Thin radiant barrier insulation on siding replacement?
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For a brick facade house with masonite siding that needs to be replaced (brick front, siding other three sides), an opportunity to install continuous exterior insulation presents itself. Problem is, no overhangs on the gable ends. Is a reasonable solution to use a product such as:
http://www.insulationstop.com/radiant-barrier-foil-insulation-double-bubble-square-edge-48×100.html
or similar (the radiant resistance, and an R-value of 8+)? With existing house wrap (likely, hopefully) would you need to count on the new insulation barrier to be sealed (taped)? Obviously, the masonite was not installed with furring strips to create air space, so is it worth it, then, to consider adding overhangs to the roof system in order to allow space for an air gap between insulation and new siding?
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Replies
Bradley,
The manufacturer you linked to, like almost all manufacturers of foil-faced bubble wrap, is lying. These products have an R-value that ranges from R-1.2 to (at most) R-2. For all intents and purposes, they are worthless.
I have reported many of these manufacturers to the FTC for violations of the federal R-Value Rule. Occasionally, the FTC sends out warning letters. But then the exaggerations resume.
If you want insulation, buy some real insulation: either rigid foam or mineral wool.
10-4. The problem is the projection of the "real" insulation. I'm not trying to dumb down a solution, I'm just trying to find out if there is a reasonable middle ground, and is it worth it. Is making a small difference, with relative ease, over a large surface area worth it? It is only three sides, but if it's R-13 in walls (which is actually 7-9 pending quality...tell me about R-Value Rules!), adding 2 to it is half as much as one inch XPS, and increases the assembly R-Value by maybe 25%. Seems pretty clear where you stand, which is helpful. With this additional commentary (and added photo), am I wasting my time? Adding overhangs is another obstacle...
Bradley,
A competent carpenter should be able to pack out your rake trim, and a good sheet-metal contractor can bend up some rake flashing that will project past the packed-out rake trim. A few inches here, a few inches there, and you're all set.
Of course. Just trying to find a place between "all" and "nothing". Once you start to add that thickness, you run into more and more necessary changes down the line, and the $0 option starts to look a whole lot more tempting than the $10,000 number. What the $0 allows them, though, is a chance to save for the $10k without having to throw out a $3-4k job when the time comes.