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Heat loss, qfloor from a Floor to a Crawl Space:

^floor = qperimeter + qground + qair exchange

Where:

ti = indoor temperature, °F to = outdoor temperature, °F tg = ground temperature, °F

o tc = crawl space temperature, °F

Af = floor area, ft2

Ap = exposed perimeter area, ft2

Uf = floor heat transfer coefficient,

Ug = ground coefficient, Btu/hr-ft2°F

Up = perimeter heat transfer coefficient,

Btu/(hr-ft2-°F) Vc = volume of the crawl space, ft3

pcp = volumetric air heat capacity

(0.018 Btu/(ft3-°F) 0.67 = assumed air exchange rate (volume/hour)

The above equation must be solved for tc the crawl space temperature. Then the heat loss from the space above to the crawl space, using the floor U-factor can be calculated.

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