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

The Thermal Bridge Problem

Turns out wood doesn’t insulate—at least not compared to fiberglass.

A 2x6 stud conducts heat several times faster than the same thickness of insulation. So while my R-38 batts were doing their job in the cavities, every stud was a wide-open shortcut for cold air to bypass the whole system.

The building industry has a name for this: thermal bridging. And in a loft with a dozen studs per wall, I had built an entire expressway network.

I could have stuffed R-60 insulation between those studs and it wouldn’t have mattered. The framing itself was the problem, and no amount of fill in the bays would fix it.

The solution wasn’t about going deeper into the wall—it was about going over it.

If I could break the contact between the studs and the interior surface, I could stop the cold before it ever reached the room. That meant adding a continuous layer of something that didn’t conduct heat, right across the face of all that framing.

The question was what, and whether I could do it without tearing down walls I’d already finished.