I have a two-story house. Half the house has a cathedral ceiling (which will be left as is) and the other half has a traditional attic with no soffits. The only ventilation in the attic comes from two gable vents at each end of the house.
How should I insulate this type of attic? I am contemplating adding insulation to the bottom of the roof deck and adding more insulation to flooring in attic; I think this is called a sealed attic. Is this appropriate for my climate?
Best Answer
If I were building the house in southern California then I wouldn't do this, especially if you were using asphalt shingles.
An unventilated attic in a warm climate like this can get extremely hot and will greatly decrease the life expectancy of asphalt shingles. Over time they will start to curl prematurely from the heat. If I were to do this I would insist the following courses of action:
Heavily insulate without sealing gables
Have at least a 1 foot overhang with ventilated soffits
If 1 foot overhang is not possible, then install an attic fan to assist in proper ventilation of the attic
If neither of these are possible then forgo asphalt shingles for something more appropriate for extreme heat like terracotta or slate shingles.