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QuaffAPint
A Big Thanks To The Troops

join:2001-01-10
Downingtown, PA
Reviews:
·Verizon FiOS

1 recommendation

Insulating Behind Studs

Click for full size
basement wall
Live in PA and working on finishing our basement. We have one exterior wall that was studded. Now, I'm trying to find the best/cheapest/easiest/best bang for the buck way to insulate behind the studs. It's just one wall about 21'x8'.

In hindsight I would have done foam board prior to studding. Now, our plan was to just go through the pain of cutting the board in smaller pieces and lifting it over the cables behind the studs, slide them all together and tape em.

But, we also have that annoying pipe, so we would have to measure around that. And do we need to Great Stuff all around that pipe right against the exterior wall?

There's also the spray foam option, I guess, but I don't know how much that would cost, and we still have that pipe to contend with.

Looking for suggestions and thanks for sharing any!
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AsherN
Premium
join:2010-08-23
Thornhill, ON

Fiberglass?



ropeguru
Premium
join:2001-01-25
Mechanicsville, VA

1 recommendation

reply to QuaffAPint

Roxul insulation

»www.roxul.com/home



rfhar
The World Sport, Played In Every Country
Premium
join:2001-03-26
Buicktown,Mi
reply to QuaffAPint

I used fiberglass but my studs are one inch away from the cement walls.



QuaffAPint
A Big Thanks To The Troops

join:2001-01-10
Downingtown, PA
Reviews:
·Verizon FiOS
reply to QuaffAPint

I've got like 2.5 - 3.5 in of clearance from wall to stud. I was thinking roxul as well, but they still say you need something against the cement first (some roxul board).

I guess the question is what goes against the cement wall in this scenario. Since I can't just place roxul or fiberglass right against it.
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ropeguru
Premium
join:2001-01-25
Mechanicsville, VA

What about just going with a spray on insulation. That will adhere to the wall, close up the gap and provide insulation.

Edit to add:

Read here »DIY Spray Foam Kit Review


Badonkadonk
Premium
join:2000-12-17
Naperville, IL
kudos:5

Best suggestion. The air also feels better on the skin in the basement when it's spray foamed.



alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1
reply to ropeguru

Guys, he already has a gap between the studs and concrete walls.

OP, I don't see a gasket seal under your sole plate. Is it pressure treated wood for the sole plate?

said by ropeguru:

Roxul insulation

»www.roxul.com/home

Seconded.
It has a higher R value per inch of thickness than fiberglass
If it gets wet, it won't lose its textile strenght, meaning it just needs to dry and it's good to go.
It cannot burn.

If he has a 2" gap between the concrete wall and the studs, he can even use roxul batts for 2x6 studs (R22 value).

But I don't know what you'd use to seal the gap behind the studs. The roxul would be in the cavity and can touch the wall, but it won't expand behind the studs.

Maybe he can fill one cavity with roxul, then spray foam behind the two studs from the adjacent cavities, then fill the adjacent cavities with roxul and repeat. That way the spray foam would only expand behind the studs and be molded into place by the roxul batts.

said by QuaffAPint:

But, we also have that annoying pipe, so we would have to measure around that. And do we need to Great Stuff all around that pipe right against the exterior wall?

I have had to deal with a central vac pipe as well. What I did is cut out a section of the roxul batts to accomodate the pipe.
It has less R value around the pipe, but there's not much more you can do other than waste cans after cans of great stuff to encase it.


cowboyro
Premium
join:2000-10-11
Shelton, CT
Reviews:
·AT&T U-Verse

said by alkizmo:

said by ropeguru:

Roxul insulation
»www.roxul.com/home

Seconded.
It has a higher R value per inch of thickness than fiberglass

Same R-value. R15 for 3.5".
»www.roxul.com/residential/produc···E2%84%A2
»www.homedepot.com/Building-Mater···ications


alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1

said by cowboyro:

Same R-value. R15 for 3.5".

My bad
When I started plans on my basement renovation, there was only this stuff in store
»www.homedepot.ca/product/r-12-sp···i/925593

I guess it's a matter of whichever is cheapest for the same R value.


nunya
Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:12
Reviews:
·Charter
·voip.ms
·surpasshosting
reply to QuaffAPint

I know there's going to be hurt feelings, but it needs to be said:
I would fix the wiring before considering any insulation (bundling, improperly supported, improperly secured). Why are the outlets in before the drywall?
--
If someone refers to herself / himself as a "guru", they probably aren't.



QuaffAPint
A Big Thanks To The Troops

join:2001-01-10
Downingtown, PA
Reviews:
·Verizon FiOS

said by nunya:

I know there's going to be hurt feelings, but it needs to be said:
I would fix the wiring before considering any insulation (bundling, improperly supported, improperly secured). Why are the outlets in before the drywall?

If you mean the wiring on the top. It is original to the house and has passed code. There is a couple network cables zip tied by the verizon guy, which is what looks loose.

As far as the outlets, I want them wired up to test all the electrical prior to having the drywall in place - now they should be unscrewed, that I agree with.
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cowboyro
Premium
join:2000-10-11
Shelton, CT
Reviews:
·AT&T U-Verse
reply to QuaffAPint

Cut 1.5" wide strips of 3.5" fiberglass and put behind studs. Fill the cavities with 5.5" fiberglass. Assuming your wall is a 6".
I'm not sure about the cost/benefit of only insulating 1 wall with spray foam. The cost per sqft would probably be high given just one small wall, but it doesn't hurt getting a quote.
In 4 months of 40F average temperature difference between in-out, the savings are only about $15 if you burn oil for heating. Kinda "meh".



QuaffAPint
A Big Thanks To The Troops

join:2001-01-10
Downingtown, PA
Reviews:
·Verizon FiOS

said by cowboyro:

Cut 1.5" wide strips of 3.5" fiberglass and put behind studs. Fill the cavities with 5.5" fiberglass. Assuming your wall is a 6".

Can you put fiberglass right up against an exterior cement wall?
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cowboyro
Premium
join:2000-10-11
Shelton, CT
Reviews:
·AT&T U-Verse

said by QuaffAPint:

said by cowboyro:

Cut 1.5" wide strips of 3.5" fiberglass and put behind studs. Fill the cavities with 5.5" fiberglass. Assuming your wall is a 6".

Can you put fiberglass right up against an exterior cement wall?

I'd put a vapor barrier anyway...


alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1

1 edit
reply to QuaffAPint

said by QuaffAPint:

Can you put fiberglass right up against an exterior cement wall?

I would venture to say no

What I "would" do it cut up a foam board to fit in a stud cavity.
Place that cut board in "left" cavity, come in from the "right" cavity with Great Stuff to foam up the space behind the "left" stud, then place another cut up foam board in the "right" cavity, and continue moving that way.

Don't you regret simply not putting foam boards at the start?


QuaffAPint
A Big Thanks To The Troops

join:2001-01-10
Downingtown, PA
Reviews:
·Verizon FiOS

said by alkizmo:

said by QuaffAPint:

Can you put fiberglass right up against an exterior cement wall?

I would venture to say no

That's what I thought too - which is why I thought I would have to do the foam board first.
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Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1
Reviews:
·Millenicom
reply to cowboyro

said by cowboyro:

said by QuaffAPint:

said by cowboyro:

Cut 1.5" wide strips of 3.5" fiberglass and put behind studs. Fill the cavities with 5.5" fiberglass. Assuming your wall is a 6".

Can you put fiberglass right up against an exterior cement wall?

I'd put a vapor barrier anyway...

Out of curiosity I searched the web and here is what I found at an EPA site. Google is an excellent source for reference

»www.epa.gov/indoorairplus/techni···_12.html

“An appropriate assembly for the inside of a basement wall consists of 1 in. of plastic foam board or closed-cell polyurethane spray foam followed by a stud wall with fiberglass insulation filling the cavities. This assembly is covered with moisture- and mold-resistant gypsum board covered by two coats of latex paint. The foam board serves two purposes: providing a capillary break between the foundation wall and the stud wall and keeping warm, humid basement air away from the earth-chilled foundation. It is good practice to put 1 in. of foam board beneath the sole plate of the stud wall and the basement floor and to leave a ½-in. gap between the basement floor and the bottom of the gypsum board. Doing so provides protection from minor floods and damp concrete floors.”


alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1

makes sense.
That's what I was recommended to do for my basement. I put 1" rigid foam against the concrete, tuck taped between boards, spray foamed large gaps (like behind ducting). I find 1" under the sole plate to be a bit extreme, especially if you have double sole plate, that would require something like 5" tapcons (if those even exist). I used a sill gasket roll, which is made for protecting the sole plate from the concrete slab.

It isn't too late for OP to do damage control with my tedious suggestion (cutting boards, spray foaming etc).

edit - Maybe he can remove a few studs in order to fit in full size boards and slide them behind the rest of the frame.


Tig

join:2006-06-29
Carrying Place, ON
Reviews:
·voip.ms
·TekSavvy DSL

1 edit
reply to QuaffAPint

Here, building code requires some sort of vapor barrier on on the portion of the wall below grade to protest the insulation, Even though the outside of the foundation is also sealed below grade (tar)
Bitumous paper is used inside. (tar paper).
I used R14 roxul on my sub grade walls.



KrK
Heavy Artillery For The Little Guy
Premium
join:2000-01-17
Tulsa, OK
reply to ropeguru

Nice, that stuff is impressive.

Fireproof, water repellent, Energy efficient, and sound proofing.

Nice.


MaynardKrebs
Heave Steve, for the good of the country
Premium
join:2009-06-17
kudos:4

2 edits

1 recommendation

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.



Jack_in_VA
Premium
join:2007-11-26
North, VA
kudos:1

»Re: Insulating Behind Studs


MaynardKrebs
Heave Steve, for the good of the country
Premium
join:2009-06-17
kudos:4

Not all foam is created equal as far as vapour permenace is concerned.
EPS - expanded foam (the white grainy stuff) - is vapour permeable.
Extruded foam (like the blue Dow Styrofoam SM) is not vapour permeable.
Spray polyurethane foam is not vapour permeable if applied thick enough (ie. 1"-2" of 2lb. foam) or thinner if higher density foam. The "pound" rating is the weight of 1 cubic foot of properly expanded and cured spray foam.


alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1
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.



pike
Premium,MVM
join:2001-02-01
Washington, DC
kudos:3
reply to Badonkadonk

said by Badonkadonk:

Best suggestion. The air also feels better on the skin in the basement when it's spray foamed.

Can you elaborate? This statement makes absolutely no sense to me.


alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1

said by pike:

Can you elaborate? This statement makes absolutely no sense to me.

Of course it makes sense!
The basement air feels better to spray foamed skin.
It makes a killer winter suit as well.

Badonkadonk
Premium
join:2000-12-17
Naperville, IL
kudos:5
Reviews:
·Dish Network
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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alkizmo

join:2007-06-25
Pierrefonds, QC
kudos:1

said by Badonkadonk:

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.

You sure you didn't just visit basements that had POOR insulation and compared them to spray foamed insulated basements?

On a very productive day, I went from no insulation in my wall frames to full coverage of roxul batts (R22) and half my joist cavities sealed with R22 roxul + 2" XPS.

I could VERY much feel the difference. The humidity rose (I had a meter), the air was more "warm". The shock was more obvious after I went back to the basement after taking an hour break. Since my body temperature dropped from relaxing, I expected to walk back in there feeling a bit chilled (As it was always before). It was actually comfy.

As for the smell, well, I blame poor vapor barriers, carpets, and age of the renovation (You probably visited freshly renovated basements insulated with spray foam).

Badonkadonk
Premium
join:2000-12-17
Naperville, IL
kudos:5
Reviews:
·Dish Network

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.
--
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.