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Camelot One
Premium,MVM
join:2001-11-21
Greenwood, IN
kudos:1

Basement insulation question

I am about to start framing my basement. For now just the theater room, with a bedroom and bathroom to come later. The exterior is wrapped, with proper drainage. No water penetration issues.

But I am running into conflicting theories on the interior insulation.Both sides are dealing with warm/moist air in the basement condensing on the cold basement walls. Deck footings are required to be 36" here, the state water line freeze depth is 54". So I guess that is the temperature depth I need to address.

One side says to attach 1-1/2" - 2" rigid foam board straight to the concrete, forming a thermal and vapor barrier, then frame the walls right against it. The idea being that with the foam board creating a thermal barrier, warm air wouldn't touch the cold concrete, and thus no condensation would form. This option would add about $500 to the first room I am working on, and another $750 for the rest of the basement later.

The other theory says foam board is a waste of money, and to just frame the walls out an inch or so, leaving an air gap between the framing and concrete. The idea being that the air flow would dry out any condensation that does form on the concrete.

Both theories have non-paper backed insulation between the joists. The county inspector says either option is allowed, but offered no recommendation on which to use.

Anyone have thoughts? And would steel vs wood framing make any difference on those options? I want to do it right, but I don't want to just waste money.



tschmidt
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join:2000-11-12
Milford, NH
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When I finished our basement 30ish years ago nailed strapping directly to the wall, used 2" foam board and sheet-rocked over the foam, screwed into the strapping.

The problem with that approach is untreated wood is in direct contact with cold concrete. No vapor barrier is perfect, moisture still wicks through from the outside and moisture will condense from the inside.

If I was doing it again I'd attached foam board directly to the wall, then strap it, then Sheetrock over the strapping. This keeps the wood dry and provide a nice chase for wiring and plumbing and doesn't waste as much space as building a stud wall around the perimeter. This of course assumes you have reasonable smother and straight walls.

/tom.


H_T_R_N
Premium
join:2011-12-06
Valencia, PA
kudos:1
reply to Camelot One

Frame the walls 2 inches off the block and have spray foam done by a pro. You will LOVE it.


rody_44
Premium
join:2004-02-20
Quakertown, PA

I framed about two inches out and used regular insulation. That two inches comes in handy if you ever want to fish lines behind it later.



UHF
All static, all day, Forever
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join:2002-05-24
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reply to Camelot One

said by Camelot One:

One side says to attach 1-1/2" - 2" rigid foam board straight to the concrete, forming a thermal and vapor barrier, then frame the walls right against it.

That's how I did it, and how several contractors advised me to do it.


Msradell
P.E.
Premium
join:2008-12-25
Louisville, KY

said by UHF:

said by Camelot One:

One side says to attach 1-1/2" - 2" rigid foam board straight to the concrete, forming a thermal and vapor barrier, then frame the walls right against it.

That's how I did it, and how several contractors advised me to do it.

I did the same thing it seems to be working very well. Takes a little more space and some of the other options but seems to provide the best solution.
--
Written using Dragon NaturallySpeaking


Camelot One
Premium,MVM
join:2001-11-21
Greenwood, IN
kudos:1

Is the foam board your only vapor barrier, or did you put plastic between the studs and drywall?



bryank

join:2000-03-23
Plainfield, IL
reply to Msradell

said by Msradell:

said by UHF:

said by Camelot One:

One side says to attach 1-1/2" - 2" rigid foam board straight to the concrete, forming a thermal and vapor barrier, then frame the walls right against it.

That's how I did it, and how several contractors advised me to do it.

I did the same thing it seems to be working very well. Takes a little more space and some of the other options but seems to provide the best solution.

So what if the OP needs to mount something that needs structure? (ie. flat panel TV, shelving, etc?) Strapping is not structurally sound, but I guess it all depends on what is used and how it's secured.


Camelot One
Premium,MVM
join:2001-11-21
Greenwood, IN
kudos:1

In this case the only thing mounted to the walls will be some fabric covered frames for sound purposes. I will have to install receptacles to meet code, but I guess you just cut out enough insulation for the boxes.



nunya
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O Fallon, MO
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reply to Camelot One

Steel vs. wood, I would do a price comparison. Personally I prefer steel and can work faster with it. Cost-wise, sometimes wood makes sense. Both are commodities and the price fluctuates.
Right now, I think wood is a few cents less per 2 x 4. The thing I like about steel is it doesn't warp or get termites.
--
If someone refers to herself / himself as a "guru", they probably aren't.



rfhar
The World Sport, Played In Every Country
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join:2001-03-26
Buicktown,Mi
Reviews:
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reply to Camelot One

I insulated my basement walls leaving one inch between the cement and the stud as advised by the contractor who built my house and have had no moisture problems. I believe either method would likely end up pleasing you in the long run. I do though have a problem. In the winter my basement is nice and warm. I even covered the return vent on my warm air furnace. But in the summer the uninsulated floor keeps the area quite cool. I did not do anything to the floor other than cover it with a rug as I have a seven foot high wall down there since I live by a small lake or pond.
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ArgMeMatey

join:2001-08-09
Milwaukee, WI
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reply to H_T_R_N

said by H_T_R_N:

Frame the walls 2 inches off the block and have spray foam done by a pro.

Take a look at how they did it in the current This Old House. I think it's after the hail simulation in this video:
»www.thisoldhouse.com/toh/tv/vide···,00.html


Msradell
P.E.
Premium
join:2008-12-25
Louisville, KY
reply to bryank

said by bryank:

So what if the OP needs to mount something that needs structure? (ie. flat panel TV, shelving, etc?) Strapping is not structurally sound, but I guess it all depends on what is used and how it's secured.

If you read what was written you will see that it says frame the walls straight against it. Framing consists of using 2x4 or metal studs to form a wall. Either of the other sufficiently strong to hold anything that is currently hung on a wall. No mention was made of using furring strips or anything of later gauge material.
--
Written using Dragon NaturallySpeaking

H_T_R_N
Premium
join:2011-12-06
Valencia, PA
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reply to ArgMeMatey

said by ArgMeMatey:

Take a look at how they did it in the current This Old House. I think it's after the hail simulation in this video:
»www.thisoldhouse.com/toh/tv/vide···,00.html

Video does not play.


Cho Baka
Premium,MVM
join:2000-11-23
there
kudos:2

Played ok for me.

Maybe try reloading the page?
--


themagicone

join:2003-08-13
Osseo, MN
reply to Camelot One

I'd second having it spray foamed. Will create nice sound dampening for a theater.



ArgMeMatey

join:2001-08-09
Milwaukee, WI
kudos:2
Reviews:
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reply to H_T_R_N

said by H_T_R_N:

Video does not play.

I may have had an issue with ABP or pop-up blocker when I first used the site for video months ago. Can't recall exactly and it works OK now.

To summarize, the house has a rubble stone foundation. A mason mortared the stones with "special" waterproof mortar and then, directly on the stone, they sprayed (If I recall correctly, haven't watched since last week) closed cell foam with a new water-based propellant, lower odor than the old stuff. Stud wall is not attached to the rubble stone, from what I could see.
--
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pende_tim
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join:2004-01-04
Andover, NJ
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reply to H_T_R_N

said by H_T_R_N:

Video does not play.

I had to pause AdBlock so it could load some stuff before the video would play.
--
The difference between genius and stupidity is that genius has its limits.


Camelot One
Premium,MVM
join:2001-11-21
Greenwood, IN
kudos:1
reply to Camelot One

I looked into the spray foam option. It is just too expensive to fit in the budget.
I found several government references listing R11 (total) being the sweet spot for basement insulation in my area. I decided to go with 1" XPS (R5) glued to the concrete, with a framed 2x4 wall up against it, and more insulation between the joists. I picked up some 2" to go around the rim joist, which I will seal with canned spray foam.

I'll be using Mineral Wool (R15) for the interior walls, not sure if I should use it on the exterior walls or not. I know it's better for sound, but I haven't found much info far as mold/mildew resistance. I want to use it for the ceiling, but I haven't found a local supplier with 24" widths. Cutting/cramming 16" between 24" joists doesn't sound like much fun.

So far things haven't gone very well. I started yesterday removing the builder installed fiberglass batts from the top of the walls, which required buying an angle grinder to cut out the nails. Managed to catch a piece of slag on my arm, which melted a piece of my shirt to my arm. Following that I bought the XPS at Menards, loaded the first piece in the truck, then had to chase the others across the parking lot after a sudden gust of wind. Sat down to watch some TV last night, and the Onkyo receiver, which I had planned to move to the theater room, decided to die. 26 days past warranty.

Hopefully the rest of this project goes better.



pende_tim
Premium
join:2004-01-04
Andover, NJ
kudos:1
Reviews:
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I believe mineral wool is what you want to use in potentially damp places, like basements. By the nature of the product there are no organics in it that can promote growth of mold causing bacteria.

Also it is very easy to work with: It cuts easily and is not itchy at all.

If you use it on the 24" joists simply cut a bunch of pieces 22 1/2" long and put them in sideways. If you do not want to use a knife to cut the mineral wool, it also tears/breaks easily.

What are you using to glue the XPS to the basement wall with? I am going to be attaching a bit to a wall below grade for a corner where I have condensation in the summer.

BTW don't forget to seal the vertical joints in the XPS where it meets the piece next to it as well as where the XPS meets the floor. The canned foam will work nicely for that. The key here is to prevent as much moisture as possible from migrating through the walls.
--
The difference between genius and stupidity is that genius has its limits.



Camelot One
Premium,MVM
join:2001-11-21
Greenwood, IN
kudos:1

1 recommendation

said by pende_tim:

What are you using to glue the XPS to the basement wall with?

"Loctite PL 300 Foamboard Construction Adhesive" is what I grabbed yesterday. Looks like it is designed for just this use. I also have "IPG Red Sheathing Tape" for the seams, which says "for use on poly plastic". The guy at Menards said that was the right stuff, but I'll double check that before I put it up. I expected to find something by Corning, but they didn't have anything.

H_T_R_N
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Valencia, PA
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reply to ArgMeMatey

said by ArgMeMatey:

Take a look at how they did it in the current This Old House. I think it's after the hail simulation in this video:

Yep, thats the way!


bryank

join:2000-03-23
Plainfield, IL

1 edit
reply to Msradell

said by Msradell:

If you read what was written you will see that it says frame the walls straight against it. Framing consists of using 2x4 or metal studs to form a wall. Either of the other sufficiently strong to hold anything that is currently hung on a wall. No mention was made of using furring strips or anything of later gauge material.

Ok I must of misread, or my mind was wandering. Because I have seen in many basements this happening. Foam board glued to the concrete, 1x's (furring strips)then tapcon'd through the foam board, then sheet rock over.