Insulation for Rooms Adjacent to Garage Attic

Factual Questions
1

I have a couple of rooms that share part of their walls with the attic of the attached garage. These rooms are also the coldest in winter and hottest in summer (although one is much worse than the other). I’ve had an HVAC guy down and he measured the airflow from the vent and said it was good. So I’m wondering if the wall that’s connected to the attic is perhaps not properly insulated.

I went into the attic and the wall has the regular fiberglass insulation. But unlike the walls to the exterior of the house, which also have plywood sheating and PVC siding, there’s nothing beyond the exposed fiberglass.

Is this significant? And if so, what should I do about it? (Foam boards in the attic?)

2

exposed fiberglass bats are not as effective insulation as enclosed.

you would want that wall have as much insulation as an outside wall ideally. rigid polyurethane foam board has twice the insulation as fiberglass batts for the same depth. if the walls are 4 inches then you would best use the rigid foam.

3

We had a similar problem with a room above our garage. We tried a bunch of stuff, with no real luck. What finally made a difference was hiring an insulation specialist company to come out and make a recommendation. They had a heat-sensing camera that they took a bunch of pictures with, and were able to pinpoint exactly where the issue was and fix it.