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tikitime · 07-22-2008, 05:35 PM

Please take this with a grain of salt ... lifted from MFG website
http://www.ecoology.com/physics_101.htm
.....

The amount of heat energy that gets into the body of your building is determined by the formula

Qin = U x (Troof - Tinside).

Let's look at an example of what this formula means. For this example, we will take a value of .35 for the constant, "U". On a day where the air temperature reaches 70 degrees or more, it is quite likely that the roof will see a temperature of about 165 degrees F. Assuming that you keep your building at 78 degrees at floor level, the underside of your roof will probably be about 90 degrees. The formula then becomes;

Qin = .35 x (165 - 90) = 24 BTU/Hr/Square foot

For a 40,000 square foot building, 960,000 BTU's per hour get in.

By definition, one ton of air conditioning is equal to 12,000 BTU/Hr. You then need 80 TONS of air conditioning to remove this heat energy.

According to our physics professor, and the laws of physics, one gallon of water requires [absorbs] 8,265 BTUs to evaporate - go from a liquid state to a gaseous state.

Water, properly applied to your roof, will remove most of that solar energy heating your roof. Instead of 165 degrees, your roof will be kept at a much cooler 95 to 100 degrees.

Our equation now becomes;

Qin = .35 x (100 - 90) = 3.5 BTUs/Hr/Square foot.
Everything is the same, except your roof is 90 degrees instead of 165 degrees. Now, your 40,000-foot building has

140,000 BTUs getting in, requiring 12 TONS of air instead of 80 TONS.

07-22-2008, 05:35 PM	#4 (permalink)
tikitime reformed fuel guzzler Join Date: Jun 2008 Location: Mobile, AL Posts: 4 The Bus - '01 Ford Excursion Limited Thanks: 0 Thanked 0 Times in 0 Posts	here it is... Please take this with a grain of salt ... lifted from MFG website http://www.ecoology.com/physics_101.htm ..... The amount of heat energy that gets into the body of your building is determined by the formula Qin = U x (Troof - Tinside). Let's look at an example of what this formula means. For this example, we will take a value of .35 for the constant, "U". On a day where the air temperature reaches 70 degrees or more, it is quite likely that the roof will see a temperature of about 165 degrees F. Assuming that you keep your building at 78 degrees at floor level, the underside of your roof will probably be about 90 degrees. The formula then becomes; Qin = .35 x (165 - 90) = 24 BTU/Hr/Square foot For a 40,000 square foot building, 960,000 BTU's per hour get in. By definition, one ton of air conditioning is equal to 12,000 BTU/Hr. You then need 80 TONS of air conditioning to remove this heat energy. According to our physics professor, and the laws of physics, one gallon of water requires [absorbs] 8,265 BTUs to evaporate - go from a liquid state to a gaseous state. Water, properly applied to your roof, will remove most of that solar energy heating your roof. Instead of 165 degrees, your roof will be kept at a much cooler 95 to 100 degrees. Our equation now becomes; Qin = .35 x (100 - 90) = 3.5 BTUs/Hr/Square foot. Everything is the same, except your roof is 90 degrees instead of 165 degrees. Now, your 40,000-foot building has 140,000 BTUs getting in, requiring 12 TONS of air instead of 80 TONS.