DIY Home Improvement Forum banner
1 - 5 of 5 Posts

·
Registered
Joined
·
355 Posts
Discussion Starter · #1 ·
I planning an addition to my house and am starting to think about insulation. Based on my reading of the local code, the exterior walls need to be insulated at r-18 value. As this is an addition and we have relatively limited space, I had been planning on building it out of 2x4, but using batt insulation, I believe I would be limited to r-15, no? So, any thoughts on what I can do?

So far as I can tell, my options are:

1) Frame using 2x6 - This is not a preferred option because space is so limited. Even 2" will make a difference.

2) Install r-15 batt insulation in the stud cavity and a layer of r-5 foam board insulation on the exterior, for an r-value of 20

3) Install spray foam insulation in the stud cavity, 3" thick for an r-value of 21.

4) I have read of some people doing a 1" spray of foam insulation in the stud cavity and then installing batt insulation on top of that. Any experience with this method? Would you have to compress the batt insulation?

Any other thoughts? What's your preference?

Thanks!
 

·
Remodeling Contractor
Joined
·
3,590 Posts
2 X 6 walls or spray with closed-cell is the only way to go. 2 X 4 with batt insulation is R-13 only. Using a 1" spray and then R-13 will still not give you what the code requires. And code requirements are minimums. More is better. 2 X 6 walls are the way to go.
 

·
Registered
Joined
·
355 Posts
Discussion Starter · #3 ·
Thanks Bob.

For what it's worth, Owens Corning, and a couple of other companies, now have high density fiberglass batt insulation that allows for r-15 in a 2x4 wall and even r-21 in a 2x6.

That said, I am seriously considering how to make the 2x6 walls work. The room is just very narrow and I am trying to loose as little space as possible.

Any other suggestions?

Thanks!
 
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top