Best type of batt insulation in encapsulated crawl
StevenNC8b
| Posted in General Questions on
Which is preferred in stud walls when encapsulating a crawlspace. I believe spray foam is out of my budget. The two types of bats available at my local big box store are fiberglass or Rockwool. Is there advantage of using one over the other? The cost difference isn’t huge.
Thanks
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Replies
Steven,
Unfortunately, you need to use an impermeable insulation like foam board to stop the warm crawlspace air condescending on the cold concrete. If you use batts - either mineral wool or fiberglass - you risk mold and moisture problems. The foam board should be detailed to be air-tight, by sealing the perimeter and joints between sheets.
Hey thanks for the reply but... That doesn't line up with what I was told in the other post when I asked about encapsulating wood framed crawlspace walls. Do you mean foam on the concrete walls or all of them?
Thanks again
Steven,
Apologies - I completely missed you were asking about the stud wall cavities - which is hard to understand when it is there in black and white in your first sentence.
If the price difference is not too large, I would go with Rockwool. It's easier to do a good job filling the cavities, is more resistant to moisture damage if it ever gets wet, and less susceptible to convective air currents than fiberglass.
That said, fiberglass is perfectly fine too.
I've read that fiberglass batt insulation will lose its insulating value when it gets wet.
https://www.thermaseallakeside.com/blog/what-to-do-when-your-insulation-gets-wet/#:~:text=Every%20type%20of%20insulation%20will,can%20start%20to%20grow%20mold.
Here's a video from Architect Steve Baczek on basement wall construction and insulation. It includes spraying 2" of closed cell foam on the concrete but he explains why it's the best and often cheapest option.
https://www.youtube.com/watch?v=on-e6lUBGyE