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Due to aesthetics, R-20 (4 1/2 inches of rigid foam) above the roof is my limit

Due to aesthetics, R-20 (4 1/2 inches of rigid foam) above the roof is my limit. Would Roxul plus an airspace in the rafter bays be a good choice for the remainder of the needed R-value?

Jesse, 80% of home is concrete slab with remaining 20% being crawl space I closed in - conditioned basement. In a high water table area with no vapor barrier under slab or crawl. De-humidifier runs constantly.

I plan to include air space in rafter bays under sheathing along with batt insulation for remainder of needed R-value. Is an airspace necessary with R-20 foam above roof sheathing?

Asked by cameron morris
Posted Tue, 07/01/2014 - 08:31
Edited Tue, 07/01/2014 - 09:34

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Cameron,
It looks like you intended to post this on a different page. In most cases, it makes sense to maintain just one thread for a series of questions, rather than starting a new thread each time.

Here is a link to the original thread:
http://www.greenbuildingadvisor.com/community/forum/green-building-techn...

It would be a good idea to post all answers back on that page.

Answered by Martin Holladay, GBA Advisor
Posted Tue, 07/01/2014 - 09:36

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