Technical > Home Improvement > Insulating Behind Studs

reply to ropeguru

Re: Insulating Behind Studs

reply to QuaffAPint
Some observations.

OP is in PA. In that climate zone he needs a vapour barrier - a meaning just one and only one.

So, how does he get just one vapour barrier?
Either install a 6 mil poly barrier, sealed & taped, right under the drywall - or by utilizing 2lb. polyurethane spray foam.

But like most jobs , we want to get the most bang for the buck given the tradeoffs we have to make.
Since the wall is below grade and we have no real idea how well water proofed the exterior of the basement wall is, we have to assume that it isn't and that some moisture will permeate through the foundation.

So how do we best handle that, and insulate the wall so there is only one vapour barrier, and keep costs down?
Apply 2lb. polyurethane spray foam to the concrete in thin layers until it reaches the backside of the studs. This will resist the infiltration of water vapour through the concrete into the wall cavity. Then fill the stud cavity with batt insulation - your choice of fiberglass or mineral wool (Roxul). I'd choose Roxul for its fire suppressing and sound control properties vs. fiberglass.

Then apply the drywall directly over the studs WITHOUT a poly vapour barrier. Why? Because the wall has to dry to one side if, as, and when moisture gets trapped. Even painted drywall is still permeable to moisture, so if you have a polyurethane foam vapour barrier on the concrete then you MUST leave the opposite side of the wall cavity able to "breathe" in order to dry the wall assembly out when moisture gets in, hence only painted drywall is needed.

The sole plate will also absorb small amounts of moisture from the concrete floor if there is no foam gasket under the sole plate.

If you have one vapour barrier on each side of the wall assembly (ie. foam & poly) then you set the stage for mold growth inside the wall cavity.

Also use spray foam to insulate the band joist area between the joists above the foundation wall, minimum 2" thick, then add at least 4"-6" of Roxul on top of that (so the combination yields R24 or more). The band joist area is always a source of air leaks and heat loss which the foam & batts will solve.

»Re: Insulating Behind Studs

reply to QuaffAPint
Guys, MaynardKrebs' recommendations on this matter (Insulation and all related matters) is as rock solid as Nunya's and Whizkid's with electrical issues.

He's basically been walking me through every details regarding my basement renovation project.

reply to Goober

reply to pike
When I'm in a typical basement where spray foam hasn't been used, there's an odd coolness that I feel. Even when the basement is heated, I still get a "basement feel". It's like the concrete is sucking moisture out of me or something and I can always smell that basement smell. It's hard to describe, but I hate basements and the feel I get.

Because of the above, I never wanted to finish the one in our own home. But about five years ago I let my wife talk me into getting our basement done. We talked to four different companies and actually walked around in people's basements to see the quality of work and to get an idea of design etc. Of those four company's basements, only a single one did spray-foam insulation. And I have to say, even my wife who thinks I'm weird about basements, agreed that the spray foam insulated basements felt different--like they weren't a basement. For a couple of years afterwards even my kids used to comment about basement smells in other people's houses and how they didn't like going into the basement of others.

Our basement is great and I have no problems going down there. It feels different than most and has no smell. We not only spray foam insulated the living space area but the entire basement including crawl space as well. That may have made a difference as well.

At any rate, it makes sense to us since we live there and can actually feel the difference when we compare our basement to others.
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Biden--the bastard child of Otis the Drunk and a laughing hyena. No wonder the US is hurting. Vote Romney/Ryan 2012 and restore sanity.

The initial visits were all upper end basement remodels done by well known building companies. One of the companies was the one who did a large remodel for us and who we really liked. But their basements again just didn't feel right to us. And the only difference we could come up with was the kind of insulation being used. The basements of homes that we go to nowadays, who knows. I wouldn't doubt that some are done by hacks.

But after our visits, we decided that spray foam was the way to go. So in the new non-basement remodeling that we're going to be doing soon, it's all going to be spray foam where insulation is needed. We're believers.
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Biden--the bastard child of Otis the Drunk and a laughing hyena. No wonder the US is hurting. Vote Romney/Ryan 2012 and restore sanity.

Yeah, the price is high for sure.

I think at the end of the day spray foam isn't necessary and other methods, when done well, take you probably 90%+ of the way there.
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Biden--the bastard child of Otis the Drunk and a laughing hyena. No wonder the US is hurting. Vote Romney/Ryan 2012 and restore sanity.

reply to QuaffAPint
Check around you may find that having a pro spray foam your walls may not be that far over do it yourself, my son-in-law had the attic of an addition done- he said it cost him about $400 more than fiberglass but was done in 2 hrs. It would have taken more than a day to staple up batts and then you have to deal with fiberglass every time you go into attic, he has also said he's really glad he did it.
He had 8in sprayed to plywood and rafters not attic side of drywall.

This is the problem with percentages though (and we're probably drifting this thread,) however, we pay with dollars, not percentages. You don't deposit percentages in the bank, you deposit dollars. I want to know how many more *dollars* it is costing. That's my point.

The size of the compared projects *both* need to be large in order for percentages to have merit. When one is small and the other large, it becomes skewed before you even start to compare.

On the other hand, percentages help in making a relative value judgement. Spray foam that costs $2K on a $60K basement project is of much more value to me than spending $1K on foam for a $4K shed. The actual dollar amounts in that case don't matter much to me, but the percentage in terms of overall cost do.
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Binders and Big Bird, because there's nothing else to worry about. Drop the stooges and vote Romney/Ryan in 2012.

Percentages are for losers

In a down market your mutual fund may lose 20% vs. another fund that's down 30%. Are you a winnner?

No. You've still lost 20% of your equity

That has to be one of the worst analogies I've ever heard.