Rigid foamboard damaged by nails in rim joist
I began insulating the rim joists in my 3 year old home, climate zone 5, using 2″ rigid foam board insulation. Each board is glued in place with construction adhesive (compatible with foam board) and I am filling the perimeter with canned spray foam (GreatStuffPro) from a dispensing gun. I am running into two issues:
1) There are nails, installed from above and outside the rim joist (sharp edges pointing into my working area) that are damaging the foam as I test fit and install. It is creating compressed/torn pockets in the foam. Is this a problem?
2) There are some areas where I cannot get the GreatStuff foam around thebperimeter as I would like. Given the shape of the dispensing gun and the shape of some of these cavities, I cannot get the nozzle in far enough to lay the foam directly on the joist… I suspect there are various air pockets encapsulated between the sil plate, rim joist, rigid foamboard, and GreatStuff. Is this a problem?
If I had to do it again, I probably would have bought a 200 board foot closed cell foam kit and used that. I am only about 20% complete so I may abandon the rigid board and buy the kit. My foundation has about 150 linear feet of rim joist I can insulate. Most of it is exterior but some of it faces my garage
How should I proceed?
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Replies
Get a piece of clear flexible tubing that fits tight over the end of your gun from a hardware store, that will solve your access problem.
I wouldn't worry about the nails but if they concern you, just bend them over with a hammer.
The spray foam kits work really well, but they are tricky to use for the first time. Getting the thickness and coverage right is kind of an art. But hey, only one way to learn!
Thanks for the reply! I tried a piece of tubing, which was included with my gun, and it worked great on the first pull. I stopped for maybe 10-15 seconds to move the ladder and the foam began to thicken enough in the tube so that the pressure from the gun made the hose pop off the tip of the gun. I might try a disposable can for the stretch of problematic area which has a floor joist running parallel with the wall. Still, I am not confident, even with the can, that I can get GreatStuff foam all the way to the wall consistently.
Here is a pic of the small space I have to work with.
You need to bleed off small amounts of foam as you go if you aren’t ready to just go foam foam foam in one big shot. It’s best to pin up enough foam panels that you can just go from one to the next until the fan gets empty, then put up more foam panels, put in a new can of spray foam and do the next batch. If you wait too long between blasts of foam the tube will clog up. The gun can clog up too if you’re not careful. I always keep a can of acetone handy and some paper towels, and I wipe the tip of the gun every time I have to stop foaming for more than a few seconds.
Pounding over the problem nails shouldn’t cause any problems. If you have a few holes pop out in the foam panels, just squirt some canned foam into the holes to seal them up. Easy.
In that tight spot, a two part spray foam kit is probably your best option. I’d use the kit in that tight spot, then use whatever of the kit is left to foam in place more foam panels in other areas.
BTW, sometimes a can of canned foam — they kind of can that has its own tube and doesn’t need a gun — can get places where the gun can’t. The biggest problem with the gun is the can screwed into the top gets into the way. When I have a big job to do I do as much as I can with my gun but I always keep a few “self contained” cans handy too.
Bill
Thanks, that all sounds great! So when I get the polyurethane spray foam kit, can I blow a thin layer of insulation over the 2" foam board + mediocre GreatStuff sealing job in my long trouble spot, or does that 2" foam board + GreatStuff have to come out? I feel pretty good about the board but I have no way to tell if the GreatStuff I am installing is adequately air sealing around the foam board. A thin layer of polyurethane spray foam over the whole thing would seal it up but potentially trap pockets of air/dead space underneath it.
You can spray foam over the foam panel + greatstuff assembly. What you need to make sure it is that you do NOT want any airgap between the rigid foam and the wood — If the foamboard isn’t a tight fit against the wood, you should replace that piece. I usually just push on the foamboard a little and check for springiness. No springiness = tight fit.
Note that the temperature of the canisters on those spray foam kits is critical. Commercially I have my guys leave them on a transformer overnight the day before the installation. This usually get the canisters uniformly up to around 80-90 degrees or so. On a small residential project, we put the cans in a bathroom with an electric heater running for 3-4 hours before the application. You NEED those canisters to be WARM. Not crazy hot, but WARM. If you don’t have them warm enough you’ll get much less foam than you should. If the canisters cool off too much during use (and they will cool off from expelling the foam materials); you need to warm them up again. Usually if you have them warm enough before starting the job you won’t have any problems with them cooling off too much except maybe with the 12 board foot kit.
Every time you stop for more than a few seconds, you need a new tip. Set up and plan your entire job so that you can start foaming AND KEEP FOAMING until the entire job is done. This includes clearing any obstacles, setting up lighting, etc. keep some paper towels and acetone handy. Wear a full tyvek suit with booties and a good, safety glasses and a mask. You’ll get foam all over so you need the safety gear to avoid getting foam on yourself. Mask off any areas you want to protect too since the foam “mist” will get on nearby objects and it is a huge pain to remove. It really, really sucks if you get any in your hair too so be careful.
Start foaming in an easy area that is not too obvious since you’ll be messy when you start while you learn the feel of the setup. It expands a lot, so don’t dwell too long in any one spot — always keep the gun moving in a smooth pattern. Don’t go too thick in one pass either, 2” of EXPANDED foam is usually about the max for the kits.
Bill
I am using 3/8" vinyl tubing (https://www.amazon.com/gp/product/B0046ECKY0/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1) as Yupster said, to get into the nooks and crannies. My gun has a tip on it, then the vinyl is snug over the tip. I cut the vinyl to 12-18" long, depending on need. You want to have the gun oriented so the can is plumb upside down at all times.
If you want some tips for maintaining a gun well and getting good results, here are some old but well done videos from Todol: http://www.todol.com/training-videos/gun-foams-system-overview/
Make sure you leave a pressurized can on the gun at all times and squeeze out some foam at least every 30 days.
I forgot to mention, I dealt with the nails by grinding them off with a dremel prior to gluing in the polyiso and then foaming around the edges.
Thanks so much for all the info. Tons of helpful tips and ideas.
A critical distinction... Airgap behind the rigid polyiso panel is bad but airgap behind GreatStuff is acceptable? Or does GreatStuff with airgap behind it need to come out? All of this would be covered by polyurethane foam.
I am pretty excited about buying a kit and giving it a shot. Any suggestions on brand? I am leaning toward the 200 board foot Foam It Green kit from sprayfoamkit.com. The insulatable perimeter of my basement is 150 linear feet and the joist is about 11" tall. After spraying, I would likely reinstall the fiberglass batting that was installed by the builder.