Insulative Sheathing Help

Insulating existing homes to maximize comfort and energy efficiency.

Insulative Sheathing Help

Postby dubb151 » Wed Dec 29, 2010 9:11 pm

I have a 70's era home with "batt and board" wood siding, 2x4 structural walls. We would like to re-side the house this summer and put in new windows, old ones are wood, single pane. We would like to take advantage and improve our efficiency while doing this project, seeing as there is only R-11 kraft-faced fiberglass in the walls. I am thinking about just pulling off the wood batts, leaving the painted plywood, adding insulative foam board and then siding over. There is tar paper between the plywood and sheating. What steps are necessary and materials needed to carry this out? Is it even a smart way to do it? I am a electrician and a competent carpenter, but I am not experienced with this sort of retrofit. I would appreciate any tips or help so I don't screw up by assuming I know what I'm doing. Thanks.
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Joined: Wed Dec 29, 2010 9:09 pm

Re: Insulative Sheathing Help

Postby Larry » Wed Jan 12, 2011 9:30 pm

Hello: A lot depends on your climate and ultimately where the dew point can get to in your walls. Generally though, moving from the existing wall outwards; start with the existing plywood, then rigid foam, then a waterproof barrier, then vertical battens installed with long screws to the existing studs, then Hardiplank or similar rot-proof siding fastened to the battens. This gives you a drainage plane behind the siding to keep liquid water away and hopefully puts the dew-point inside of the foam, where it can do no harm. I'd put the windows towards the outer plane of the wall because it's so much easier to make them waterproof and you get the benefit of a large interior sill for curious cats.

There are completely different ways of going, using cellulose or other insulation materials... as I'm sure you'll discover ;)

Two other web sites you might want to have a look at. and Some of the best building scientists run or frequent these sites.

Yours, Larry
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Joined: Sat Jun 05, 2010 12:19 pm

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