# exterior XPS



## Fix'n it (Mar 12, 2012)

i am going to be siding the back of my house kinda soon. just vinyl (cost).
i was told, in a thread i cannot find now, that i can just go over my current siding. which is asphalt and in servicable condition. i was told to just use fanfoil. but i want some insulation factor. so, can i just go over it. and, is 1" xps good for this ? or what ? what else do you need to knoww ?


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## cleveman (Dec 17, 2011)

If I'm re-siding something, say something sided with the old clapboards or the lousy press-board, I like to remove this siding, deal with any doors and windows, then wrap the house properly and re-side. If you would like to add some xps, then I would suggest 1" tongue & groove.


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## Windows on Wash (Aug 30, 2011)

I would pull everything off, seal all the gaps and cracks, re-tape the nailiing flanges, install some T&G XPS (depth depends on your wall depth and climate), Tyvek/Housewrap, and new siding. 

Be sure to include drip caps and rigid flashing details.


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## HomeSealed (Jan 3, 2008)

Good advice above... The best way is to tear it all off and then add the insulation board to the thickness of your choice. If you are set on not tearing it off, stick to the fanfold.
What do you have in your wall cavities for insulation?


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## chemman (Apr 2, 2012)

Isn't housewrap overkill if you already have XPS on the exterior?:huh:


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## Fix'n it (Mar 12, 2012)

ok, i figured you guys would say that. i am guessing it would come off somewhat easily. though a mess.

inside my walls. 2x4's with 1" furring added = 4 1/2 depth. . 1" xps caulked to seal it in cavity. then roxul. 


i was planning 1" xps outside.


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## Fix'n it (Mar 12, 2012)

chemman said:


> Isn't housewrap overkill if you already have XPS on the exterior?:huh:


i was thinking the same thing.


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## HomeSealed (Jan 3, 2008)

chemman said:


> Isn't housewrap overkill if you already have XPS on the exterior?:huh:


Not if you want a proper drainage plane/ lapping of flashing etc. Yes, taping of the seams can be effective, but I prefer a proper wrb for long term performance around the window and door openings.


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## Windows on Wash (Aug 30, 2011)

Big +1 there.


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## HomeSealed (Jan 3, 2008)

Here is an example of why the wrb is still important. This home had an active water into the wall cavity.


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## HomeSealed (Jan 3, 2008)

Since when can you not edit posts after 30 min? Weird...
Anyway, just wanted to add that in this particular situation, the seal of the head flashing to the xps failed introducing water into the wall cavity, and then someone installed replacement windows and capped over the original head flashing, introducing a second source of moisture. This one needed some sheetrock repair due to water damage.


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## Windows on Wash (Aug 30, 2011)

HomeSealed said:


> Here is an example of why the wrb is still important. This home had an active water into the wall cavity.


Where is your finger?


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## DuPontTyvek (Jul 23, 2013)

This is Cathy from DuPont. It’s a good idea to use a weather barrier with XPS or other exterior foam insulation. We recommend DuPont™ Tyvek® HomeWrap® on top of the foam or Tyvek® DrainWrap™ for enhanced drainage when installed under the foam. Also, DuPont does not recommend taping the foam seams regardless of whether the Tyvek® is installed under or over the foam. Not taping the seams will have very little effect on the foam’s R-value, and because of the low permeability of the foam, the open seams will help the wall breathe.


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