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New siding/windows and rigid insulation – need some advice

Gadg8man | Posted in General Questions on

We have a 46 year old house that we have renovated extensively inside and are now planning a major exterior renovation for the spring. We live in Newfoundland, Canada and are in Zone 6.
We are removing the siding and windows and I want to upgrade the exterior insulation while we are doing the job. Currently we have aluminum siding over 1.5″ foam sheathing which is connected directly to the 2X4 studs. There is diagonal bracing in place. There is new fiberglass batts with 6 mil poly and drywall on the main floor, however, the second floor has original fiberglass insulation and minimal Vapour barier.

We live In a very windy environment, one of the things I would like to do is add 1/2″ OSB over the existing rigid insulation screwed to the studs, for extra rigidity, then add another 1″ of rigid insulation over the OSB. Would this be a problem? Basically I would glue the OSB to the existing foam fist, then glue the new rigid to the OSB, therefore forming a solid SIP style sturucture. I would then cover the outside insulation with Tyvek and install strapping for the new siding.

Finally I would install a rain screen at the bottom to allow any moisture to escape the wall system.

I am looking for comments and suggestions.



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  1. GBA Editor
    Martin Holladay | | #1

    Your idea would probably work, but it sounds laborious.

    Why not buy some nailbase (rigid foam with OSB facing on one side)? If I were installing a layer of nailbase on your walls, I would probably install it foam side in -- foam-to-foam, so to speak, with the OSB layer facing the exterior. Then install housewrap, furring strips, and new siding.

  2. Gadg8man | | #2

    Thank you.
    I will have a look for that product, I haven't seen it before.

  3. GBA Editor

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