Insulate exterior walls

17 years ago

I am purchasing a new house, well it isn't new, but... In the addition, they just put the paneling right over the studs, so i am going to remove the paneling, and add drywall. I am also going to add 2 inches to the exterior studs to make the wall a 2x6 instead of the 2x4. I am trying to decide the best way to insulate. I know the best is probably a spray insulation, but I will be in a small town where a contractor would have to drive 70-100 miles just to do the work, and from past experiences, that can double their price.

I am considering using unfaced fiberglass and than cover with 6 mil plastic, or adding 2 inch xps and then 3.5 of fiberglass.

Because the 2 inch xps can be considered a VB, should I first apply the 3.5 inch of fiberglass, then the xps, and tape and caulk all seems? I am leaning more towards this method because it will give me a higher R rating, and I think it will help more with air leaks.

But your thoughts, or other suggestions would be appreciated, thanks,

Michael

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Comments (6)

pjb999
17 years ago
You can buy a sprayfoam kit online, and do it yourself.
Michael Baldwin
Original Author
17 years ago
Any recommendations of DIY spray foam kits?
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drywall_diy_guy
17 years ago
I have done exactly as you plan to do on 2/3 of my house now. I used a combination of 6" unfaced batts, 2" dense foam over headers, and expanding foam in tight spots. I then put a plastic moisture barrier over the top before drywalling. See the website below for details on how to do this.

Here is a link that might be useful: Make Walls Thicker
manhattan42
17 years ago
You do not provide enougn information to even begin to remotely help you.

We need to know the state( or province) and county in which you live to determine what insulation you should have.

Without which, anyone's suggestion's have no merit whatsoever...

Please tell us and we may get somewhere...
drywall_diy_guy
17 years ago
I forgot to address you vapor barrier question.
Yes, put the fiberglass batts in first, and then the dense foam. And put a plastic vapor barrier over the top of all that. You don't want that moisture getting trapped between vapor barrier layers in the fiberglass. Personally, I think your best bet is to simply use 6" batts in the deep cavities and dense foam over headers. Or better yet, if you can afford, have insulating foam sprayed in.

Many years back a local builder in our area had a mistaken idea that he should put a plastic vapor barrier on the exterior of the house. The result was moisture trapped and homes that needed to be torn down. The vapor barrier role is to prevent/reduce moisture from building up inside the walls.
Michael Baldwin
Original Author
17 years ago
drywall_diy_guy,
Thanks, that was helpful on the procedure for the project. I to will be replacing a few windows, and adding more, this addition just does not have enough natural light. I would rather go with spray foam, but it is costly, well not as bad as i thought, I talked to an Icynene installer, and the price for him to do it is about what I would pay to use Tiger Foam myself. I think tiger Foam has almost twice the R value of Icynene though. But with Tiger Foam, I don't need to Fer the walls out to 2x6, I will have R 20 plus in the 2x4 wall space. this is such a pain to decide what to do.

manhattan42,
I live, well, will be living in the central part of NE, where they recommend R19 in the walls, from at least what I can find out.

Thanks,
Michael