912 Quantifying Building Envelope Performance

The rate of heat transfer through the building envelope will be found to be related to the following important variables:

1. Indoor and outdoor temperature;

2. Conductivity of the individual envelope components; and

3. The square footage of each of the envelope components.

For a particular building component exposed to a set of indoor and outdoor temperature conditions, these variables are often expressed in equation form by the following:


q = the component heat loss, Btu/hr

U = the overall heat transfer coefficient, Btu/ (hr-ft2-°F)

the area of the component, ft2 the indoor temperature, °F

To = the outdoor temperature, °F

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