When I had my roof redone, we discovered that the nails they were using to put up the plywood base for the new roofing went through the sides of my dormers. Apparently those surfaces are a single board thick.

That's not a lot of area, but it's still almost completely uninsulated surface. And I can't afford to steal too much space back.

Best thought I've had would be to put up foam insulation with wood trim around the edges that face into the room, use that to secure plasterboard over the face of the foam (for fire safety as well as for appearance), then mud/paint to merge it into the existing surfaces. That'd steal an inch or two from the width of the dormer space, but would help that surface.

Reasonable? Better answers?

(The end and ceiling/roof of the dormer seem to be normal framing. I'll deal with that if/when I'm ready to attack the place with blown-in.)

1 Answer 1


A Radiant Barrier would be an alternative to insulation in terms of reducing heat flow. It does not depend on the thickness of material, just the barrier facing an airspace. If the interior and exterior surfaces of the dormer are not thermally coupled, this would help to reduce heat conduction and also improve efficiency.

  • Given that I think that part of the dormer is solid straight through, I'd say right now they're about as coupled as shingle-over-sheathing-over-wood-over-plaster is likely to get...
    – keshlam
    Sep 12, 2014 at 21:27
  • I wasn't suggesting not to lose the inch or two mentioned in your question.
    – user23752
    Sep 12, 2014 at 21:34
  • So what would the construction look like, in this approach? Not something I've worked with....
    – keshlam
    Sep 12, 2014 at 21:39

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