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Christopher A. Steele wrote:

Sometimes it gets so hot around here it's difficult to sleep at night
(to the point I sometimes have to get up two or three times to cool
off in the shower just to get comfortable for a few minutes).

Sir Turtle might suggest a space heater to raise the room temp to 95 F,
which he describes as "too cold," vs 60 F ("too hot" :-)

I'm curious: given 'x' ambient temperature in my bedroom at night (and
'y' relative humidity, I suppose) and closed bedroom windows and
doors, how do I calculate the amount of heat (heat load??) that has to
be 'removed' from my body so that I can sleep comfortably...

An ASHRAE-standard 154 pound human dissipates 253 Btu/h when sleeping.

Is there a formula?

Sure. ASHRAE-standard 55-2004 ("Thermal environmental conditions for human
occupancy") defines two "comfort zones," winter (with a clo = 1 clothing
thermal resistance) and summer (clo = 0.5.) Its BASIC program estimates
the Predicted Mean Vote (PMV: +3 hot, +2 warm, +1 slightly warm, 0 neutral,
-1 slightly cool, -2 cool, and -3 cold) and the Predicted Percentage
Dissatisfied (PPD) based on clothing, activity, metabolic rate, external
work, air temp, mean radiant temp, air velocity, and RH...

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 (%) make one of RH or PA non-zero...
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'intermed iate 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 HCFHCN THEN HC=HCF ELSE HC=HCN
380 XN=(P5+P4*HC-P2*XF^4)/(100+P3*HC)
390 N=N+1
400 IF N150 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 MW58.15 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

T (C) 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

The first 4 lines are the winter comfort zone corners.
The second 4 lines are the summer comfort zone corners.

An average person is "comfortable" when the PMV = 0.

"Travis Jordan" writes:

The ASHRAE calculations for heat gain assume 600 BTU/H per person.
That's 150 calories / hour.

That works for large Btus.

mj writes:

Being uncomfortable typically has more to due with humidity than
temperature...

The ASHRAE 55-2004 comfort zone disagrees, based on surveys of 21,000 people.

Nick


This is Turtle.

if you can't explain %RH as to temperature that most people likes , you just
explaining what you think and have no ideal of the real world is thinking. You
sure quote the ASHRAE a lot but I wished you could understand it in real life
terms.

Here is one for you. 5%RH or there about and 90ºF = pretty cool. What do you
think and don't try to justify your reply with references but explain it in real
life terms. Nick you live in a book and if I took your book away from you. You
would be speechless.

TURTLE