Infiltration Heating / Cooling Load (Sensible + Latent)
The load the air the envelope leaks adds to the design day: sensible Qs = 1.08 x cfm x delta-T and latent Ql = 0.68 x cfm x delta-grains, from the natural infiltration cfm a blower-door test produces. In cooling the latent half (the moisture the leaking air drags in) is nearly as large as the sensible, which is why air-sealing pays back on both design days. The 1.08 and 0.68 are sea-level standard-air constants. The infiltration component only, not a stamped Manual J.
Formula and source
q_sensible = 1.08 x cfm x delta_t_f; q_latent = 0.68 x cfm x delta_gr; q_total = q_sensible + q_latent.
ASHRAE Handbook of Fundamentals air-side sensible (q_s = 1.08 x Q x dT) and latent (q_l = 0.68 x Q x dW_gr) equations, by name; the 1.08 and 0.68 are the sea-level standard-air constants.
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