Opaque-Envelope Conduction Cooling Load (Sol-Air CLTD)
The conduction cooling load through a sunlit wall or roof: U x area x the sol-air CLTD, which for a dark roof in summer can run 70 F or more against a 95 F design day because the sun heats the surface well above the air. Dropping the surface's solar absorptance with a reflective cool-roof membrane cuts the load far more than the air temperature would suggest - the entire case for a cool roof in one comparison. The U-factor is the whole-assembly value; the CLTD is from the ASHRAE/ACCA table. One Manual J component, not the stamped load sheet.
Formula and source
q_cond = u_factor x area_ft2 x cltd_f.
ASHRAE / ACCA Manual J opaque-envelope cooling load (Q = U x A x CLTD, the CLTD being the sol-air cooling-load temperature difference), by name; the relation is public.
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