5 year old house - finished attic. Permanent stairs, carpet, heat, ceilings, drywall - completely finished. The insulation is spray foam (open cell) directly on the underside of the roof deck (min - R19) and on the inside of the exterior walls. There was ridge vent originally installed, but sealed up with spray foam (closed cell). What I am trying to explain here is that the entire attic is within the building envelope - with the exception of a sloped ceiling, it looks like any other room in the house. I had the building envelope tested (blower door test) and there was very minimal air leakage anywhere in the house and what was detected was remediated.
There are knee walls and a dropped ceiling after the underside of the roof joists pass 9' (roof peak is at 13'), but these are just studs and drywall - no isulation. The spaces they create are still inside the building envelope (insulation is on the exterior walls only). The space behind the knee walls are accessible via access panels (used for storage) and there is no appreciable temperature difference in summer or winter in these spaces. The area above the ceiling is closed off and I cannot measure.
The problem is, the attic gets really hot in the summer. I can feel a temperature gradient as I walk up the stairs and have measured the bedrooms on the floor below at 75 (at the ceiling) and the attic ceiling at 85 degrees. My thought is to get a bathroom exhaust (or 3) inthe ceiling and vent the space that way. Any pros / cons / other suggestions?
The attic is 800 sq ft and the finished space 5600 cu ft.