Heat Loss For Below Grade Walls
Qb = U x HTDh x Area
Qh = Heat flow out of surface, Btuh
U = Below grade U-Value (heat transfer coeff.) from Table 4A Manual J 8, Btuh/ft²·°F
HTDh = Winter temperature difference (inside temperature - outside temperature), °F
Area = Net area of surface, square feet (ft²)
Ref: Manual J 8 - Page 3-2
Note: Below grade HTM values, defined by the equation HTMh = U x HTDh, are determined from the winter temperature difference, material type, and insulation.