26

27

,Top(oC)

Observed: Field-based adaptive model

Predicted: Lab-based PMV model

SELECTED RESULTS

Observed vs. predicted comfort innaturally ventilated buildings

20

21

22

23

24

25

-5 0 5 10 15 20 25 30 35

outdoor temperature index, ET* (oC)

indoo

rcomforttempera

ture

D i E l b ildi th t h d th Ad ti


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Design Examples buildings that have used the Adaptive

Comfort Standard in designing for natural ventilation

San Francisco Federal Building

Evergreen Valley College

Northern Arizona University

Kirsch Environmental Science Building

UC San Diego office building Rand Corporate Headquarters

Pier 1 Embarcadero

IB Tower Lobby Renovation Alley 24 speculative office building

Angola classrooms

New directions in thermal comfort


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Thermal monotonyor thermal delight?

The role of control?

New directions in thermal comfort

Mixed-mode:the best of

both worlds?


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Announcements Midterm

Midterm Review Session

Sunday, March 1, 7-9 pm, Room 112Midterm next Thursday, March 5

Mater a covere t roug t s week

See example Midterm on web

Closed book exam.

Equations, property values, etc. provided

Bring: pencil(s), eraser, calculator, LOFSAC


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Remember the Building Bioclimatic Chart ??

re(T)

Relative Humidity (RH)

Temperat

Same Chart Different Format


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Same Chart Different Format

Psychrometric Chart

or

peratu

re

Relative Humidity (curved lines)

Temperature

Hum

idtyRati

Dew

pointTe


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or

peratu

re

Relative Humidity (curved lines)

Psychrometric Chart

Temperature

Hum

idtyRa

ti

Dew

pointTe


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Documents

12 Thermal Comfort GB 2009color