What High Range Should Your Attic Temperature Not Exceed?

by Scott
(Sherwood Park, AB. Canada)

Scott's Question: I always see ads like "improve your attic ventilation" and I thought that these ads were for resolving problems with moisture.

A few years ago I had aluminum soffits installed. I found out that the sub trade had installed the aluminum soffits onto the existing plywood sheeting soffit (which was what I wanted), but they didn't make the existing vent holes larger or remove the existing screening.

Last weekend I went up there and the temperature was 32 degree C when outside on the ground it was 27 degree C. Now I have no problems, but I am concerned with air flow and high temperatures. Am I too concerned or what is the best simplified solution I should take?

Dave's Answer: I don't think you should be too concerned. The maximum attic temperature recommended during the peak summer hour is 4.4 degrees C (40 degrees F) greater than ambient outside air temperature. Your difference is 5 degrees C. I would increase the air flow to get the temperature down, but not too much as you do not want to increase the damp air flow into the attic.

Check the amount of insulation above the living space. The higher the R rating the better.

The soffits are under the eaves. How many square inches do you have to allow the air to enter? This number should match the square inches of where the hot air goes out.

Do you have ridge vents, turbines and/or eve vents? Do not install a power ventilator. It will pull too much moisture into the attic.