XPS or foil IPS basement wall
I had a post a couple weeks ago, with your guidance it was determined I needed a minimum of R5 & then my fiberglass faced insulation in my Climate Zone 5, interior side of a basement that is 7′ 6″ below grade and 6″ above grade basically.
Currently the only way to achieve R5 foam insulation is with 1″ of XPS or 1″ of foil faced polyiso. I want to stay as thin as possible but meet the required r value to prevent issues. If I use the double foil faced poly iso @ 1″ and frame out 2×4 walls and use r-13 fiberglass batts with kraft facing, I should be able to achieve the most cost effective option.
However the supply of 1″ polyiso may be a bit short so I was wondering about the idea of using it and then if I run out, switching to DOW 1″ XPS to stay the same thickness? I like the foil faced stuff because it is cheaper and looks like it will be easier to glue against the foundation wall, and also much easier to use tape on (foil tape on foil facer) and lastly, looks like it won’t be as messy to cut as the blueboard.
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Replies
Ralph,
Martin's basement article (https://www.greenbuildingadvisor.com/article/how-to-insulate-a-basement-wall), citing the 2012 Code for Zone 5, advuses R-15. How did you arrive at R-5?
Also... Have you considered using reclaimed foam on your project? Reclaimed foam is cheaper and greener than new product.
In my earlier question I was told I would need R-5 Minimum before using the R-13 fiberglass in a 2x4 stud wall.
You can use XPS here instead of polyiso when you run out of polyiso. Either type of insulation will work in this application as long as you use thick enough material to reach the R value you need.
You should look into reclaimed foam here too. Reclaimed foam is a great choice in applications like this where it will be hidden from view.
Bill