# Spray foam diy



## mass_burner (Mar 22, 2016)

I need to treat a small area ~30 sq ft with foam. Is there a way to do it with cans if SF? Ceiling joist bays. 

I don't like rolled insulation. This is an unheated walk through area.


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## sportbikerider78 (Mar 22, 2016)

Buy one of the small kits for a few hundred bucks and do another area at the same time.


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## maple1 (Mar 22, 2016)

Joist bays, maybe try blocks of foam board cut to a loose fit then seal the edges with spray can stuff.


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## blades (Mar 22, 2016)

Only difficulty with foam boards is possibility of a gap that can allow condensation behind them- that's the beauty of the spray foam no gaps when done right. There several size kits if you dig around some.


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## velvetfoot (Mar 22, 2016)

blades said:


> possibility of a gap


That's why you use the Great Stuff to seal the gap.


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## johneh (Mar 22, 2016)

Tiger Foam kits are the first to come to mind
http://tigerfoam.com/


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## maple1 (Mar 22, 2016)

The foam kits might be good stuff - but that would be a pretty expensive 30 sq.ft.


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## blades (Mar 23, 2016)

velvetfoot said:


> That's why you use the Great Stuff to seal the gap.


Gap I was referring to could exist behind the foam board- between the board and the sill wall not the area around the edges of the board.


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## maple1 (Mar 23, 2016)

*This is an unheated walk through area.*

Does that mean then that you are insulating on the cold side? Has me a bit puzzled.


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## mass_burner (Mar 23, 2016)

maple1 said:


> *This is an unheated walk through area.*
> 
> Does that mean then that you are insulating on the cold side? Has me a bit puzzled.


Yes, on the cold side, I'm attempting to insulate the area above it, a corner of the kitchen.


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## mass_burner (Mar 23, 2016)

(8) 2' and (6) 5' lengths. 16" OC joist bays, 9" deep. ~50sq ft.


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## mass_burner (Mar 23, 2016)

Also, the wall above the ceiling transfers cold into the opposite heated space. This is the stair case wall. I guess I can drop cellulose from the top of the wall into the stud bays.


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## sportbikerider78 (Mar 23, 2016)

blades said:


> Gap I was referring to could exist behind the foam board- between the board and the sill wall not the area around the edges of the board.


I don't think a gap is a problem as long as you have it pretty well sealed off and warm and cold aren't meeting together to cause condensation.  I'd use foam board, sealed into the area with great stuff.    Thats still 10x better than fiberglass insulation from a sealing perspective.


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## blades (Mar 23, 2016)

Just mentioning the problem because there have been some incidents of mold/rot caused by this method - likely due to the sill not being properly sealed from the migration of outside air in the first place- same applies to fiberglass batts with out any moisture barrier  - likely more so as air/moisture does travel through that medium. So when using Fiberglass is of particular importance to get the edges of the vapor barrier sealed.


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## mass_burner (Mar 24, 2016)

How thick should the foam layer be applied? And should it be applied to the sides of the joists?


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## moey (Mar 24, 2016)

Buy a piece of 4*8 XPS and 2 cans of great stuff. Its about $33 for XPS and great stuff is about $3 a can. Cut it about 1/2 smaller on each side where you need it. Youll need to cut some type of wedges to hold the foamboard in place then seal with great stuff. You dont need to worry about the gap behind if you have small ones behind it. You get condensation when a hot surface meets a cold surface not from a gap.


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## mass_burner (Mar 26, 2016)

moey said:


> Buy a piece of 4*8 XPS and 2 cans of great stuff. Its about $33 for XPS and great stuff is about $3 a can. Cut it about 1/2 smaller on each side where you need it. Youll need to cut some type of wedges to hold the foamboard in place then seal with great stuff. You dont need to worry about the gap behind if you have small ones behind it. You get condensation when a hot surface meets a cold surface not from a gap.


Not sure how practical that would be with all the plumbing/electrical running through this particular area. Plus, there are flooring staples poking through from the hardwood floor above.


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## blades (Mar 26, 2016)

mass_burner said:


> Not sure how practical that would be with all the plumbing/electrical running through this particular area. Plus, there are flooring staples poking through from the hardwood floor above.


plumbing and electric penetrations need to sealed as well


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## maple1 (Mar 26, 2016)

mass_burner said:


> Not sure how practical that would be with all the plumbing/electrical running through this particular area. Plus, there are flooring staples poking through from the hardwood floor above.



You'll have to make that call likely - we can't see everything that you're dealing with. Spraying would likely be way easier, just that it would cost more. Is the ceiling already insulated? Could it be sprayed too while you're at it?


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## Warm_in_NH (Mar 26, 2016)

Back to your original post, NO, there really is no way to do a "fan" applied spray foam with the cans you can buy at the store. 
By time you spend the few hundred on the DIY kits, (I've seen this go horribly wrong too, either through operator error or leaks and stuck nozzles, etc...) it's probably at the point where it's worth getting an estimate or two from a company that does spray foam.
There's a lot of things you can do yourself, this really isn't one of them, to do it right requires large vats of chemicals, a high power compressor, proper chemical suits and breathing gear.


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## Seasoned Oak (Mar 26, 2016)

The larger spray foam cans with a nozzle kits work really well. The cans are taller and the nozzle allows you to stop mid -job and save a partial can until you can use it later.  I think the nozzle kit is less than $20.


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## moey (Mar 26, 2016)

mass_burner said:


> Not sure how practical that would be with all the plumbing/electrical running through this particular area. Plus, there are flooring staples poking through from the hardwood floor above.



Thats your call. I just did a cavity/bay in my garage that had electrical in it. Literally last night. I should have taken a picture I guess. It certainly would have been easier to have someone spray foam it but certainly for one bay a waste of money. To work around the electrical I had to cut the foam board length wise and squeeze it in then spray great stuff in the joint between the two pieces. It also took a while to make wedges to hold it tight while the great stuff dried. Its got drywall on top of it now and Im happy I spent the extra time as fiberglass would not have worked very well in this bay given its size and the way the electrical was. 

The flooring staples should not matter I assume they only hang down 1/2 inch or so they actually will help you position the foam rather then having it fall on your head while you reach for something. I did all the rim joists in my basement and they had plenty of nails most I just pressed the foam onto the nail a few I hammered the nail over. 

The DIY kits kinda scare me I guess I just dont like the idea of maybe breathing in something that expands once inside me.


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## mass_burner (Apr 2, 2016)

Evidently, there's a good stuff version called wall and ceiling, but HD didn't have it.


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## Warm_in_NH (Apr 2, 2016)

There's a "great stuff wall and floor" but it's a polyurethane adhesive for gluing stuff to joists / studs.  Almost bought a can the other day, but I decided to let someone else try it first before I made a mess with it on a job.


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## mass_burner (Apr 2, 2016)

Warm_in_NH said:


> There's a "great stuff wall and floor" but it's a polyurethane adhesive for gluing stuff to joists / studs.  Almost bought a can the other day, but I decided to let someone else try it first before I made a mess with it on a job.


So there's no great stuff product for insulating?


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## Seasoned Oak (Apr 2, 2016)

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


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## mass_burner (Apr 3, 2016)

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?


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## mass_burner (Apr 4, 2016)

mass_burner said:


> 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?


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## maple1 (Apr 5, 2016)

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....)


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## mass_burner (Apr 5, 2016)

maple1 said:


> 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?


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## mass_burner (Apr 5, 2016)

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?


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## maple1 (Apr 5, 2016)

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


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## mass_burner (Apr 5, 2016)

maple1 said:


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


You mean my $$ to save?


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## maple1 (Apr 6, 2016)

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.


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## moey (Apr 6, 2016)

mass_burner said:


> 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.


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## Seasoned Oak (Apr 6, 2016)

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.


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## mass_burner (Apr 8, 2016)

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?


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## moey (Apr 9, 2016)

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.


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## semipro (Apr 9, 2016)

mass_burner said:


> 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.


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## mass_burner (Apr 11, 2016)

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?


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## maple1 (Apr 11, 2016)

How high are the bays?


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## semipro (Apr 11, 2016)

mass_burner said:


> 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.


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## peakbagger (Apr 11, 2016)

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.


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## moey (Apr 11, 2016)

mass_burner said:


> 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.


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## maple1 (Apr 11, 2016)

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


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## mass_burner (Apr 11, 2016)

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


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## maple1 (Apr 12, 2016)

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


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## begreen (Apr 12, 2016)

mass_burner said:


> 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.


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## mass_burner (Apr 12, 2016)

begreen said:


> 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?


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## maple1 (Apr 12, 2016)

begreen said:


> 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.


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## begreen (Apr 12, 2016)

I would think there would be less cuts though and a snugger fit with 15" pieces.


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## Highbeam (Apr 13, 2016)

mass_burner said:


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



Most people in the country use fiberglass batt for what you are doing. Sure foam is superior but FG is just fine. You can do a great job with FG in that standard size joist bay. Shop the insulation selection and I bet you can find something that is 10" thick or even 12" thick. It is okay to compress FG, you will only get the compressed thickness R-value. So if you compressed a 9" R-30 batt down to 3.5 inches you would only get R-13 or R-15 out of it. I would rather insulate at R-30 with FG than R-10 with foam.

There is also this mineral wool product called roxul that people like to install as well. 

Why pay the premium for XPS? If you insist on foam, the white EPS is usually about half the cost and just as good.


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## peakbagger (Apr 13, 2016)

If you were close to Maine I would suggest giving Tom In Maine a PM, he sells seconds of insulating foam board for really great pricing.


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## mass_burner (Apr 14, 2016)

Highbeam said:


> Most people in the country use fiberglass batt for what you are doing. Sure foam is superior but FG is just fine. You can do a great job with FG in that standard size joist bay. Shop the insulation selection and I bet you can find something that is 10" thick or even 12" thick. It is okay to compress FG, you will only get the compressed thickness R-value. So if you compressed a 9" R-30 batt down to 3.5 inches you would only get R-13 or R-15 out of it. I would rather insulate at R-30 with FG than R-10 with foam.
> 
> There is also this mineral wool product called roxul that people like to install as well.
> 
> Why pay the premium for XPS? If you insist on foam, the white EPS is usually about half the cost and just as good.


You say SF is superior; but then question why anyone would use it. Can you please explain.


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## Highbeam (Apr 14, 2016)

mass_burner said:


> You say SF is superior; but then question why anyone would use it. Can you please explain.



There are certainly places where foam is superior and is the right choice. Under slabs, thin wall cavities, pipe insulation, etc. but when you can accomplish the same job with other products it is generally MUCH cheaper.

For example, how often do you see open attics insulated with spray foam? Almost never. It is very cheap, effective, and easy to blow in R-50 of cellulose. In that attic floor, foam would have been superior due to air sealing and thickness required but it is super expensive.

In summary. It's about the extra cost for the same R-value when both foam and another product could be used.


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## moey (Apr 14, 2016)

Fiberglass settles which is great for an attic or even a sealed wall cavity. Not good for a exposed ceiling or floor once it settles you have a gap and its R value is non existent.


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## Highbeam (Apr 14, 2016)

moey said:


> Fiberglass settles which is great for an attic or even a sealed wall cavity. Not good for a exposed ceiling or floor once it settles you have a gap and its R value is non existent.



I don't believe either of those claims to be a real issue.


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## moey (Apr 15, 2016)

Highbeam said:


> I don't believe either of those claims to be a real issue.



I can only speak from having a crawl space with insulation hanging it was sagging air was free to move behind the insulation. In our bonus room the R-30 between a floor and drywall of our garage the insulation settled there was about 1 inch gap. Air would be free to move throughout the cavity insulation was dirty indicating air movement in the cavity. When I pulled off the insulation in the rim joists the insulation was filthy again indicating air movement.


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## semipro (Apr 15, 2016)

I have some cantilevered areas of our house where loose fiberglass was blown (packed?) in.  An energy survey later showed that the floors above those cantilevers were cold.  
I opened it up and found the FG had settled leaving a significant air gap under the floor.  
I yanked all the FG (fun job) and installed foam under the floors and then filled the space under the foam with packed cellulose.
If I used batt insulation now it is Roxul or another rock based product.


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## sportbikerider78 (Apr 20, 2016)

If you are looking for used foam board of any kind, look on craigslist.  I have found 8x4 sheets of 2.5" foil on both sides EPS for $12-20/sheet.  I'm sure they are wheelers and dealers as well..come with cash.


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