While we’re in the attic space I want to point out a few things about a foam condition attic. If you notice how the foam covers the rafters, well the rafters are two by sixes, that means I have at least about a five and a half to six inch thick foam on top.
The reason that’s important is to control the dew point, I want the dew point to be beyond that of the decking above it. That keeps the moisture out of the plywood or OSB whichever you use on the decking. The next point I want to point out are the ducting system if you notice the ducts are set down below the rafters. What that does it allows me to have my five and a half inches of foam covering the rafters. Otherwise if the ducts block it I can’t get my foam to where it’s supposed to be.
The next thing is the attic temperature, the attic temperature of conditioned attic space is about 10 percent of the ambient temperature of the living area. Now the ambient temperature of the living area is the average temperature of the living space below us. So it’s conditioned by the attic through the thermal transfer of the temperature through the sheetrock into the attic area and thus is why they call it a conditioned attic space.