Batts for rough-cut 2x4s?
dbaerg
| Posted in Green Products and Materials on
I have a client that is gutting a house built in 1920. There is loose fill fiberglass between the rough cut 2×4 studs. If she replaces these with batts, the commonly available 3.5″ rock wool or fiberglass batts will only partially fill the cavities. Does anybody sell a full 4″ batt? Or is there some way this could be done properly? If she scrunches a 5.5.” batt into the cavity what R value could she expect from the compressed batt? Is it likely to cause problems with the drywall?
Thank you,
David Baerg
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Replies
You don't want a void, so it is better to compress a thicker batt. See this table (http://www2.owenscorning.com/literature/pdfs/10017857%20Building%20Insul%20Compressed%20R-Value%20Chart%20Tech%20Bulletin.pdf), which I saw referenced in a post in Allison Bailes' blog (https://www.energyvanguard.com/blog/compressed-fiberglass-insulation-really-so-bad).
The post was prompted by a comment from Dana Dorsett on GBA.
David,
Steve is right. Purchase 5.5-inch batts and compress them. You'll get a higher R-value per inch with a compressed batt than an uncompressed batt.
You might end up with R-4 or even R-4.2 per inch -- in other words, R-16 to R-16.8.
.
I've faced this problem many times. Use the 2x6 batt. It will fit fine and it won't hamper hanging drywall.
It is so rare for batts to be installed well even in modern framing. If you can every wall open at the same time wet sprayed cellulose insulation will give you a better fill for similar cost.
Walta