Insulating a shed roof that is difficult/impossible to vent
Ekstrom
| Posted in Green Building Techniques on
Hello,
I have shed roof dormer that ties into the roof below the ridge line, so venting is a challenge. The shed dormer is currently under-insulated with a vent for air to enter, but not to exit, and I have moisture issues inside. I’m in New Hampshire at 1200ft above sea level (climate zone 6a, I believe).
My question: If I re-insulate my roof and bring it to R49, will I solve moisture issues due to inadequate venting?
Thank you,
Rodney
New Hampshire
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Replies
Rodney,
It's perfectly possible to create an unvented insulated roof assembly. To do so, you need either: (a) to install at least a portion of the insulation as rigid foam above the roof sheathing, or (b) to install at least a portion of the installation as closed-cell spray foam below the roof sheathing.
There are rules dictating the minimum required R-value for these foam layers. All of the rules and other details are explained in this article: How to Build an Insulated Cathedral Ceiling.
Thanks, Martin.
The article you referenced is very helpful. Appreciate the quick reply.