passive design for thermalcomfort_1.pdf

17-4-2013

1

LECTURE N 2- Thermal comfort -

2

Lecture contributions

Coordinator of the lecture: Prof. Ing. Karel Kabele, CSc., Faculty of Civil Engineering, CTU in Prague,

[email protected] , http://tzb.fsv.cvut.cz/

Contributors: Ing. Pavla Dvokov, PhD., Faculty of Civil Engineering, CTU in Prague,

[email protected], http://tzb.fsv.cvut.cz/ Prof. Ing. Karel Kabele, CSc., Faculty of Civil Engineering, CTU in Prague,

[email protected] , http://tzb.fsv.cvut.cz/ Manuela Almeida, [email protected], Sandra Silva,

[email protected] , University of Minho (UMINHO) Marie-Claude Dubois, M. Arch. PhD, [email protected]

IDES

-EDU

17-4-2013

2

Hygrothermal microclimate Indoor environment state from the viewpoint of thermal

and moisture flows between the human body and itssurrounding

Thermal comfort

state of mind which expresses satisfaction with the thermal environment

3

MODELLING THERMAL COMFORT

Field study method

Heat exchange method

4

IDES

-EDU

17-4-2013

3

5

Heat Exchange between the Human Body and the Environment

Metabolic Rate M degree of muscular activities, environmental conditions body size.

Heat loss Q Respiration Convection Radiation Conduction Evaporation

Body thermal balance equationM=Q comfortM>Q hotM

17-4-2013

4

7

Thermal comfortI - Clothing Insulation (m2.K/W)

1 clo=0,155m2.K/W

clo 3,5

8

Thermal comfortM - Metabolic Rate (m2.K/W)

1Met = 58,15 W/m2IDES

-EDU

17-4-2013

5

Metabolism depends on physical activity

The proposed values relateto a man of 70 kg with body surfaceequal to 1.8 m2

Corrections for other individuals :

- Weight: 1 W / kg- Female: 20%- Children: from -20 to -40%

Metabolism and activity

9

10

Environmental indices

Operative Temperature

where top = operative temperatureta = air temperaturetr = mean radiant temperature (MRT)hc = convective heat transfer coefficienthr = mean radiative heat transfer coefficient

rc

rrc

hhthth a

+

+=optIDES

-EDU

17-4-2013

6

Operative temperature The average between air temperature Ta

and the mean radiant temperature Trm :

va

TaaTT rmaop25,05,0

)1(+=

+=

11

describes the environment of radiation from one point in the room

depends on the temperature of the surrounding surfaces and exposure to these surfaces

[Source: Lechner N (2001) Heating, cooling, lighting. p. 44]

Mean radiant temperature(MRT)

12

IDES

-EDU

17-4-2013

7

13

Environmental indices Mean Radiant Temperature

where tr = mean radiant temperature Ti = temperature of the surrounding surface i,

i=1,2,....,n rn = shape factor which indicates the fraction of

total radiant energy leaving the clothing surface 0 and arriving directly on surface i, i=1,2,...n

273.T....Tt 4 4nrn41rr1r ++=

jj

jSjj

r S

TST

Mean radiant temperatureSimplified method

Tr can be determined from the measurement of globe temperature

Mean radiant temperature (MRT)

Ts1Ts2

Ts3

Ts4

Ts5Tr

14

IDES

-EDU

17-4-2013

8

What is your MRT today?

[Btiment Hewlett & Packard, Stockholm]

Mean radiant temperature(MRT)

15

1C 1,5C 2,5C2C

3C

4C

5C

0.60.81.01.21.41.61.82.02.22.42.62.83.03.2

0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 Clo

Act

ivit

[M

et] .

35

60

85

110

135

160

Act

ivit

[W

/m]

.

10C12C

14C16C

20C18C

22C24C

26C28C

Operative temperature

16

IDES

-EDU

17-4-2013

9

Humidity and temperature Dry-bulb temperature Wet-bulb temperature

17

http://www.dpi.nsw.gov.au/agriculture/horticulture/greenhouse/structures/evap-cooling

www.meted.ucar.edu

Psychrometric chart

18

Dry bulbtemperature

Relativehumidity %

Absolute humidity

Dew point

Wet bulb temperature

Enthalpy

TEMPERATURE

HUMIDITYRATIO g/kg

Fan

Wet bulbtemperature

Dry bulbtemperature

Wet sock

Air

IDES

-EDU

17-4-2013

10

Moisture Molliere diagram Psychrometric chart

19

Absolute humidity

20

the mass of dissolved water vapor, mw, per cubic meter of total moist air, Vnet: [g/m3]

A hygrometer is a device used for measuring the humidity of the air

http://en.wikipedia.org

IDES

-EDU

17-4-2013

11

Relative Humidity (RH) rh is the ratio of the partial vapor pressure of water to the

saturation vapour pressure of water at a certain temperature of the moist air

there are different standards concerning the rh in buildings likeEN 13779, VDI 3804, ASHRAE 62-2001

rh can become uncomfortable to the user of a building, if it iseither too low or too high

21

Relative Humidity depending on the geografical location, the lower limit of the

relative humidity can be a problem for example in new single-familiy houses or apartment houses with mechanicalventilation (compact units, semi-central systems,) duringwinter (e.g. in Austria)

One example: outdoor air temperature: -5C relative humidity of the outdoor air: 0,7 - what happens if this air is heated up to 22C? what will be th e relative

humidity?

22

IDES

-EDU

17-4-2013

12

Relative Humidity produced by

humans, if youcook, if you takea bath or a shower, byplants

23

http://en.wikipedia.org

Relative Humidity Monitoring example of an apartment with mechanical ventilation

(monitoring period one year , hourly data - recuperative heat recovery /no moistrecovery)

24

t_outdoor C t_indoor C

rh %ID

ES-E

DU

17-4-2013

13

Thermal comfort in Mollieres chart

LTZB/LATZ Laboratoe TZB, pracovn materil pro vuku, LS 2011/2012

Humidity ratio [g/kg s.v.]

Air

tem

pera

ture

[C]

SUMMER

WINTER

Effective temperature

26ASHRAE HANDBOOK

IDES

-EDU

17-4-2013

14

27

EN ISO 7730 ERGONOMICS OF THE THERMAL ENVIRONMENT -- ANALYTICAL DETERMINATION AND INTERPRETATION OF THERMAL COMFORT USING CALCULATION OF THE PMV AND PPD INDICES AND LOCAL THERMAL COMFORTCRITERIA (2005)

Thermal comfort

Definitions Psychological condition of satisfaction in relation

to thermal environment (ASHRAE 55-2004) No discomforts (FANGER) Feeling of well being physically and mentally

(European passive solar handbook) Conditions for which self-regulatory mechanisms of

the body are at a minimum level of activity(GIVONI)

28

IDES

-EDU

17-4-2013

15

29

Thermal comfort evaluation PMV index (Predicted

mean vote) PPD index (Predicted

percentage of dissatisfied)

0%10%20%30%40%50%60%70%80%90%

100%

-3 -2 -1 0 1 2 3PMV

PPD

Comfort measure: Predicted Mean Vote

-3 cold-2 cool-1 slightly cool0 neutral1 slightly warm2 warm3 hot

dissatisfied too warm

dissatisfied too cold

satis

fied

30

IDES

-EDU

17-4-2013

16

PMV and PPD

0%10%20%30%40%50%60%70%80%90%

100%

-3 -2 -1 0 1 2 3PMV

PPD

Satisfaction

PPD = 1 - 0.95 exp(-0.003353PMV4- 0.2179 PMV2 )

31

Fanger Equation

( )[ ]( )( )

( ) ( )( )

+=

FTmpmwm

pwmwmmPMV

a3070014.05867000017.015.5842.0

99.6573300305.0028.0036.0exp303.0

( ) ( )( ){ }

( ) FRwmTvTTh

TThfTTfF

cl

acl

aclmrtcl

=

=

+=

028.09.30806.12;38.2max

1096.34/1

448

32

IDES

-EDU

17-4-2013

17

Standard recommendationsEN ISO 7730 and ASHRAE 55-2004 :

-0,5 < PMV < +0,5 PPD < 10 %

Thermal comfort1st condition : Body heat balance

33

Parameters affecting thermal comfort.

Air temperature ................................ Ta [C] ou Ta [K] Mean radiant temperature ............... Tmrt [C] ou Tmrt [K] Air velocity ....................................... v [m/s] Partial pressure of water vapor ........ p [Pa] Metabolic rate of human body ......... M [Watt] External mechanical power ....................W [Watt] Body surface area ........................... A [m2] Specific activity......................................m = M/A [W/m2] Specific work ................................... w = W/A [W/m2] Thermal resistance of clothes ......... R [m2 K/W] or clothing ........................................ H [Clo] = R/0.155 The portion of clothed body surface f

34

IDES

-EDU

17-4-2013

18

Range of validity of the model of Fanger

Metabolism from 46 to 230 W/m (0.8 to 4 met); Clothing from 0 to 2 clo ; Air temperature from10 to 30 C; MRT from 10 to 40 C; Air velocity upto 1 m/s; Partial pressure of water vapor from 0 to 2700 Pa. environnement conditionn

35

36

Thermal comfort EN ISO 7730 parmeters especially for HVAC systems design Main parameters of IEQ in Appendix A of EN 12831 3 cathegories of thermal comfort according to PPD and PMV

PMV - predicted mean vote, PPD - predicted percentage of dissatisfied

Category of indoor thermal environment

Thermal state of the body as a wholePPD PMV

A < 6% 0,2 < PMV < + 0,2B < 10% 0,5 < PMV < + 0,5C < 15% 0,7 < PMV < + 0,7

Categories of thermal environment (EN ISO 7730)IDES

-EDU

17-4-2013

19

37

Optimal operative temperature

Indoor environment category A (PPD

17-4-2013

20

39

Temperature criteria for the design

Thermal comfort

According to EN ISO 7730 there are two conditionsfor thermal comfort

The heat balance of the individual is balanced withoutoverexertion of its self-regulatory mechanisms

1

There are no local discomforts due to:- air velocity- radiant assymetry- the vertical temperature gradient- floor temperature

2

40

IDES

-EDU

17-4-2013

21

Comfort: practical information

Summer (0,5 clo): 22 26 C

Winter (1 clo): 20 24 C

41

VERT. TEMP. GRADIENT

DRAUGHTRADIANT ASSYMETRY

FLOOR TEMPERATURE

Thermal comfort2nd condition : no local discomforts

42

IDES

-EDU

17-4-2013

22

Local thermal discomfortRadiant assymetry

43

Cold surfaces

Warm surfaces

GlazingPoorly insulated exterior wallCeiling and / or underfloor cooling

Glazing (sun)Ceiling and / or underfloor heatingRadiant heat emitter(lighting, heating, etc ...)

Local thermal discomfortRadiant assymetry

44

IDES

-EDU

17-4-2013

23

Radiant assymetry - effect

ASHRAE Handbook-Fundamentals45

Thermal stratification

Floor heating or cooling

Near mouth of heat/cold air supply

Local thermal discomfortvertical temperature gradient

46

IDES

-EDU

17-4-2013

24

Vertical temperature gradient

ASHRAE Handbook-Fundamentals47

Floor temperature

48

IDES

-EDU

17-4-2013

25

[Source: Ching & Adams (2003) Guide technique et pratique de la construction, p. 358]

The speed of air flow should be 10-50 feet per minute (ft / min) or 0,05-0.25 m / s, a higher speed may cause drafts

The colder the air temperature is the slowerair velocity should be

Local thermal discomfortAir velocity

49

Natural air flow in the room

Near a window or vents

Air conditioning (high rates of mixing)


50

IDES

-EDU

17-4-2013

26

[Source: Stein & Reynolds (2000) Mechanical and electrical p. 52]

The warmer air is, the largertolerance is .


51

52

ASHRAE STANDARD 55-2004 THERMAL ENVIRONMENTAL CONDITIONS FOR HUMAN OCCUPANCYID

ES-E

DU

17-4-2013

27

Thermal comfort

Standard 55a-1995 ASHRAE

Air temperature 68-78 F (20-26 C)

Relative humidity 20-80% (60% summer)

Air velocity 20-60 fpm (10-30 cm/s)

MRT T air

[Source: Stein & Reynolds (2000) Mechanical and electrical p. 43]

53

Thermal comfort

[Source: ASHRAE, Norme 55-2004

Standard 55-2004Vair > 0,20 m/s

54

IDES

-EDU

17-4-2013

28

Thermal comfortregulatory environment

[Source: ASHRAE, Norme 55-2004

Standard 55-2004

Vair < 0,20 m/ssummerwinter

55

56

EN 15251 INDOOR ENVIRONMENTAL INPUT PARAMETERS FOR DESIGN AND ASSESSMENT OF ENERGY PERFORMANCE OF BUILDINGS ADDRESSING INDOOR AIR QUALITY, THERMAL ENVIRONMENT, LIGHTING AND ACOUSTICS(1.12.2007)

IDES

-EDU

17-4-2013

29

57

Thermal comfort EN ISO 15251 parameters for the thermal comfort assessment in

buildings with different building services systems. Parameters useable for building energy performance calculations IAQ, thermal environment, lighting, acoustics

Category ExplanationI High level of expectation and is recommended for spaces occupied by

very sensitive persons (very young children, sick, elderly persons,...)II Normal level of expectation for new buildings and renovationsIII An acceptable, moderate level of expectation, for existing buildings

IV Acceptable for a limited part of the year

58

Thermal comfort Boundary conditions for the design of mechanicaly heated and

cooled buildings

Building type CategoryOperative (resultant) temperature (C)

Minimum for heating Maximum for cooling

Single office (cellular office)Sedentary ~ 1,2 met

I 21 25,5II 20 26III 19 27

Category of indoor thermal environment

Thermal state of the body as a wholePPD PMV

I < 6% 0,2 < PMV < + 0,2II < 10% 0,5 < PMV < + 0,5III < 15% 0,7 < PMV < + 0,7IV >15% 0,7 < PMV

PMV < - 0,7IDES

-EDU

17-4-2013

30

59

Indoor air quality Design criteria for indoor air quality (non residental) Polluting source

people building operation

Category PPD Airflowl/s/pers.Recommended ventilation rates, pollution from building itself [l/s.m2]

Very low pollution Low pollution Higher pollutionI 15 10 0,5 0 1,00 2,00II 20 7 0,35 0,70 1,40III 30 0,30 0,40 0,80IV > 30 < 4

Temperature changes over time

Changes of temperature within a day

Temperature changes from day to day

Seasonal changes in temperature

60

IDES

-EDU

17-4-2013

31

61

FIELD STUDIES AND THE ADAPTIVE MODEL

Adaptive model of thermal comfort

If a change occurs in the thermal environment which tends to producediscomfort, people will respond in ways that tend to restore their comfort.(Humphreys, 1997)

62

Adaptive model of thermal comfortThe types of action which can be taken to adapt to the indoorclimate are:

Modifying the internal heat generation

Modifying the rate of body heat loss

Modifying the thermal environment

Selecting a different environment

62

IDES

-EDU

17-4-2013

32

Adaptive model (DeDear et Bragger)

eop 31.08.17 +=

15

171921232527

293133

0 10 20 30 40Temprature extrieure moyenne [C]

.

Adaptif

EN-ISO

Average outdoor temperature [C]

Indo

or

ope

rativ

ete

mpe

ratu

re[C

]

63

64Runming Yao; Baizhan Li and Jing LiuRunming Yao; Baizhan Li and Jing Liu

Adaptive model

IDES

-EDU

17-4-2013

33

65


In buildings with HVAC systems the comfort temperature adjust to EN ISO 7730 model.In buildings without mechanical systems the occupants adapt themselves in way that EN ISO 7730 does not predict.

Dear et al.

66

Adaptive model of thermal comfortThere may be defined three categories of adaptation to indoorclimate (Folk 1974, 1981, Goldsmith 1974, Prosser 1958, Clark andEdholm 1985):

1. Behavioural Adjustment;2. Physiological;3. Psychological.

The three components of adaptation to indoor climate (adapted from ASHRAE RP 884)

Adaptation to Indoor Climate

AdjustmentBehavioural /technological changes to the heat balance

(clothing and activity,personal environmental

control)

AcclimatizationLong term physiological

adaptation to climate (genetic adaptation)

HabituationPsychological adaptation

changing expectations (expectations and thermal

memory, adaptive opportunity)

IDES

-EDU

17-4-2013

34

67

Adaptive model of thermal comfortBehavioural Adjustment

Includes all modifications a person might consciously, or unconsciouslymake, which will modify heat and mass fluxes governing the bodysthermal balance. The adjustment may be defined in terms of threesubcategories:

a) Personal adjustment: adjusting to the surroundings by changing personalvariables, such as clothing, activity, posture, eating/drinking hot/cold foodor beverages, or moving to a different location;

b) Technological or environmental adjustment: modifying the surroundingsthemselves, when control is available, such as opening/closing windows orshades, turning on fans or heating, blocking air diffusers, or operatingother HVAC controls, etc.; and

c) Cultural adjustments, including scheduling activities, siestas, dress codes.

68

Adaptive model of thermal comfortPhysiological

The physiological adaptation include all of the changes in the physiologicalresponses which result from exposure to thermal environmental factors,and which lead to a gradual diminution in the strain induced by suchexposure. Physiological adaptation can be divided into at least twosubcategories:

a) Genetic adaptation: alterations which have become part of the geneticheritage of an individual or group of people, but developing at time scalesbeyond that of an individuals lifetime, and

b) Acclimation or Acclimatization (used interchangeably here): changes in thesettings of the physiological thermoregulation system over a period ofdays or weeks, in response to exposure to single or a combination ofthermal environmental stressors.

IDES

-EDU

17-4-2013

35

69

Adaptive model of thermal comfortPsychological

The psychological adaptation to indoor climate refers to an alteredperception of, and reaction to, sensory information. Thermal perceptionsare directly and significantly attenuated by ones experiences andexpectations of the indoor climate.This form of adaptation involves building occupants comfort set pointswhich may vary across time and space.Relaxation of indoor climatic expectations can be likened to the notion ofhabituation in psychophysics - repeated or chronic exposure to anenvironmental stressor leading to a diminution of the evoked sensationsintensity (Glaser 1966, Frisancho 1981).

70

Adaptive model of thermal comfortThe generic term adaptation might be interpreted as thegradual diminution of the organisms response to repeatedenvironmental stimulation. As used in ASHRAE RP-884,adaptation subsumes all physiological mechanisms ofacclimatization, plus all behavioural and psychological processeswhich building occupants undergo in order to improve the fitof the indoor climate to their personal or collectiverequirements.

70

IDES

-EDU

17-4-2013

36

71


ASHRAE RP 885

72


i min = 0,33 rm + 18,8 - 3

i max = 0,33rm + 18,8 + 3

The operative temperatures (room temperatures) presented are valid for office buildings andother buildings of similar type used mainly for human occupancy with mainly sedentaryactivities and dwelling, where there is easy access to operable windows and occupants mayfreely adapt their clothing to the indoor and/or outdoor thermal conditions.

EN 15231

IDES

-EDU

17-4-2013

37

Models of comfort can: predict the comfort that prevails in a building of a

new type design buildings providing good comfort size and position the heating and cooling

systems according to the comfort requirements Increase tolerance in naturally ventilated buildings

73

Predict the comfort

Radiant temperature in a room with a coldwindow and radiator 36

17

74

IDES

-EDU

17-4-2013

38

References and relevant bibliography

Bluyssen Philomena M.: The Indoor Environment Handbook How to Make Buildings Healthy and Comfortable, Earthscan ltd (United Kingdom), 2009, ISBN-13: 9781844077878

http://new-learn.info/learn/packages/mulcom CIBSE: Guide A: Environmental design, ISBN: 1903287669 Ching & Adams (2003) Guide technique et pratique de la construction, p.

358-359. EN ISO 7730 Ergonomics of the thermal environment - Analytical

determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria (2005)

ASHRAE Standard 55-2004 Thermal Environmental Conditions for Human Occupancy

EN 15251 Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics(1.12.2007)

BRAGER, G. S., de DEAR, R. J.: Thermal adaptation in the builtenvironment: a literature review, Energy and Buildings 27, 1998

IDES

-EDU

passive design for thermalcomfort_1.pdf

Documents

Transcript of passive design for thermalcomfort_1.pdf