Small basement insulation project

[mustash29]

The house is a tri-level with a very small actual basement. My basement walls are 8" poured concrete. The north and east walls are 7.5' high and are the only two exterior walls that see outside weather. The south & west walls are 3.5' high and form the foundation for the garage and rec room slabs respectively.

Shopping for stuff to box in my wood boiler storage tanks, I found a very good deal on polyisocyanurate sheets, so I picked up enough to insulate the two exterior basement walls too. The polyiso sheets have a "moisture barrier" on both sides that resembles a thin layer of felt. If you pick at it a little bit it will peel right off.

What is the best way to attach the sheets to the poured concrete walls? Blobs of adhesive like liquid nails / construction adhesive? I'm hoping to avoid drilling, nailing or screwing into the poured concrete.

Should I leave the moisture barrier coating on both sides, or remove the layer that will be against the concrete?

The basement is dry, 18 years and never had any water down there. Summer humidity levels have never really been a problem either. When it gets hot & humid in the summer the upstairs A/C dehumidifies the whole house very well. The basement is also going to contain a Nyletherm HPWH.

 

[mustash29]

This is not the exact add, but the pic looks like the same stuff I have.

(broken link removed to http://newhaven.craigslist.org/mat/4748282959.html)

 

[velvetfoot]

The foam might not like your normal construction adhesive; probably would need polyurethane adhesive. I'm thinking bare xps here-not sure about your stuff.
You have to hold in place for a while which isn't that easy. Also, chances are you should cover it with 1/2" of sheetrock for fire reasons; glue won't make it for that.
I don't know what the felt is for. I have some polyiso stuff with foil on both sides.

 

[moey]

The problem with not screwing it how do you plan to hold it to the wall until the adhesive drys? Your wall more then likely is not flat neither is your foam so you need to apply some type of force to seal it up against the walls. I used xps rigid foam with a bead of great stuff and 1 * 3's screwed into the wall. It sucks drilling holes I know.

I would not want the felt on the insulation.

Your basement is not dry concrete holds moisture it just evaporates before you see it running down the sides of your wall.

 

[velvetfoot]

Hey moey, how did you use the Great Stuff, if I may ask. I used polyurethane adhesive for my basement job, and it wasn't that great. I hate those Great Stuff cans but I've since bought an applicator gun, which is great! Just wondering if I could've done it better/easier, lol.

 

[semipro]

There seems to be some good info here on the subject.
http://www.greenbuildingtalk.com/Forums/tabid/53/aff/14/aft/77536/afv/topic/Default.aspx
http://www.greenbuildingadvisor.com...fiber-faced-polyisocyanurate-ok-exterior-insu

That's a fiber facing on the boards you bought. I believe it contains fiberglass so if you're sensitive to that beware.

Unlike XPS, Polyiso will absorb water. I'm not sure it should be used for basement walls. Perhaps the links above will provide more info. I did not read them through.

 

[semipro]

Also, chances are you should cover it with 1/2" of sheetrock for fire reasons; glue won't make it for that.

Actually I and others here have used glue successfully to adhere gypsum boards to XPS foam using the proper Loctite foam board adhesive.
Not sure about how it would work with polyiso though.

 

[velvetfoot]

Actually I and others here have used glue successfully to adhere gypsum boards to XPS foam using the proper Loctite foam board adhesive.
Not sure about how it would work with polyiso though.

But even if the sheetrock didn't fall off the wall over time, if one was concerned about fire protection, would that be okay?

 

[semipro]

But even if the sheetrock didn't fall off the wall over time, if one was concerned about fire protection, would that be okay?

Good question.
The code calls for the sheetrock or other fire resistant materials but doesn't specify how they are attached. In another recent thread someone reported having to break the sheetrock off in pieces after it had been glued on.

 

[moey]

Hey moey, how did you use the Great Stuff, if I may ask. I used polyurethane adhesive for my basement job, and it wasn't that great. I hate those Great Stuff cans but I've since bought an applicator gun, which is great! Just wondering if I could've done it better/easier, lol.

Well great stuff was not that great either. It does work though. I put three vertical 1*3 fur stripping on a 4 * 8 sheet of xps and then put a small bead of great stuff on the back of the sheet where the furring strip would apply pressure. I predrilled all the holes and would hang two 4 * 8 sheets with one can of great stuff. You have to be careful not apply to much as it expands and can push the sheet out away from the wall, ask me how I know. Also used the great stuff to seal along the floor and the sheet and between sheets. It does give a good seal to the wall.

Then put the drywall over the furring strips and had enough room for shallow electrical outlet boxes.

 

[DickRussell]

GBA has a good blog in this subject: http://www.greenbuildingadvisor.com/blogs/dept/musings/how-insulate-basement-wall
It references a good piece from Building Science Corp. (http://www.greenbuildingadvisor.com...usses-basement-insulation-and-vapor-retarders), which covers the matter of basement walls drying to the interior under the subheading "News story #2: Basement walls don't need to dry to the interior."

 

[velvetfoot]

I put on two layers of xps, with the first layer held on by furring and the second layer I milled grooves so they would go over the furring strips. Milled out grooves for electric wire and boxes. Screwed drywall onto furring strips which held everything together well. For caulking I used the ordinary stuff.

 

[begreen]

I put up foam sheets to insulate our crawlspace 8 yrs ago with a good poly adhesive. They are still rock solid and going nowhere. Buy it by the case in the big tubes for a better price break and get a jumbo gun. You will use a lot of adhesive per 4x8' sheet.

http://www.homedepot.com/p/Loctite-...0474?N=5yc1vZc5dkZ1z0t8pk#product_description

 

[Circus]

If it was me, I'd consider insulating the exterior then covering it with dirt and that grey pebble looking vinyl. Just a thought. First check if polyiso gets crushed easily.

 

[moey]

I put on two layers of xps, with the first layer held on by furring and the second layer I milled grooves so they would go over the furring strips. Milled out grooves for electric wire and boxes. Screwed drywall onto furring strips which held everything together well. For caulking I used the ordinary stuff.

Holy cow You went all out. Way to go.. I could not bring myself to put up two layers but my BTU's are relatively inexpensive with my geo heat.

 

[BIGDADDY]

Here is another way

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[begreen]

Those plastic anchors are slick.

 

[BIGDADDY]

Those plastic anchors are slick.

$135 for 250. 4" long.

 

[begreen]

I think I would go with just the PL2 foam board adhesive then. Try to buy it by the case for a better price. It should be significantly below $135.

 

[BIGDADDY]

Yes that what I am doing, but if it doesn't stick I can always get the anchors

 

[moey]

I put on two layers of xps, with the first layer held on by furring and the second layer I milled grooves so they would go over the furring strips. Milled out grooves for electric wire and boxes. Screwed drywall onto furring strips which held everything together well. For caulking I used the ordinary stuff.

How do you mill out grooves that stuff isn't exactly safe to have blowing around like dust when you cut a groove?

 

[velvetfoot]

It wasn't that dusty, really. A mess, yes. It mostly landed on the floor. Easily blown by a breeze, but not bad. Took a lot of time though.

 

[moey]

It wasn't that dusty, really. A mess, yes. It mostly landed on the floor. Easily blown by a breeze, but not bad. Took a lot of time though.

What did you mill them out with? One side of my basement is a walkout and mostly exposed Ive contemplated putting two layers of foam on it.

 

[velvetfoot]

I used a dado blade on a table saw.
What's interesting about the completed wall is that you can bounce off it and nothing breaks.