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Last Updated: , Created: Thursday, September 14th, 2000

Insulating the roof above an attic knee wall

Scott from Elmwood Ontario wanted to know how to get insulation into the small space between the drywall and the roof in a renovated attic -- that slanted part of the ceiling above the knee wall -- and still leave space for ventilation.

My trick is to put little or no insulation between the roof members, to make sure that there is a vent space. Then I put 2 inches or more of Styrofoam OVER the roof members on the inside, the same way that the drywall goes on. Drywall over that. That gives you a minimum of R-10, which isn't much, but is a most effective R-10 because it covers all the structural members. You don't get cold pieces of wood going through the insulation, no thermal bridges. Actually you can put a fair amount of Styrofoam here because the slant saves you head room, and the surface isn't so large as to be too expensive. You could use or not use the Styrofoam on the kneewalls and the ceiling, depending on how much Fiberglas you manage to get on the other side of these surfaces.

Keywords: Cathedral Ceiling, Attic, Insulation, Ventilation

Article 608