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-   -   2" foam or Foil Back? (http://www.diychatroom.com/f103/2-foam-foil-back-133937/)

hellothere123 02-16-2012 10:37 AM

2" foam or Foil Back?
 
I have 2 options:
1) 3/8" Foil Back Styrofoam (R5) overtop of existing x90 - without removing x90 for $1700.00
2) Remove x90, housewrap, 2" styrofoam insulation (R10) for $4200.00

I live in Canada


I'm not sure aboout option 1...if you put the r5 overtop of the x90, I think there would be a ton of air gaps as it is lap siding...but how much do you really gain with the r10 and vinyl siding vs r5 + the r value you'd have from your existing x90?

Your thoughts?:wink:

AGWhitehouse 02-16-2012 10:40 AM

2"@R-10 is XPS and at that thickness is considered a class II vapor retarder. The foil facing is likely considered a class I vapor retarder. Best to make sure you're not creating a double vapor barrier system and create the "Sick building syndrome". The walls need to breath...

Windows on Wash 02-16-2012 02:36 PM

Quote:

Originally Posted by AGWhitehouse (Post 854988)
2"@R-10 is XPS and at that thickness is considered a class II vapor retarder. The foil facing is likely considered a class I vapor retarder. Best to make sure you're not creating a double vapor barrier system and create the "Sick building syndrome". The walls need to breath...

+1

Foil facing is going to make it Class I in about 99% of the cases.

Be careful of that moisture trap.

hellothere123 02-16-2012 05:20 PM

I'm sorry...I don't know what you are trying to say...dumb it down for me a bunch!


Thanks!

hellothere123 02-17-2012 11:13 AM

anything further? :huh:

Gary in WA 02-17-2012 02:42 PM

Please ask the identical question in one forum, not multiple areas, thank you.

Gary

Gary in WA 02-17-2012 02:46 PM

1. How thick are the walls?

2. Is there poly vapor barrier inside? Hence the concern of a faced foamboard outside and poly inside. Unfaced XPS foamboard (2") exterior and poly inside will work if the inside air leaks are stopped.

3. Where in Canada are you located (to find your insulation requirements)?

Gary

hellothere123 02-17-2012 08:45 PM

Quote:

Originally Posted by GBR in WA (Post 855913)
1. How thick are the walls?

2. Is there poly vapor barrier inside? Hence the concern of a faced foamboard outside and poly inside. Unfaced XPS foamboard (2") exterior and poly inside will work if the inside air leaks are stopped.

3. Where in Canada are you located (to find your insulation requirements)?

Gary

Sorry :wink:

2x4 walls
vapor barrier is installed on inside
Saskatchewan

I think it should be alright...everyone around here does that..some even go with a R12 insulation on the outside

I'm not totally sold on the benefits vs cost of doing this...

Funny thing is some people will put the 2" foam insulation ontheir house but won't replace the windows until they have the money...I think windows are the biggest loser in terms of losing heat / cold for your house..I dunno

Gary in WA 02-17-2012 11:32 PM

Compare the square footage of walls to windows. If older R-9 f.g. batts with air movement, you need the added insulation for your climate. 2" f.b. is fine without facing as I said earlier. No vapor problems: http://docs.google.com/viewer?a=v&q=...4EyM707m0gPdXQ

Cruise around here: http://oee.nrcan.gc.ca/publications/residential/8584

Drain your cladding; http://www.buildingscience.com/docum..._enclosure.pdf

Gary

hellothere123 02-18-2012 06:13 PM

Thanks..I'll read up :thumbup:

Chemist1961 02-19-2012 07:51 PM

do it right
 
I sided a house in Regina in 1976 with X90. Why not strip down in the spring and do it right. For the money you will spend you can probably pay a couple of kids $100 each and dig in. For the improved level surface it will likely pay you back in a proper seal and fight off those COLD winters!!!!At least if you strip it you can use up to date material and inspect the whole structure, seal your windows, etc.


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