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I Added R-38 Insulation to My Loft and It Stayed Ice Cold All Winter

Wes Tanaka
Stack of foil-faced rigid foam insulation boards leaning against a wall with a utility knife and tape measure
Stack of foil-faced rigid foam insulation boards leaning against a wall with a utility knife and tape measure · Martin Cooper from Ipswich, UK , CC BY 2.0

How I Fixed It

I caught a break: my drywall wasn’t up yet.

That gave me a clean shot at the studs, and I took it. I ran 1-inch rigid foam boards—foil-faced polyiso panels, to be exact—horizontally across every stud before the drywall went on.

Each 4-by-8 sheet added R-5 of continuous insulation and broke the thermal bridge cold. No more direct contact between freezing framing and the room.

I picked up enough panels at Home Depot to cover the space—about $480 for materials. I also grabbed longer drywall screws (you’re now going through foam plus drywall into the stud) and tubes of construction adhesive to seal every seam. That added another $90.

The difference hit me the first cold morning in February. The loft held at 68°F instead of sagging to 58°F. My heating bill dropped $40 a month, every month since.

Already have drywall up? You’re looking at a much bigger job—probably a full retrofit with permits, vapor barrier concerns, and structural questions about fastening through foam into old framing. Call an insulation contractor who knows thermal bridging. Don’t guess on this one.

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