Can one think about sun shining on roofs and walls in terms of delta-T?
Any resources to help think about this would be great.
Many discussions of heating vs cooling include a statement something to the effect of, “in winter the delta-T can be 80°F or more, but in summer even on a 100°F day the delta-T is only 30°F”.
Sure, that makes sense, but what about when sun is shining on a surface (roof or wall)? Can we still think about that in terms of delta-T? ie something like, “The sun heats the outside of the wall/roof to ~140°F, so the delta-T is something like 70°F” (for periods of the day!) (I’m making those numbers up, but thermometers do show temps that high in the mid-afternoon sun here in Austin, TX). Or does the radiant vs conduction stuff render that pointless?
Or let me ask this another way: why aren’t the parts of the walls that are hit with direct sun (in cooling climates) treated differently in insulation materials than other walls? Yes, they are with windows/window-loads, but not the rest of the wall. Either in terms of R-value or in terms of thermal mass (accounting for the fact that the elevated energy those walls receive is sometimes short lived during the day)?
Apologies if that makes no sense 🙂
GBA Detail Library
A collection of one thousand construction details organized by climate and house part