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Mary Ann Survan · Apr 23, 2009, 05:07 AM

How do you insulate a cathedral ceiling with no attic?

Perito · Apr 23, 2009, 05:27 AM

There is always a space between the ceiling and the roof. Sometimes you can cut a hole in the top of a closet and get into the attic, but it can be difficult because the clearance may not be enough for a human body to get through.

The usual way to insulate this type of attic is to do it when replacing the roof. The sheathing that goes beneath the shingles is removed and insulation is blown in or rolled in.

creahands · Apr 23, 2009, 06:21 AM

Hi Mary Ann

Is the house finished inside and out?

Blown in insulation can be put in by opening top of roof. The problem with blown insulation is that over time it settles and will leave a void at top.

Foam insulation would be another way to go. This does not settle.

This is not a DIY project.

If unfinished inside can use bat insulation with ladders or scaffolding.

Good luck

Chuck

ballengerb1 · Apr 23, 2009, 07:45 AM

It really depends on how the roof was built. I have worked on maybe log cabins where the inside roof was the underside of the exterior decking. Not a good insulation but years ago fuel wasn't that expensive so corners were cut. You need to tell us the thickness and makeup of each layer of the roof. In the extreme situation I just described we glued 2" rigid foam to the ceiling and then covered that with tongue and grove carsiding.

21boat · Apr 25, 2009, 08:24 AM

Spray foam is the best for R value and no voids for moisture to hide in.

fishingbuddy55 · Jul 22, 2012, 06:48 AM

roof consist of 2x6 rafters with 2x4 slats and a tin roof

SpringtimeHomes · Jul 25, 2012, 08:45 AM

This can be tricky especially if your goals include saving on energy costs. Foam board sheathing is your best bet as it will slow the energy flow through the rafters which can be quite significant.

Check out this article on Creating a conditioned attic and be sure to check out the link insulating cathedral ceilings

jefferson17 · Oct 18, 2012, 10:08 PM

+1 on foam board sheathing. Install between roof joists, foil facing heated area. 2" thick.

cyrilla · Aug 15, 2013, 11:38 AM

Hello - I too have a 60 year plus cottage A Frame two story so it is basically the walls and roof equivalent that I need to insulate with 2 inch rigid foam.
The exterior roof has been reroofed with felt and asphalt certainteed lifetime shingles. On the inside, we'd like to use 2 inch rigid foam as you described.
The exposed beams are now 5 1/2 inches. What type of glue did you use to hold the foam? It would appear that you did not leave air pocket since you glued directly to the under side of the exterior plywood? How then did you nail the car siding?