Spray foam diy

[Seasoned Oak]

Great stuff is best for small gaps. For larger areas i use sheet foam and keep about a quarter in.gap all around to be filled with great stuff in a can. The canned great stuff is also a great adhesive. When using on windows and doors the foam will actually glue the product into the opening. The sheet foam seems a lot cheaper than having an area spray foamed.IMO

 

[mass_burner]

Yea, I took a closer look and its not bad as I thought. Pretty smooth on the ceiling.

Should I use 2" xps? Anything between board and ceiling?

 

[mass_burner]

Yea, I took a closer look and its not bad as I thought. Pretty smooth on the ceiling.

Should I use 2" xps? Anything between board and ceiling?

Anyone?

 

[maple1]

Not sure what you are asking there. Are you asking about putting 2" on the ceiling? Or putting 2" in the spaces you were talking about before, edges up against the ceiling? If the former, I'm not thinking anything else is needed in between. If the latter, spray can foam to seal edges as already mentioned.

(I'm no insulation pro....)

 

[mass_burner]

Not sure what you are asking there. Are you asking about putting 2" on the ceiling? Or putting 2" in the spaces you were talking about before, edges up against the ceiling? If the former, I'm not thinking anything else is needed in between. If the latter, spray can foam to seal edges as already mentioned.

(I'm no insulation pro....)

Yes, I was asking if 2" xps specifically is the material I should use, and if I should put anything between the xps and the joist bay surface.

Also, this space I'm treating abuts the garage, which is insulated with blown in cellulose. Where the two rooms meet, at the ceiling, there is just a folded piece of insulation to keep the cellulose back.

How should I handle this border area?

 

[mass_burner]

Wait...I was at HD today and 2" xps is r10, at $20/2'x8'. But attic batt pink insulation is r30 at less per sq.ft.

Why am I doing foam board again?

 

[maple1]

You can go pink if you want, it's your $$.

 

[mass_burner]

You can go pink if you want, it's your $$.

You mean my $$ to save?

 

[maple1]

Save or spend, whichever way you want to say it.

Fiberglass won't do much for stopping air infiltration, mice really like it, it can soak up water, and can get you itchy when handled - but it is cheaper. I did my rim joist area in my basement with fiberglass some 20 years ago, it was a very tedious & not very pleasant job. Cut to the right size, stuff it in, than I stapled/caulked vapour barrier over it. I don't think I'd go through that again - although I think it has done the job. Pretty sure if I was doing it again, I would cut sheets of foam board to loose fit & seal it in place with spray foam around the edges.

 

[moey]

Wait...I was at HD today and 2" xps is r10, at $20/2'x8'. But attic batt pink insulation is r30 at less per sq.ft.

Why am I doing foam board again?

Fiberglass insulation will fall down/settle when used in a ceiling joist. So you have an air gap between the surface to be insulated and the fiberglass basically making it useless or nearly useless.

Foamboard is $33.92 at lowes Id suggest looking on ebay or the post office for a 10% coupon and look for a discounted giftcard they regularly have them on sale on ebay $100 gift card for $90. So your $33 sheet is then ~$26.

 

[Seasoned Oak]

Almost everything around here is cheaper at Home Depot than it is at lowes. Im looking at a .08 gal flush niagra toilet that gets great reviews,and its $149 at HD and the very same one is $256 at Lowes. MORE THAN $100 more Quite the difference and i need 3 of them So i always always check HD as well as lowes for everything i buy.

 

[mass_burner]

Okay, now I'm back where I started. This area is cold and makes part if the kitchen floor cold above it, so I need max r value. Its also s heavily traveled area, as it's the only access to the garage/ basement from the house above. When removing the old insulation, I didn't see any signs of pests.

Other issues aside, will I get a higher r value with 9" r 30 pink insulation?

 

[moey]

Packing fiberglass more densely does not increase its R value. However the last thing you want using fiberglass in the area your describing is not having it pushed tight up against the surface your insulating.

Id strongly suggest you go the foamboard route or spray foam. The R value of fiberglass is essentially what was measured in a lab with it sandwiched and sealed between two surfaces all of which you dont have. R-10 foam properly installed will perform better then R-30 dropping from your ceiling.

 

[semipro]

Other issues aside, will I get a higher r value with 9" r 30 pink insulation?

Probably not in actual application.
Firstly, its challenging to do a great job of installing FG batts. Their structure doesn't work well for getting a good fit without cavities and poor surface contact.
You'd still need to air seal below the insulation to prevent convective air currents from defeating your efforts.
Also, as moey mentions its hard to get batt insulation to stay in intimate contact with a horizontal surface above, which also leads to losses from air currents.
Consider also that your floor joists may create losses through thermal bridging. The R-value of the wooden joist over its height may well be less than the insulation you're installing. You can attach a layer of rigid foam across the bottom of the joists to address this. Softwoods like southern yellow pine have an R value of about 1 per inch.

 

[mass_burner]

The joist bays are 15". The 2' xps is 24". Can I use 12" strips and fill 1.5" on each side? Is that too large a gap?

 

[maple1]

How high are the bays?

 

[semipro]

The joist bays are 15". The 2' xps is 24". Can I use 12" strips and fill 1.5" on each side? Is that too large a gap?

Probably. The panel foam is cheaper by volume than the can so it may not make sense.

 

[peakbagger]

HD in my area stocks the two component kits. http://www.homedepot.com/p/Touch-n-...Component-Spray-Foam-Kit-4006022200/204962748. It saves shipping costs which can be steep for kits.

I used a two component kit several years ago to do a flash and batt on a wall I opened up. A lot nicer looking than anything I could do with "great stuff" type foam,.

It is depressing to see how much trash a two part kit generates.

 

[moey]

The joist bays are 15". The 2' xps is 24". Can I use 12" strips and fill 1.5" on each side? Is that too large a gap?

Over the whole length thats to much. You want about 1/4 to 1/2 gap on both sides. If you bought a 4 * 8 sheet you would have about 6 inches waste on one side after you cut your pieces out. You can probably find a place to use it somewhere I would suspect.

 

[maple1]

Actually he'd only have 3" waste with a 4x8 sheet. But that depends also on the height.

 

[mass_burner]

Joists are 9 5/16 tall. The space between bays are 14 to 14 7/8, their not all the same.

 

[maple1]

You can get 16 pieces of 9.5x14.5, out of a 2x8 sheet. You'll have 4 pieces of 5x5 left over.

 

[begreen]

The joist bays are 15". The 2' xps is 24". Can I use 12" strips and fill 1.5" on each side? Is that too large a gap?

Can you get it in 48" sheets instead? That way you get 3 - 15" cuts. 3" strip left over.

 

[mass_burner]

Can you get it in 48" sheets instead? That way you get 3 - 15" cuts. 3" strip left over.

Probably, I have seen them by before. Should I cut a pieces of foam to seal in the cellulose blow in the adjacent garage?

 

[maple1]

Can you get it in 48" sheets instead? That way you get 3 - 15" cuts. 3" strip left over.

He'd get 2 more pieces out of out of 2 - 2x8 sheets, than by doing that.

32 vs. 30.