[Greenbuilding] ashrae 55 and perception

[Nick Pine]

Alan Abrams <alan at abramsdesignbuild.com> writes:

>   <ASHRAE would say you'd be cooler in the dark>
>
>   holy cow, Nick--my hat's off to ASHRAE 55 (on second thought maybe i 
> should leave  it on, to increase the shading coefficient :-)  the point of 
> my previous  post  was  simply  in favor of vegetation as an element that 
> contributes to a sense of comfort.  You've provided an objective 
> foundation for my direct but uninformed observation.  I still don't think 
> it conflicts with the notion that associations that originate from sensory 
> experience can influence  perception,  and  that even an image can 
> influence physical response--as Hugh Hefner would surely corroborate.

I'm not sure my previous email to you went to the list:

*********************************************
Hi Alan,

>i'd never suggest a green roof as a substitute for insulation--

Me neither :-)

>...  beyond that, howver, i'd like to put forth the proposition that there 
>some factors related to human comfort and perception that cannot be readily 
>quantified.

Have you seen the ASHRAE 55-2004 comfort standard? It costs about $50 and 
contains the BASIC program below. They rate comfort with a "predicted mean
vote" from -3 (very cold) to 0 (comfortable) to +3 (very hot), with a 
comfort zone bounded by a PMV from -0.5 to +0.5, based on surveys and 
experiments involving about 22,000 people.

>living in the inner 'burbs around washington dc, where the summers can be a 
>brutal combination of heat and humidity, i've found that you can be 
>reasonably comfortable sitting outside in areas where the tree canopy is 
>heavy, moreso that under the shade of an awning or overhang, with open sky 
>above.

There's more open sky above you if you sit near the edge of a shadow, vs 
deep under an overhang. This lowers the mean radiant temperature your body
sees, which is the product of each surrounding temp and its fractional solid 
angle of the sphere surrounding you. A clear sky can be very cold on a hot 
day. Phoenix redesigned some outdoor train stations to lower the MRT...

>it's as though the trees contain a lens of chilled air--even on breezy 
>days.

Breezes help too.

>i suspect it has something to do with green light and color, not just 
>ground and air temps.  whether this is hardwired in our limbic systems, or 
>learned associations, i'm not prepared to say, but the observation remains 
>that vegetation can provide a sense of comfort.

ASHRAE would say you'd be cooler in the dark, with no radiant green warming 
:-)

Nick

50 CLO = 1'clothing insulation (clo)
60 MET=1.1'metabolic rate (met)
70 WME=0'external work (met)
80 TA=19.6'air temp (C)
90 TR=19.6'mean radiant temp (C)
100 VEL=.1'air velocity (m/s)
120 RH=86'relative humidity (%)
130 PA=0'water vapor pressure
140 DEF FNPS(T)=EXP(16.6536-4030.183/(TA+235))'sat vapor pressure, kPa
150 IF PA=0 THEN PA=RH*10*FNPS(TA)'water vapor pressure, Pa
160 ICL=.155*CLO'clothing resistance (m^2K/W)
170 M=MET*58.15'metabolic rate (W/m^2)
180 W=WME*58.15'external work in (W/m^2)
190 MW=M-W'internal heat production
200 IF ICL<.078 THEN FCL=1+1.29*ICL ELSE FCL=1.05+.645*ICL'clothing factor
210 HCF=12.1*SQR(VEL)'forced convection conductance
220 TAA=TA+273'air temp (K)
230 TRA=TR+273'mean radiant temp (K)
250 TCLA=TAA+(35.5-TA)/(3.5*(6.45*ICL+.1))'est clothing temp
260 P1=ICL*FCL:P2=P1*3.96:P3=P1*100:P4=P1*TAA'intermediate values
300 P5=308.7-.028*MW+P2*(TRA/100)^4
310 XN=TCLA/100
320 XF=XN
330 N=0'number of iterations
340 EPS=.00015'stop iteration when met
350 XF=(XF+XN)/2'natural convection conductance
360 HCN=2.38*ABS(100*XF-TAA)^.25
370 IF HCF>HCN THEN HC=HCF ELSE HC=HCN
380 XN=(P5+P4*HC-P2*XF^4)/(100+P3*HC)
390 N=N+1
400 IF N>150 GOTO 550
410 IF ABS(XN-XF)>EPS GOTO 350
420 TCL=100*XN-273'clothing surface temp (C)
440 HL1=.00305*(5733-6.99*MW-PA)'heat loss diff through skin
450 IF MW>58.15 THEN HL2=.42*(MW-58.15) ELSE HL2=0'heat loss by sweating
460 HL3=.000017*M*(5867-PA)'latent respiration heat loss
470 HL4=.0014*M*(34-TA)'dry respiration heat loss
480 HL5=3.96*FCL*(XN^4-(TRA/100)^4)'heat loss by radiation
490 HL6=FCL*HC*(TCL-TA)'heat loss by convection
510 TS=.303*EXP(-.036*M)+.028'thermal sensation transfer coefficient
520 PMV=TS*(MW-HL1-HL2-HL3-HL4-HL5-HL6)'predicted mean vote
530 PPD=100-95*EXP(-.03353*PMV^4-.2179*PMV^2)'predicted % dissatisfied
540 GOTO 580
550 PMV=99999!:PPD=100
580 PRINT TA,RH,CLO,PMV,PPD

 19.6          86            1            -.4778556      9.769089
 23.9          66            1             .4732535      9.676994
 25.7          15            1             .5239881      10.74283
 21.2          20            1            -.4779105      9.770202
 23.6          67            .5           -.4747404      9.706658
 26.8          56            .5            .5145492      10.53611
 27.9          13            .5            .5003051      10.23146
 24.7          16            .5           -.4883473      9.982468

Innova AirTech Instruments used to have an excellent comfort web site. Now 
they may mail you a 30 page booklet.

http://www.impind.de.unifi.it/Impind/didattica/materiale/microclima/innova/thermal.htm