I am working on a 1970 Coastal California redwood home built in central Vermont
user-6712296
| Posted in Energy Efficiency and Durability on
I am working on a 1970 Coastal California redwood home built in central Vermont. It has cathedral ceilings with T-and-G black willow nailed directly to the rafters. It doesn’t have amazing insulation. Would it make sense to install R10 foam board?
Are there other ways to tighten the envelope without removing the planking or sheathing?
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Replies
User-671etc.,
First, can you tell us your name?
I'm not sure what the definition of a "coastal California redwood home" is, but I think I get the picture. You're basically describing a cathedral ceiling with poor insulation or no insulation, as well as no air barrier, that has been finished on the interior with leaky tongue-and-groove boards.
Q. "Are there other ways to tighten the envelope without removing the planking or sheathing?"
A. Yes. The best solution in this case would be to install an adequate thickness of rigid foam on the exterior side of the roof sheathing. This would require the existing roofing to be removed. After the rigid foam is installed, you would have to install a second layer of roof sheathing and new roofing.
If you go this route, it would probably be best to fill the rafter bays with dense-packed cellulose (working from above, by drilling holes through the roof sheathing) before you install the rigid foam.
For more information, see these two articles:
How to Build an Insulated Cathedral Ceiling
How to Install Rigid Foam On Top of Roof Sheathing