Whether it’s worth removing Sheetrock in closets to spray foam
yzerham19
| Posted in General Questions on
Dear all, I have a Cape Cod and plan on insulating the second floor by air sealing with 2 inches of spray foam and then finishing with 3.5 inches of Ultra Touch cotton batts to fill the 6 inch rafters.
There are a few closets that are sheetrocked and will take a great effort to remove. Since the closets have doors thus preventing most of warm air to condense against the roof after dense packing with cellulose should I have any concerns? Ideally I would like to air seal whole of second floor but ripping out all the Sheetrock is a large task.
Mike
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Mike,
I'm sorry to be the bearer of bad news, but here it is: it's time to demolish the drywall in your closets.
It sounds like you have decided to use the flash-and-batt approach to insulate your sloped roof assembly. If you do this, you will end up with an unvented cathedral ceiling. I suggest that you read the following article: How to Build an Insulated Cathedral Ceiling.
Your two inches of spray foam will provide an R-value of about R-13. That is adequate in Climate Zones 1, 2, and 3, as well as Zone 4C. However, in Zone 4A, 4B, or anywhere colder, you will need more spray foam. The details are in the article I linked to.
Thanks for your feedback Martin. I read the article and gained more insight. I am in zone 4a so my flash and batt option will yield r-26. I figure this should suffice until I add rigid board when I replace my roof in the future. Right now I close off the attic which is unused using a weatherstripped door so no heat from downstairs will seep to the roof and condense against the roof. Before I did this I had ice dams but not since. I just figured that sealing the closet doors and dense packing the closet ceilings would be better than the current setup hus averting condensation enough to avoid major damage until I redo the roof and add rigid foam board which will ultimately solidify everything. I know the theory behind why closed cell should be used on the roof to air seal but also comparing with what I have now and feel that logically it should be fine.