Quote:
Originally Posted by S-F
I hear ya on any improvement being good. The point I was trying to make is that for the same money you could ADD R20 to your whole house, almost completely eliminate thermal bridging and not disturb the living space much at all with outsulating the walls. You also can add a rain screen which is great. Of course to really do it right you would need to tear up the inside of the house. I plan to add foam to the outside and then probably do something like a mooney or double wall on the inside when time permits.
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Hi,
For the regular Mooney wall, the R value improvement would be R3.7 per inch times 1.5 inches is +R5.6. Plus essentially eliminating thermal bridging. You could also go with wider than the 1.5 inch strapping and get more R value.
And dense packed cellulose is a good air sealer -- this could be important on retrofits where its harder to good air sealing after the fact.
If you look at the cost numbers for the Mooney wall example here:
Mooney Wall -- A low cost, high R value wall
and, you take out the cellulose that fills the 2 by 4 part of the wall, then the cost per sqft is about $1071 - ($843)(1.5/5) = $818, or 39 cents a sqft. This includes the cellulose in the 1.5 added inches, the 2 by 2 strapping, glue, and insulweb stuff.
Adding R20 XPS would be about $2.10 a sqft plus a ton of fairly expensive washer screws to hold it down, PU sealing foam, and all the hassle and expense of extending the window and door frames out for the 2 inches -- a pretty big job. It also seems like its pretty much something you have to do when its time to replace your siding -- I don't see how you could put the old siding back on?
Not saying either method is best, but I think the Mooney Wall has its place -- it kind of depends on your situation and what kind of exterior finish you have on the house.
Gary