"R-30C" insulation


Old 04-13-05, 07:32 PM
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Question "R-30C" insulation

Anyone have thoughts on the use of this product? The manufacturer claims that it has the same effectiveness as regular R-30 but can be installed in a 7 1/4" space instead of 9 1/4" as in a 2x10 joist. The R-30C batt is supposed to have more fibreglas in it than a regular R-30 batt.

I always thought it was bad to compress fibreglas to make it fit in a smaller space because that would reduce the R value. But it looks as if this is exactly what this product does. If that's the case then why don't I buy R-30 and just scrunch it into the 2x8 joist spaces?

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Old 04-14-05, 02:39 AM
Join Date: Mar 2005
Location: Chesapeake, VA
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Sounds great if it works! How's it priced compared to standard fiberglass?There are other insulations out there with very high R-values in a small size; some will give R-30 in as little as 4".
Old 04-14-05, 09:38 AM
Join Date: Nov 2001
Location: USA
Posts: 1,873
American Society for Testing and Materials (ASTM), is the method that manufacturers use to rate R-value of their products. So regardless of the thickness of the product the method in which the products are tested remain the same. If the product is used other than what it was intended for then the rating does not apply. For example, if you compress the insulations into the cavity, then you would not have the same R-value for either insulation.

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