Double 2×4 wall
faiakbuilder
| Posted in General Questions on
I am building a house and have a question about wall design. I would like to build the exterior walls with 2×4 @ 24” o’clock filled with closed cell spray foam. Then 2” of rigid foam on the inside then 2×4 wall on the inside to run the electrical and attach the drywall. Any issues or comments?
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Replies
Faiak,
There are literally scores of variations on double-stud walls, and a lot of the variations depend on factors such as whether the house is one or two stories, or which wall is load-bearing.
My suggestion would be to look through a number of the ones that have been featured here on GBA, or do a Google Image search, and draw a wall section from foundation to roof which will identify which strategies you are thinking of using. That will elicit much more useful comments from the readers here.
Also calculate $/R and check for code compliance.
Faiak,
I'll echo Malcolm's comment. Here is a link to the Category page on walls -- with links to lots of relevant articles: Category page on Walls.
Geneally, I'd say your approach could work, but it's unnecessarily expensive, and depending on the foam choice, entails unnecessary greenhouse gas emissions. If you've spend the money on the double stud wall, you can get more insulation for less money if you use one of the other approaches described in the links from the page Martin linked.
I’m usually a fan of spray foam, but not in this application. There are better/cheaper/greener ways to do it. At the very least, consider using open cell instead of closed cell spray foam here. Closed cell won’t usually be applied to “fill” a wall cavity due to the difficulty trimming it flush, so you’d end up with an air gap which is bad in your application. Closed cell foam also uses much more material per R than open cell, and gains you nearly nothing due to the thermal bridging of the studs.
There are many ways to build a wall. Lots of articles here to read and learn. There are also different pros and cons to different assemblies, and differing preferences between individual builders too. My own preference is for thick exterior foam, mineral wool in the wall cavities, and not a double stud wall, for example.
Bill