Why do northern homes vent their attic spaces and southern homes spray icynene w/ non venting?
Cant say about the south as I only work New England. Northern venting- Venting a attic in cold weather will slow the melting of any snow on the roof (snow melting to fast is what causes the monster ice dams) now if the snow don’t melt and to much accumulates you now have concerns and maybe a serious issue with snow loads (possibly clasping your roof). I would rather deal with the ice dams myself. Now for venting a attic in warm weather it will keep the temperature of your asphalt shingles down and prolong there life with out a doubt.a warm attic with no ventilation will heat the roof probably to the point that shingles become so soft they tear right off the nails. This can also happen from improper nailing. Sinking the nails to deep while nailing with air pressure (pressure being to high) will penetrate the shingle making the shingle able to break loose and end up on the ground. You need to have the nail sit flush with the shingle for proper nailing. Now add no ventilation to improper nailing you will have many problems keeping them shingles on the roof.