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Therms

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AHerra
AHerra Member Posts: 15
in THE MAIN WALL
I was wondering if there is a formula or way to calculate how many therms of gas a 1200 sq ft house would use to maintain a 55 degree temperature. House is tight construction with double pane windows. Lots of sun exposure.

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  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,643
    Formula

    Around here (SF Bay Area) the heat loss for a tight house is around 17 BTU/sq. ft.  So:



    1,200 sq. ft. x 17 BTU/sq. ft.  = 20,400 BTU/hr.



    1 Therm = 100,000 BTU



    20,400 BTU divided by 100,000 BTU = .20 Therms per hour



    Of course, this is an approximation and the 17 BTU/sq.ft. heat loss is typical for a house being heated to 68°; at 55°, you will use much less fuel.  For a more accurate calculation, you will need a heat loss survey for your particular house at design conditions.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
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