Insulating New Addition


Old 09-11-03, 09:24 AM
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Join Date: Jan 2002
Location: North Reading, MA
Posts: 136
Insulating New Addition

We just had a 10x24 addition to the kitchen. This was built over what used to be a deck, so dirt sits below. Because the yard slopes down a bit, there is is about 2ft to 3ft of height between the floor of the new addition and the ground below. The addition sits on pressure treated posts, and the space between the posts was blocked with Durock on two sides to keep animals out, and lattice on a third side, providing some free-flow of air; the fourth side is the original house foundation.

This being said, what kind of insulation do I put between the joists on the underside of the floor? Unfaced batts? Kraft-faced batts? If so, which direction does the paper face? What R-rating is appropriate, at a minimim? R-19?

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Old 09-11-03, 02:04 PM
Ed Imeduc's Avatar
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389

We put a 4 mil poly over the floor joist and then put down the floor over them for a good V/B. But thats over and cant do it anymore. So I would say put R19 up in the joist paper side up to the floor If it would fit a R30 would be 8 1/4". Id put up a1/2"X 1/2" mesh over the bottom of the joist to keep things out of it. an just let the 3 walls as open as can be more lattice on another wall would help. ED
Old 12-06-04, 06:21 AM
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Double vapour barrier??

From what I have read on this site, paper backed insulation (according to most people) is a vapour barrier, so by adding the poly on top wouldn't this just trap any moistire that happens to get through the poly on top of the Kraft??

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