# rim joist insulation project question



## dgbehrends (May 4, 2008)

I've done some research and concluded that using fiberglass is not a good solution for rim joist insulation, so I'm looking at following this process 
http://www.rd.com/57548/article57548.html

Are there any problems associated with this type of insulating?

I took a look at tigerfoam and the problem I would have with it is keeping the gun going every 30seconds. I would need to build a platform (to reach the rim joist) all the way around my basement and that would be a lot of work.


----------



## fixrite (Mar 1, 2009)

another option is spray foam from a contractor. I am not sure just how pricey that would be, but it means you do not need to put in vapor barrier as would be needed if you used fiberglass.

cheers


----------



## dgbehrends (May 4, 2008)

Wouldn't spray foam be similar to the tigerfoam I mentioned above. I've come to the conclusion that fiberglass should never be put in the rim joist space because it does not create an air tight seal. If I use extruded polystyrene squares sealed with caulk or an expanding foam spray then I don't need an additional vapor barrier as long as its air tight. Correct?


----------



## fixrite (Mar 1, 2009)

Yes you are correct, sorry I did not read it as thoroughly as I should of. you did not state how much you had to do or if you were up for all the tedious cutting and sealing. With the tiger foam or spray foam it would guarantee you NO leaks and peace of mind. I have an entire house and crawl space that I am going to have to do. I agree with you on the 30 second new tip thing. That would be a pain in the butt. If it were not an entire house to do, then I think you are on the money with the extruded polystyrene calked around edges and foamed for all pipe or other openings.

cheers


----------



## drtbk4ever (Dec 29, 2008)

I would be curious to hear how much a contractor would charge to spray foam?

And is it OK just to leave the polystyrene exposed like that? I was under the impression it would need to be covered with something to reduce the toxic vapors it releases in case of fire.


----------



## SDC (Feb 18, 2009)

drtbk4ever said:


> I would be curious to hear how much a contractor would charge to spray foam?
> 
> And is it OK just to leave the polystyrene exposed like that? I was under the impression it would need to be covered with something to reduce the toxic vapors it releases in case of fire.


As for how much it cost, call a local insulation contractor, they should give you a quote.

Could you tell me what does not release toxic vapors in a fire?
Carpet
furniture
bedding
siding
roofing
vinyl windows
clothing
etc, etc,


----------



## drtbk4ever (Dec 29, 2008)

SDC said:


> As for how much it cost, call a local insulation contractor, they should give you a quote.
> 
> Could you tell me what does not release toxic vapors in a fire?
> Carpet
> ...


Well thank you for the constructive comments. I'll be sure to file that information away for future reference and I am sure the OP has learned a lot about his insulation issue due to your help. I am sure glad we have contractors in here like you. :thumbsup:


Now what I was trying to say is that in some areas, I believe it is against code to leave styrofoam insulation exposed after installation. Whether those same rules apply when using the insulation on the rim joists, I don't know. That is why I threw that comment out there, with hopes that an expert would clarify it for us and the OP. 

Can anyone clarify this?


----------



## fixrite (Mar 1, 2009)

according to CODE... all living areas must have the styrofoam covered with a fire retardant material ( not necessarily fire rated). And this is because although your burning carpet and couch will make you cough and your eyes water, the burning foam will take you down in a much shorter time.


----------



## drtbk4ever (Dec 29, 2008)

fixrite said:


> according to CODE... all living areas must have the styrofoam covered with a fire retardant material ( not necessarily fire rated). And this is because although your burning carpet and couch will make you cough and your eyes water, the burning foam will take you down in a much shorter time.


Well thank you for that information Fixrite. I personally appreciate your expertise and contribution to this topic. I am sure the OP will benefit from your input as I know I did.


----------



## dgbehrends (May 4, 2008)

fixrite said:


> according to CODE... all living areas must have the styrofoam covered with a fire retardant material ( not necessarily fire rated). And this is because although your burning carpet and couch will make you cough and your eyes water, the burning foam will take you down in a much shorter time.


So now the question is:
Is the rim joist area considered a livable area? A simple call to my city's building and safety department would answer this but if I had to guess I would say no and that the foam doesn't need to have an aluminum foil backing. However if foam with a backing is available and it isn't a significant price delta I will probably go with it.

I have between 150 to 200ft of spaces between I-joists to seal. Cutting all these squares and rectangles is not going to be fun. However many of the spaces are hard to get at with pipes and things going into them, plus my rim joist is over 9ft off the ground. If I were to use a foam spray I would need to make some poor man's scaffolding with buckets and 2x6s and even then it would be tough to avoid breaking the 30 second rule.

The cost will depend on the basement size and I think were talking hundreds of dollars.


----------



## fixrite (Mar 1, 2009)

If the rim joist is to remain exposed, you will need to cover it. This is usually done by installing a ceiling. Just a thought regarding the 30 seconds with the Tiger foam, if you had a helper and 2 ladders, then you could simply have your helper mover your next ladder into position while you are on the other one. Leap frog effect. That would allow you to work almost nonstop. Just a thought.

Cheers


----------



## dgbehrends (May 4, 2008)

Having a helper would greatly increase my chances of success. 

It's tempting to go for the foam. I've done a little more searching and have found some more products to consider.
HandiFoam Polyurethane Spray Foam Products and Accessories - DIY Kits
And 
foam-it-green
Foam It Green Polyurethane Spray Foam Kits - Spray Foam Kits

Handi-foam looks to be the same exact product dispenser kit as tigerfoam except the instructions say you have 1minute between sprays.

I kind of like foam-it-green the best because they offer a free tyvec suit and other stuff, but I'm not sure how much time is allowed between sprays. 

Obviously the less time between sprays the better because the longer it sits the more it could expand.

Edit: foamit-green responded to my email question and they said 30 seconds as well. They provide 13 nozzles and a nozzle can be cleaned with acetone so I guess I could switch nozzles when transferring to a spot that would take some time to get the gun pointed up behind the pipes.


----------



## DougDobbs (Mar 18, 2009)

*Experience with Tigerfoam*

I recently used the slo-rise version for an attic floor situation. 1920's vintage house had never had ANY insulation in it whatsoever. It was a lot of work to drill the holes in the pine flooring and squirt all that stuff in there, but what a difference! The occupants said the difference was immediate and dramatic. Hope to put it in the walls one day, but not this year.

I found the "30 second rule" was pretty forgiving with the slo-rise. It was ample time for me to reposition myself and the tanks to make a smooth work flow from place to place in a cramped attic.

I'd definitely recommend two ladders and a helper. You might want to put the foam tanks on some sort of cart so they can be shifted along with you easier as well. 

The cool thing about the foam is that it will expand aroud obstacles like pipes, etc. so just entomb them and move along. 

Do check with your local inspector on the fire protection code issue though. It may make for more work, but if the basement is unfinished and not "living space" then it might be a moot point.

Do tell us what you find out, ok?

Doug


----------



## dave11 (Mar 16, 2009)

I insulated the rim joists in my basement last year, using 2-inch thick Foamular, silicone caulk, and a table saw. Without the table saw, it would be very tedious to have done it, but the table saw and a blade for composites made it pretty easy. Nice straight, quick cuts. I made them snug but not wedged in, because it's important to be able to access the rim joists if needed, to watch for termites, carpenter ants, water/moisture, etc. If you need access, just cut the silicone edging, and pop it out.

Way cheaper than spray foam, and can be removed/replaced when needed. 

Also, Foamular is at least somewhat vapor permeable, while any foil-lined product is not. You don't want to trap moisture against the rim joist or sole plate.


----------



## comp1911 (Jul 20, 2007)

I did a combination of the fitted foam board method and FoamPower spray foam kits in the areas I could not get into to fit foam board.


----------



## jogr (Jul 24, 2007)

You could try to get hold of some drywall stilts so you don't have to keep moving ladders/platforms. Practice moving around with them before you get out the spray foam.


----------



## gma2rjc (Nov 21, 2008)

Regardless of what code says, I don't see why it would ever be okay to leave the foam exposed even in an area that is not 'living space'. During a fire the fumes will easily spread to the living space. Better safe than sorry. 

Having said that, I need to get busy and cover the foam I sprayed in my rim joists 3 months ago :shutup:.


----------



## rtoni (Jul 18, 2007)

This same project is still on my to-do list - but I'm a bit confused (but what else is new) - in a crawl space with foam on the rim joists (either sprayed or board) you need to cover this? there will never be a ceiling in my crawl (30" high). 

How about something like this - foam board (as described in link in the original post) and then a chunk of fire rated insulation (I have bags of Roxul scraps leftover) stuffed in behind that - the foam seals the space, Roxul adds r-value and fire break

Maybe I could even get away with a thin (1") foam board to get the air seal, as the roxul would add quite of bit of r-value itself...?

Does that make sense?


----------



## fixrite (Mar 1, 2009)

you do NOT need to cover the foam in a crawl space as it is NOT considered a living area. The reason is you will not need to escape from that area in the event of a fire.


----------



## Chemist1961 (Dec 13, 2008)

*WAIT look closely*

DG,
I didn't read all the replies but I did all my rim and sill last fall, 1200 ft basement. Since I have no time to drywall the basement I reused fibregalss and will add more as I have time later thsi year.

If you use the foam method you will then need to seal with drywall for fire resistance and toxic fumes.

In your link, your cross vue photo shows a gap below the sole plate and also no sealant above the floor behind your baseboards where drafts are ALSO AN ISSUE.

I pulled my fibreglass and used a bead of sprayfoam along my sill plate, top and bottom, and sides and top of the adjoining joist bays. Then ran another bead approx 8" inward from the wall at both top corners of each joist bay to prevent air travelling inward. Then tucked back the fibreglass blankets. Then I went upstairs and pulled back the carpet and sprayed foam under the baseboards to the sole plate. HUGE difference in drafts and located seriouys gaps in the sill. Also pulled all fibreglass packing around baseemnt windows and replaced with window and door low expansion grade spray foam.

First gas bills indicate at least 10-12 % savings with no added insulation and no other inner air barrier.:thumbsup:


----------



## dgbehrends (May 4, 2008)

Chemist1961 said:


> DG,
> I didn't read all the replies but I did all my rim and sill last fall, 1200 ft basement. Since I have no time to drywall the basement I reused fibregalss and will add more as I have time later thsi year.
> 
> If you use the foam method you will then need to seal with drywall for fire resistance and toxic fumes.
> ...


Here is a picture of my joist bay, 


were you referring to this link? http://www.rd.com/57548/article57548.html


----------



## dgbehrends (May 4, 2008)

I called building and safety in my city and talked to one of the more knowledgeable guys in the department. I know this because I worked with him when I pulled my deck permit last summer. He said that as long as it closed cell that he wouldn't have any issues with it being used in the rim joist bays. He said that either the closed cell foam board or the closed cell spray in foam would work and didn't need to be covered with a fire retarder.

I think I'm going to attempt the foam stuff, I'm not sure if I can get my whole basement done with the 200sq/ft package but we'll see. My uncle has a 4 ft rolling ladder that I could borrow and put the tanks on so that sounds like the way to go. I'll probably wait a few months before I attempt this so that the temperature is warmer in my basement. The foam kits work better the closer to 80 degrees you get.


----------



## fixrite (Mar 1, 2009)

Sounds like you have done your homework. I think I would still do a test myself. I would apply some foam to a small board and ( outside in a controlled environment) see if it caught fire when a flame touched it. I would also want to observe the color and amount of smoke that emitted from it if it indeed did catch fire. Not trying to undermine the guy at city hall, but my life is worth quite a bit to both me and family. Good luck

cheers


----------



## Chemist1961 (Dec 13, 2008)

*foam spray / foam board*

If you settle on one brand of foam go to their site and read about fumes and fire resistance since several of these foams are made of different compositions.
Also remember years ago urea foam was approved and now is not and vermiculite went into attics and now is a problem, popcorn STIPPLE ceilings were made with asbestos,ETC...My point here is that not all city and national codes last. I don't think you should fear the foam but take the precaution. It`s better to be informed before the install and it does sound like you`ve done some homework.

I live in Canada and we had a product here called RetroFoam which was distributed locally.I think it originates in the states. After being approved by the FEDERAL GOVERNMENT AND BEING ALL OVER THE NEWS AS AN ENEERGY SAVER, LAST MONTH THE GOVERNMENT RETRACTED AND PUT THIS GUY ON HOLD AND ARE RE EXAMINING HIS PRODUCT.

My rule of thumb is this If you wouldn`t make a camp fire and cook a hot dog over it you don`t want to ever have those items at risk of burning in your home.

Either way, good project, good effort. By the photos I`m guessing your house is newer so it should be better insulated under the sole plates than mine and likely prewrapped with tyvek or similar however I was amazed at how many cold pockets I found with a thermal scanner particularly around baseborads and inside corners at closets and partition walls.

Keep us posted.


----------



## Chemist1961 (Dec 13, 2008)

*foam spray / foam board*

The gap I referred to was the cross section from the how to site. I prefer to start the sealant right at the rimjoist and seal all points of contact of adjoining joists. Might be overkill but it works. In your case if you spray the whole joist bay the foam will travel there anyway.


If you settle on one brand of foam go to their site and read about fumes and fire resistance since several of these foams are made of different compositions.
Also remember years ago urea foam was approved and now is not and vermiculite went into attics and now is a problem, popcorn STIPPLE ceilings were made with asbestos,ETC...My point here is that not all city and national codes last. I don't think you should fear the foam but take the precaution. It`s better to be informed before the install and it does sound like you`ve done some homework.

I live in Canada and we had a product here called RetroFoam which was distributed locally until last month. I think it originates in the states so you might want to read up and see if there is any further news relating it to similar products you are considering. 
After being GOVERNMENT approved and making the local news as a great new product and business venture, LAST MONTH THE GOVERNMENT RETRACTED AND PUT THIS GUY ON HOLD AND ARE RE EXAMINING HIS PRODUCT.

My rule of thumb is this If you wouldn`t make a camp fire and cook a hot dog over it you don`t want to ever have those items at risk of burning in your home.

Either way, good project, good effort. By the photos I`m guessing your house is newer so it should be better insulated under the sole plates than mine and likely prewrapped with tyvek or similar however I was amazed at how many cold pockets I found with a thermal scanner particularly around baseborads and inside corners at closets and partition walls so check those areas when you`re done the basement.

Keep us posted.


----------



## dgbehrends (May 4, 2008)

House was built in 2004, and this winter when it was -30F out I went around the basement with a can of great stuff and felt for air leaks with my hand and sealed up a bunch of places. There are still smaller leaks that could be sealed which is why I wanted to just seal the whole rim joist bay area. 

The spray foam I'm leaning towards, is named foamit-green.
http://www.sprayfoamdirect.com/

My second choice would be tigerfoam, followed by handi-foam.

Next winter I plan on renting an IR camera. I've gotten some quotes and it would cost me about $250 for 2 days. If I didn't plan to raise my kids in this home I probably wouldn't go through all this trouble :wink:

I appreciate all the thoughtful advice people have given :thumbsup:


----------



## Chemist1961 (Dec 13, 2008)

I don't have the IR camera but borrowed a heat sensing laser temp scanner from a furnace guy. I think the IR scanner would be great on finished walls but my guess is you will be fairly consistant if you scanned your rim joist especially in new construction given improved codes. 

I detected big leaks around heat ducts travelling up outside walls, and perforations for AC and electrical to outside, but bay to bay the joists were very consistant. In my case it was sole plate on concrete where the big gaps were, in corners and around windows. I had no tyvek on the rim joist, just brick or stucco outside. Also any abutting concrete porch area is suspect as a heat sinc.

Just my opinion but you would have to find a hole the size of a football to offset that $250 rental and that seems less likely in a 5 year old home.

If you are going that distance, why not get a complete energy audit done by a guy with camera.

I had an audit done for leaks, then scannned with the thermo laser myself a month later, but again my house is 35 years old...and the leaks I found wouldn't need the camera.


----------



## dgbehrends (May 4, 2008)

I did have an energy audit done about a year ago that included a blower door test and some IR camera pics. My house is 4000sq/ft and he didn't spend the time I would with the camera looking for leaks. You are right about the payback in years, to recoup the cost of an IR camera rental I would have to find something quite large. I think I've gotten all the big stuff between my own testing and the energy audit, but I've got this perfectionist habit that is hard to kick when it comes to this kind of thing  If I do the IR camera it will be in the middle of winter next year after the spray foam is applied. I will be able to cover every sq/ft of my home 

After I do the foam this summer I'll post another pic.


----------



## dgbehrends (May 4, 2008)

*sorry for the thread necro*

I'm finally getting to this project. With the energy credit running out I was compelled to buy a several 4'x8' sheets of R10 2" closed cell foam board and a bunch of great stuff cans. Tomorrow is the day I tackle it. I'll make one final post with the results and maybe a picture.


----------



## gma2rjc (Nov 21, 2008)

I'd like to see some pictures and hear about how it goes. I've been working on getting my house sealed up for a couple years and I have the same 'problem' you have as far as being a perfectionist. I keep looking for more ways to keep the weather out.

With all I've done so far, I brought my heat bill (gas) down from $131 per month on the local gas company's budget plan, to $54. But I'm not finished yet. 

Are you still planning on getting the IR camera? If it's that expensive, you could always find someone who will go in on the cost of it with you if they want to use it in their house.


----------



## dave11 (Mar 16, 2009)

dgbehrends said:


> I'm finally getting to this project. With the energy credit running out I was compelled to buy a several 4'x8' sheets of R10 2" closed cell foam board and a bunch of great stuff cans. Tomorrow is the day I tackle it. I'll make one final post with the results and maybe a picture.


 I did all my rim joists a couple years ago, but didn't use Great Stuff. If you ever need to remove the foam blocks, to inspect for termites/carpenter ants, or moisture, I think you'll regret it. I just cut the foam to fit tightly against the rim joist--the foam block has some "give" to it. For the few areas that weren't tight, I used silicone caulk.


----------



## Chemist1961 (Dec 13, 2008)

This issue of access is why I avoid the closed cell board in some areas along the rim, but the rim joist still breathes with plain rock wool. 

My bigger issue is the one wall running 25 feet where the rim and the first joist are only 3.5" apart. 
the only access I have is to section reflective, rigid foam and tuck it above and back against the joist. I cannot seem to reach my foam gun deep enough to seal above the sill plate and at the top where the rim meets the underside of the floor, so I may resort to silicone globs on the tip of my gloves and smear the wall. If anyone has flex tube extension or similar for a foam gun please let me know.

I too have lowered my gas consumption substantially, over 35% and counting from the total project so far and am now boarding the walls with R10.5 closed above grade, R10.5 open cell below and then will cover with r13 mineral wool, fireproof. I have read on buildingscience .com that this hybrid technique will allow the walls to breath. Much more expensive this way but I lucked out materials at 1/2 price at a building center which was closing.


----------



## rtoni (Jul 18, 2007)

I was also asking about this when this thread was originally posted. I ended up doing essentially what Chemist talked about - a bead of Great Stuff along all the inside corners within in each bay (top, bottom, both sides, as well as 6 - 8" "back" along the underside of the subfloor and the top of the sill plate). Then a clean cut piece of Roxul (R22) in each bay. 

I checked them recently (going on 2 years since then) and when I pulled the roxul in a few spots it was clean and dry (did this last year and this year too). Overall very tedious work but a couple bags of roxul and a few cans of great stuff was under $100 to do @1000 sq ft. 

Chemist this is probably no help to you but I made a "poor man's" foam gun when I hit the tight spots in my crawl space (could not get access with a regular can - I had no gun to begin with). Ok - don't laugh - I had a few feet of clear tubing leftover from another small project - might have been 3/8 "..? Anyway I slid this over the end of the plastic straw that comes with the great stuff cans (a very tight fit - about an inch or so is all I could get). Then taped a very small diameter piece of dowel near the end, and used that 20" or so contraption to get the end of the clear tube right into the tight spots. It held up - crude and a bit messy (no perfect bead or anything) but it did the trick.


----------



## Earnie (Jan 24, 2008)

I was looking at having my rim joist spray foamed, but you guys have me questioning that decision. Foam would have been just 1" thick to seal the area. Over the foam I was planning on R13 Roxul.

So its best to just air seal the wood contact areas (mud sill, rim joist, sub-flooring and floor joists), then batt insulate? 

RToni - Are you saying that you used can spray foam and sprayed the underside of your sub-flooring? Is there batt insulation over the foam? Faced or unfaced?


----------



## rtoni (Jul 18, 2007)

Earnie said:


> I was looking at having my rim joist spray foamed, but you guys have me questioning that decision. Foam would have been just 1" thick to seal the area. Over the foam I was planning on R13 Roxul.
> 
> So its best to just air seal the wood contact areas (mud sill, rim joist, sub-flooring and floor joists), then batt insulate?
> 
> RToni - Are you saying that you used can spray foam and sprayed the underside of your sub-flooring? Is there batt insulation over the foam? Faced or unfaced?


I really need to get a camera to make up for my bad descriptions :yes:

Essentially I went into each bay with the can and any corner where framing members meet (the floor joist meets the rim joist / sill plate / subfloor) I ran a bead of foam, including where the top of the joist meets the underside of the subfloor. Once it was sealed in the corners, I cut a piece of the R22 Roxul to fit snug in the space. Very easy to remove and inspect, which I've done a couple times now in random spots.

If I had a big bag of $$$ I would have called the spray foam guy in a heartbeat too, but I didn't have the budget for it. The pro's might say that's still the best way to go (seal the rim joist completely inside) and as a DIY who am I to argue. I saw the tanks of DIY foam stuff show up on a rack in the local bulding supply - I thought "great" - but then saw the almost $500 sticker and walked away. So if you have some time and don't mind the tedious aspect, a poor man's approach is much easier on the wallet and might work for you. After reading a lot of discussion here I gave it a try and so far so good. Just adding my 2c to let you know it seems to work well for me but there's lots of good discussion here IMHO to help you decide...


----------



## Earnie (Jan 24, 2008)

Now I'm really confused.

Is it really necessary that you periodically look at the rim joist for moisture issues? Probably nothing wrong with looking, but once you seal the area (full spray foam, foam board, or just caulk) shouldn't that be it?


----------



## rtoni (Jul 18, 2007)

Earnie said:


> Now I'm really confused.
> 
> Is it really necessary that you periodically look at the rim joist for moisture issues? Probably nothing wrong with looking, but once you seal the area (full spray foam, foam board, or just caulk) shouldn't that be it?


seems to be what I do best (confuse people) - as you can see by the threads here and elsewhere there's a lot of discussion and a few different approaches to solving this problem. add to that the fact that I am a DYI'r - so sanity checks are the norm for me and this is a really really easy sanity check. In the 5 minutes it takes (literally) while I'm in the crawl space working on something else I can pull a few random chunks of insulation and take a quick peek in those spots - not everywhere - hope that's not what I implied). A random check - and if there is a problem (like moisture) I catch it and deal with it. I'll do this a couple times a year for a couple years (let the house cycle thru a few seasons) so I really know it's working for me. It just helps me sleep at night.


----------



## Earnie (Jan 24, 2008)

Thanks rtoni.

I completely understand your wanting to sleep peacefully knowing the rim joist is not rotting away.

I was only looking for the scientifically approved method. Maybe there isn't one. 

I don't want to find out six months later that the building code now say NOT to completely seal the rim joist area after I just spray foam sealed it.


----------



## rtoni (Jul 18, 2007)

no problem - guys who've done a hundred of these can probably offer better advice on what works best or may be required in your area / circumstances. I figure in my case if my approach bombed, I haven't painted myself into a corner, so to speak - it's not a fortune invested and I can easily undo it all even in the worst case (pull the roxul out and / or add rigid foam board, spray foam everything, etc.). Things to consider IMHO. I guess you can say I took a bit of a chance (a bit of time invested) and it's working out - so now just offering up that experience fwiw. Good luck with whatever you end up doing.


----------



## wilsonstark (Jan 16, 2011)

Just finished insulating the headers with 2 layers of 2" XPS (I used formular c-200), sealed repeatedly with silicone and sprayfoam. I found that unless I left VERY big gaps between the XPS and the joists, the spray foam bead wasn't 100% air sealed. It sticks to the xps pretty poorly when first dispensed, and about 1/2 of the narrowest beads I did ended up useless (with holes allowing air to pass through). I ended up using silicone to seal, which is tiresome but worked great in the very small gaps as I cut it. It was a huge pain in the butt cutting tight little rectagles on the two walls that meet the joists (they look identical, but they're not). They are warm and dry right now during the nasty cold snap we're getting in Ontario at the moment, so I guess I should be happy 

If you're looking for fast, I'm guessing the guy who did sealing and Roxul is laughing, assuming the air sealing worked out well. I'm proud of the work I accomplished doing two layers of c-200, but it was a lot of time. I wish I'd read the trick about using a table saw with special blade to cut xps before I started. I did everything with straight edges and very sharp utility knives and that sucked...

BTW, you need to check the adhesive you're using if you're doing two layers of formular. RONA has contractor tubes of PL300 for the first layer (affordable), but when you're sticking XPS to XPS you can't use PL300 and you end up having to buy the more expensive PL9000 (which I could only find in the smaller tubes).

To be honest, I liked PL9000 better anyway but it's costly. PL300 requires the board be mechanically attached while it cures, which gives you an extra job to do later on, since screwing it in place with a washer or bit of strapping is okay, but the screw is a thermal bridge you're going to want to remove later and fill the hole with foam.


----------



## ThatDaveGuy (Dec 31, 2010)

Man, you guys are killin' me. Part of the plan for upgrades this spring included budgeting for a spray foam kit specifically for this, the rim joist in the crawl space. Now I read through this thread and apparently that all needs to be rethought, as if Gary's damning indictments of OSB weren't already enough. :laughing:


----------



## wilsonstark (Jan 16, 2011)

ThatDaveGuy said:


> Man, you guys are killin' me. Part of the plan for upgrades this spring included budgeting for a spray foam kit specifically for this, the rim joist in the crawl space. Now I read through this thread and apparently that all needs to be rethought, as if Gary's damning indictments of OSB weren't already enough. :laughing:


Not sure there's a formal downside to spray foaming them. I would have done that myself but couldn't afford it.


----------



## Earnie (Jan 24, 2008)

I just had the crawlspace cleaned of mold so now the rim joist project is quickly approaching.

What exactly is the point of installing the foam board if you plan to insulate over it? Couldn't I seal the rim joist wood contact points with silicone caulk then cover with Roxul? Silicone would seal the air infiltration points and the Roxul would provide some insulating value.


----------



## ThatDaveGuy (Dec 31, 2010)

wilsonstark said:


> Not sure there's a formal downside to spray foaming them. I would have done that myself but couldn't afford it.


Understood, but when I hear comments about access to check for moisture and insects if just makes me stop and rethink one of the things I thought I had settled. But then, that's why we're here, isn't it?


----------



## wilsonstark (Jan 16, 2011)

ThatDaveGuy said:


> Understood, but when I hear comments about access to check for moisture and insects if just makes me stop and rethink one of the things I thought I had settled. But then, that's why we're here, isn't it?


Yes indeed


----------



## rtoni (Jul 18, 2007)

wilsonstark said:


> Not sure there's a formal downside to spray foaming them. I would have done that myself but couldn't afford it.


Amen - tripping over a bag of $$$ would have brought it all down to a phone call, like so many other projects - but necessity is the mother of invention. Saturday's outside temp here (also in Ontario) - a balmy -34 deg. A good day to find any spots I missed I suppose. Wood stove heat - and overall the (unheated) crawl space has stayed above 46 deg. I suspect this would have been a big freezer without the insulation at the rim. No regrets.


----------



## wilsonstark (Jan 16, 2011)

rtoni said:


> Saturday's outside temp here (also in Ontario) - a balmy -34 deg. A good day to find any spots I missed I suppose.


Yeah, it was awesome to have it that cold, at least for these purposes. A few missed spots were distressingly obvious with such a raging temp differential


----------

