Quote:
Originally Posted by dablack
So I just picked up 17k sqft of foam board insulation...
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There is a website called
Building Science that has some wonderful information on what you are doing.
Regarding attachment, long stainless steel screws with the plastic equivalent to fender washers would be just great.
Regarding tape, duct tape will not hold up. You will need a tape that is designed for the job and it will not be inexpensive.There are a lot of emerging products that will help. Fine Homebuilding magazine did a great comparison a few issues back, look at their site, go to your public library.
The structure that you intend to put over the insulation layer is called a "Rain Screen". If you Google that you will see much good info. The idea is to build it so that you will have abundant bug-proof air flow behind, so that if rain comes in gusts, there is a pressure equivalence and the rain itself is not driven through the screen, and any minor droplets can run down the water-resistant layer that is behind the siding, behind the air gap.
It's a fairly new concept, but it has been well tested.
By the way, I have used loads of the insulation board, and 3/4" would have the following R-value, depending on the type you bought:
White EPS = R-3.2
Pink or Blue XPS = R-3.75
Yellow Polyiso = R-4.9
The big benefits from what you are doing will be primarily a big reduction in air infiltration, secondarily reducing 'thermal bridging', and lastly increasing the overall R-value of the walls.
Be sure to prime the back side of your siding material.
Good luck on your project!!
Best,
-AC