plug in temps for your local area .....

http://www.infoplease.com/ipa/A0004587.html

Steve Spence
Dir., Green Trust
http://www.green-trust.org

Bughunter wrote:
I don't live in Philadelphia. What should I do?

wrote in message
...

Phila has an average daily min and max of 67.2 and 86.1 F in July. Two A
ft^2
vents with one-way plastic film dampers and a 16 ft height difference and
a
DT (F) temp diff would allow 16.6Asqrt(16DT) cfm to flow at night, cooling
a house by cfmDT Btu/h. What would the average July temp be in a house
with
10K Btu/F of thermal capacitance and 200 Btu/h-F of conductance and no
internal
heat gain and 2 4'x4' vents with a 16' height difference, and no fan?

10 PI=4*ATN(1)
20 TH=76'initial house temp (F)
30 FOR D=1 TO 100'simulate 100 average July days
40 FOR H=0 TO 23 STEP .1
50 TA=(86.1+67.2)/2+(86.1-67.2)/2*SIN(2*PI*H/24)'outdoor temp (F)
60 IC=(TH-TA)*200'conductive loss (+) or gain (-)
70 IF THTA THEN IV=16.6*16*SQR(16)*(TH-TA)^1.5 ELSE IV=0'vent cooling
(Btu)
80 TH=TH-(IC+IV)/10000*.1'new house temp (F)
90 NEXT H
100 NEXT D
110 PRINT TH

75.96505 (close to the average daily temp) with no vent

69.50536 (2.3 F above the min) with 2 4'x4' vents

With a higher house conductance, the vents make less difference, eg 73.3
vs 69.5 F at 1000 Btu/h-F. The vents above would move a 24-hour average
16.6x16sqrt(16(76.7-69.5)) = 2851 cfm, comparable to a whole-house fan.
With humidity sensing and motorized dampers, they could help heat a house.

Nick