Quote:
Originally Posted by MandoMan
Yes, heat rises, but an uninsulated attic that is easily 120° much of the year separated from the garage by half an inch of drywall with an R value of less than one radiates a LOT of heat, like a hot oven does or a hot car. If you don’t need to insulate an attic over an air-conditioned garage because heat rises, then why does the rest of your house have insulation in the attic? In your garage, the cooled air comes into contact with the hot drywall and is heated up.
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I agree. The insulation above the ceiling is absolutely the most important insulation in your house, but only above conditioned spaces. So, if you install a mini-split unit in your garage or in your lanai, you need to install at least R-30 insulation above the ceiling. The more the better. Having no ceiling insulation is like trying to fill a bucket with water when the bucket has a large hole in the bottom.