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Is using spray foam from a can really “best practice”?

tydotten | Posted in Green Products and Materials on

I work for a weatherization company and we use a lot of spray foam cans to air seal these old leaky houses. Fortunately my company also cares about using the products and techniques from a sustainability perspective. I have heard that SPF cans are fairy bad for the environment, but have they do such a good job of air sealing.

My question is: What are the drawbacks of the SPF cans and are the “green products” (like OSI Green Series Pro Foam ii), any better? Is there a product that does the least amount of harm in any significant sense?

Any help would be appreciated and the more detail the better. Thank you.

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  1. user-788447 | | #1

    First read

    If you're going to use can spray foam buy the professional grade reusable gun. Off the shelf cans of spray foam are very wasteful in terms of wasting foam and tossing the containers.

    Also the air sealing ability of spray foam is overestimated in my opinion. I have tested a couple of houses with smoke with a blower door running and seen air escape through the foam. The manner in which the foam expands creates voids and irregularities against the framing.

    Where possible I think using butyl tape may be better for air sealing. Stuffing mineral batt into tight spots is something I am considering in substitution for can spray foam. Would be curious to hear what others think.

  2. davidmeiland | | #2

    I'd be interested in hearing what others think too. I've been using Hilti foam and gun for a number of years, but lately got a batch of cans that wouldn't shut off when removed from the gun... and then my gun clogged up beyond salvage... so I'm between systems right now, but I need something.

    Caulk works in a lot of places, but not if the gaps are large. Backer rod works in larger gaps, but if they're irregular it's pretty hard to make it work. I've had good luck getting canned foam to perform but it takes some practice to get a tight application and not make a mess, and of course it is ideal in irregular gaps.

    Butyl tape... haven't used that for air sealing. Maybe I need to take a look at it.

  3. GBA Editor
    Martin Holladay | | #3

    I'm in the same position as you. I bought a professional foam gun several years ago, but I don't use foam daily. It's very hard to keep such guns from clogging if you're not a weatherization professional. The best way to keep them working is to run foam through them every day.

    So now I have a nice plastic case with a $100 paperweight in it. I went back to $5 cans of foam from the lumberyard. Hey, they work. And if they don't, I can bring them back to the lumberyard and swap them for a new can.

  4. wjrobinson | | #4

    Pro guns need pro gun cleaner run through them. It is a pain if you happen to not do so.

  5. davidmeiland | | #5

    Martin, even with fastidious care I found my gun slowly clogging. The spray cans of acetone that you need to clean the innards are stupidly expensive. I am trying to get my lumberyard to stock something for me, because I hate the cans with plastic straws even more. You gotta have the fine tip...

  6. dankolbert | | #6

    We've never had good luck with the guns either. In fact, we found cleaning them to be counter-productive. The one trick we're never disciplined enough to try has been to take the ones in storage and shoot a little bit every week or so. But I do think the only way for them to really be useful is if they're in daily usage.

    We have broken down and bought ones if we have a job where we know we're shooting a lot. Otherwise we're back to cans and trying to have enough to shoot that we end up with minimal wasted foam.

  7. 72Wendell | | #7

    Finehomebuilding has a video and a small but good discussion on saving spray foam cans.

  8. tydotten | | #8

    Thanks for the responses. Unfortunately this seems to have turned in to a thread about preservation of spray foam guns, which is useful, but doesn't realy help me out.

    J Chesnut: I did read that article and it doesn't really answer any questions about spray foam in a can. If I can assume the spray foam cans are closed cell, they fall in to that high GWP category, but we are using it for air sealing rather than insulation. Butyl tape might work in some applications, but spray foam is way better at sealing gaps in old houses. Both in terms of effectiveness and efficiency of time. We are weatherizing old homes and I have never seen spf affect framing or sheathing enough to negatively impact it's air sealing qualities. We use a lot of spray foam and it's air sealing qualities are fairly rock solid as far as I'm concerned.

    The way I understand this, a large part of the negative impact of the spray foam cans is in the propellant, not the foam itself. I guess I am wondering if the green spray foams help solve the issue of a more earth frienldy propellant or if they just use a little soy and a lot of green washing. I would gladly use the more environmentally friendly foam, even at 3 times the cost, if there is a signfigant difference. If there's not a big difference, as I suspect, then I will just use the $8 a can stuff.

  9. tydotten | | #9

    As far as keeping your guns clean. My understanding is that if you use them with any sort of regularity, you are better off not using the cleaner. Just keep running foam through them and they will last long enough. If you don't use it regularly, you should clean it with that acitone stuff, before it sits for a while.

    If you don't do a ton of foaming, then a can should last you a really long time and save your investmant (the gun) for many years. If you are doing any signifigant amount of foaming, those guns are handy, and you might as well invest in one and a can of cleaner.

  10. user-963050 | | #10

    Couple of points here.

    Spray foam guns are only effective if used on a regular basis. If you allow them to sit for long periods of time, the foam will ultimately cure up because it will take moisture on from somewhere.

    DO NOT USE CLEANERS. Despite contrary logic, cleaners will ultimately ruin the seals on the gun and make that gun cure shut much much faster. The acetone breaks down most of the seals inside the guns and renders them ineffective after a while.

    Here is the simple truth...if you don't use the gun, it is going to cure up. If you use the gun on a regular basis, best practices are as follows:

    -always keep a can that has product in it attached (i.e. if the can runs near empty, run it dry and swap in a fresh can)
    -prior to storage, discharge a small amount of foam and allow that to ball up on the tip and form its seal or if you use plastic tips, allow it to cure inside the tip.
    -store the gun in a relatively static temperature environment so that it does not get subjected to big shifts in temperature/moisture content. If you store the gun when it is cold, the foam at the tip forming the air seal, might not fully cure and be functional

    Do not spend $100 on a gun. The guns that we now use are preferred by the installers and can be bought (albeit in bulk) for about $18 per unit and are just as good as the DOW/Hilti pro guns.

    Tips are less than $0.02 depending on where you get them from and are invaluable for getting into tight spaces and, as mentioned, for great seals at the gun level.

  11. davidmeiland | | #11

    OK, so what are the guns you are now using?

    Maybe I just need to accept periodic gun failure as part of the cost. I probably ran ~25 cans through my last Hilti gun over 4 years. The can stays on the gun if the gun is on the job, otherwise it is cleaned when taken back to the shop, as the next time I need it could be months.

  12. user-963050 | | #12

    Don't clean it. Trust me. Just burns them up faster.

    Email me and I will send you the link for my supplier. They ship and they also supply the nozzles. I don't want to advertise for them on here.

  13. davidmeiland | | #13

    You're saying leave the can on the gun even if it's months? Seems like they will definitely harden up if left that long.

  14. user-963050 | | #14

    Not if the connection is air tight to the can and the tip. 1 part foam is a moisture cure so it should be okay if air tight.

  15. albertrooks | | #15


    In your post #8, you bring the topic back to your original issue which I agree is a really good question: The environmental impact of using canned SPF. Frankly in addition to GWP, I also see the cycle of manufacturing these steel cans that hold such low volumes that in turn just fill a landfill when empty as a really questionable practice. Are you able to put the used cans in a recycle program where you are based?

    I get that airsealing old work is no easy matter and that the most straight forward method is something coming out of a nozzle that can fit and fill odd places and gaps. I agree with JChesnut that moving some application away from SPF to something that has a much smaller waste stream and GWP is a good idea. Tape is a no brainer (to me) when possible, but there have to be manny applications where tape won't work.

    It would be nice to see more positive results and experience in using adhesives and caulks that come from higher volume "material content" to "packaging content" ratios like the sausage bags and sprayable caulk from pumps with more pinpoint delivery tips or nozzles.

  16. user-917153 | | #16

    For sealing certain types leaks in my attic, I used water-based mastic - same stuff you use on ducts. Collin Olson of The Energy Conservatory (manufacturers of the Minneapolis Blower Door) suggested mastic to me, as he'd had success using it on his own home. Apply the mastic by hand with a pair of rubberized gloves to top plates, etc.

    Keith Williams says just because you used foam, it doesn't necessarily mean you've sealed the leak - you still have to test. Keith conducts air sealing training, among other things.

  17. user-757117 | | #17

    Conservation Technology makes an EPDM "gap gasket" that is designed to be pushed into cracks using a putty knife or other straight edge.

  18. davidmeiland | | #18

    Albert, I fully agree with you on the waste created by all this canned foam. It is a real downside of trying to do the tasks that we do with the stuff, and it's just another example of a product where the full cost is not paid by the purchaser at the cash register.

    I like the suggestion of using mastic. In an attic there would be no reason why it couldn't be gooped onto a lot of places that will be buried under insulation.

  19. user-869687 | | #19

    The image below shows windows sealed with mastic outside and in, using packed fiber as a backer. This drawing comes from this interesting study published by the Scottish Government in 2002.

  20. aalden | | #20

    I'd like to strongly support the advice that Eric Novotny has given.
    I've bought a Great Stuff pro gun about a year ago and have run about 5 cans of foam through it since then without need for cleaning anything other than the exterior of the tip.

    Getting to the OP's question: I have found that wasted foam in cans that won't operate has been my biggest problem with the sustainability of using foam. Our local recyclers seem to have no problem with empty foam cans but don't want those still containing product.

    My new strategy for working for insulating with foam is to keep a can hooked up to my pro gun for smaller jobs and then to use the the disposal (hopefully recyclable) single-use cans when I know I can empty them with one use. This also seems to work out better economically.

    As for using mastic, I've also found this to be great for sealing leaks too small for effective use of foam, the seam between adjacent farming members is one place I've used it.

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