Having Spray Foam installed on basement cement block in colder weather
We are remodeling a house in Climate zone 7 in northern Wisconsin that has extensive damage and odor issues from cats.
We were planning on spray foaming the interior of the basement cement block walls after framing for 2×4 walls 3 inches out from the block. Basement has a west facing side that is above grade. Due to timing issues, our slab (over EPS and old slab) might not be poured now until late September and framing might not be up until early October. We really need it insulated before winter.
I am worried that the block will be too cold for good spray foam adherence in October. One Spray foam contractor says he has a BIG heater they can run for a few days before foaming but I am skeptical that any heater could change the block temp that much.
I also worry about the excess moisture that will surely still be in the building from the slab pour.
I might be able to get the cement block walls spray foamed with just 2 inches in early September before the slab is poured and have them come back after I frame to complete the 3.5 inches of total foam.
1. Is a 3 inch gap from the wall to the framing too much for the spray foam? I plan to have 3 inches of GPS foam on the slab edge and I was going to leave the foam sticking up a few inches and use that as my framing offset guide. I wanted the spray foam to match that and connect to the framing slightly.
2. If they spray 2 inches on the cement block wall and come back later for the final 1.5 inches, are there any other issues I might have? Even if they can’t come back until spring or it takes me longer to get it framed, 2 inches is SO much better than zero.
3. I could bring the slab edge GPS 2 inch foam board (outer most GPS slab edge layer) up the wall leaving only 12 inches of block bare at the top. Later I could have them spray foam the top of the wall, the rim, and add 1.5 inches of spray foam OVER the entire wall and GPS. I am hoping this will still be a good air and vapor seal for both condensation prevention and any remaining cat urine odor. I would use the same framing plan. This would make it easier to remove the foam later if there were adhesion issues and spray foaming to foam would probably work better than spray foaming to cool concrete.
What is the biggest downside to spraying 1.5 inches over the GPS and not having the foam directly adhered to the block wall? Is it so much better to spray directly on the wall that I should not think about the GPS board idea?
4. If I do spray foam over the foam board, are the taped foam board seams an issue for spray foam adherence?
Thank you in advance for any professional insights.
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Replies
There is no point to applying spray foam over the GPS. There really isn't much point to using spray foam here at all. I would just use the GPS alone for ALL of your R value, and if you use any spray foam, confine it to the rim joist area alone. On a basement wall with a reasonably flat surface (block or concrete both quality in nearly all cases), rigid foam board alone is an easier, cheaper, and greener way to go.
You don't really need to frame out a full interior wall, either, you can go "on the flat" and save some space (and material). Don't be thinking about using batts in the wall for additional insulation, either -- you're much better off just using a thicker layer of rigid foam.
BTW, spray foam adherence to surfaces suffers in low temperatures and excessive moisture content of the surface. I don't think you're likely to heat up a large basement wall much with a heater, so I would be concerned about good adherence in very cold weather. That's not an issue with foam board, but it is with spray foam. It's probably still possible to do the job, but if you're set on spray foam, I'd very much try to do it before things get much below 50*F or so, otherwise consider waiting until things warm up again in the spring.
Bill
Bill,
It is nice to know that my concerns and thoughts were not totally off base.
The main reason for even thinking about spray foam is due to the fact that the original owner’s (30 plus?) cats actually used the half finished basement ceiling as a litter box (attic as well , but I will have questions on that project later). Urine ran down the block wall in the basement. We tried about 17 different methods to eliminate the urine odor and even though it is 95% better, we thought spray foam might work for everything. Air sealing, condensation control, and remaining odor control. Until I read about possible application range issues with spray foam. It looks like a big job to clean up if it does not adhere well.
My thought on spray foam at the rim and over and around the GPS was just as an added air and vapor barrier. It seams hard to get a good seal everywhere with foam board.
I do appreciate that the foam board has a wider application range than the spray foam.
I did wonder if foam board was really still effective in block walls vs the smoother poured walls, so thanks for answering that as well.
So my basement insulated with foam board (with careful installation) should provide results similar to spray foam in energy savings?
Jay
Bill,
After thinking more about your response, I have two foam board on cement block wall application questions.
What do you recommend as best practice between non tongue and groove foam boards on basement walls? Do you like to foam the seams, use adhesive in the seams, or just tape them if using over lapping layers of foam?
Do you use adhesive like PL to put up the foam and attach one foam layer to another? Or Fasteners like tapcons or the plastic tap ins? Or do you use a combination?
Thanks,
Jay
Try "Urine Destroyer" by Nature's Miracle. It works quite well on cat urine (they also make a version for dogs). Use a UV flashlight to find the spots that need to be trated -- cat urine lights up under UV light.
I usually use square edge foam board for basements just because it's easier to get, but T+G is better if you can get it (or can wait for a special order to come in). I normally tape the seams, but sometimes I'll inject canned foam. It depends what I'm doing when I decide which way to go. Tape is easier though, and gives a cleaner end result. You just need to make sure the tape stays stuck. If you're using random foam board, I use Nashua 324A foil tape for foil faced polyiso, which is overkill but works well and looks good when done. I use a wide (3+ inch) tape made for use with polyethylene crawlspace liners on XPS. I usually use canned foam on EPS, but tape works too. The issue with tape on lower density EPS is that it has a tendency to pull apart the beads that make up the EPS panels if you apply any stress to the taped joints.
To attach the foam board to the walls, I like the tap-in plastic anchors like those made by Plasti Grip:
https://www.amazon.com/Plastic-Masonry-Fastener-250-pcs/dp/B00IMG3L4G/ref=sr_1_3?keywords=PLASTI-GRIP&qid=1691116787&sr=8-3
Just drill a hole through the foam board into the wall with a rotary hammer, insert the anchor, give it a whack or two with a mallet and you're done. It goes fast, it's reliable, and it doesn't make much mess.
Bill
Bill,
We have powerful UV flash lights in a few slightly different wave lengths for finding fluorescing rocks, and they definitely helped track down urine stains in some areas. We found them somewhat ineffective on concrete though, especially the block. We could often smell the urine strongly in areas of the block that did not fluoresce at all. Maybe soaked in too far? We also found out, many other things can fluoresce as well. So, although they helped, I guess one really needs to know how to interpret the findings.
Unfortunately Nature’s Miracle was the first product we tried. We tried multiple applications with larger and larger volumes (including pouring right onto the floor) in both the basement and on some affected studs and subfloor on the main floor. If it helped, it was not noticeable. I am not saying it is a bad product or that it doesn’t work, I am guessing that the amount of cat urine and the years of saturation made it impossible for any enzyme based product to be effective.
We tried 3 other enzyme products with Enzyme D being the one that seemed to make the most difference but still not enough to declare any sort of victory. That one also required more personal protection during application and could also be used full strength to eat through drain clogs.
We then paid a friend who does mold, fire, and flood remediation (with certifications) to come in and try several different things including special canisters and some type of special peroxide (not 100% sure on that) spray that bubbled on contact. Odor elimination results were still very lacking.
So far, the only success we have had with the cat urine odor, involved sealing or removal.
We removed and replaced the sill plate when the house was lifted because it was so saturated with cat urine. I wish I had been reading GBA then because I would have had the contractor (only house lifting contractor in area so not many choices) seal the sill differently. I now know that, “that’s the way we have always done it and never had an issue,” can mean that a contractor may have stopped learning and improving.
We then coated the floor joists (they were also soaked with urine) in the basement ceiling with shellac based BIN. We tried both Kilz original oil based and BIN upstairs in a few areas and BIN was better at sealing off the odors in our case. We were very satisfied with the BIN results.
We also removed and are replacing the top layer of the two layer subfloor in some of the upstairs areas. Even after BIN in those most saturated areas, we could still smell the urine smell. Removal solved the issue of course.
For the walkout basement concrete, we ended up using a concrete sealer from Bone Dry in Kenosha, WI. It is NOT marketed for odor sealing but provided satisfying results. We were NOT using it for any type of water intrusion or other issue so we can’t comment on their other claims. We did a “water saturation” (porosity I guess?) test after speaking to the manufacturer and did not need to etch the concrete before application. We did use their primer product first. Application was SUPER easy. We used two separate pump up garden sprayers.
The floor is being insulated with 3 inches of EPS and poured over so that should resolve any remaining urine issues from the old slab. Hard on the budget but will be good on the nose and nice on the feet in winter.
Thank you for the link to the plastic tap in foam board anchors. Those are the ones I remembered seeing elsewhere but I had no idea what they were called. How many should I use per sheet? I hate the idea of having too many holes in my block walls. Don’t I also need sealant between the foam and wall to help prevent airflow?
For multiple foam layers what do I use to attach the outer layer of foam to the inner layer? The same stuff? More canned foam or foam adhesive in a tube?
Even though you did not see the value of the spray foam over the foam board, I am still wondering if that would provide a superior air seal vs taping of the outer most foam layer, the sill, and the rim.
Thanks,
Jay
Note that Nature's Miracle is the brand, and they make several products. They make one for drool and barf (which is the one I was most familiar with), and another called "urine destroyer". Urine destroyer worked MUCH better for me than the drool+barf cleaner. It sounds like you have a very serious issue though, so it's entirely possible there is just so much urine, soaked in so far, that the cleaners can't penetrate enough to get it all. I had one corner with a lot, but after 3-4 total saturations, it worked for me.
You don't need to air seal behind the foam board, because the foam board itself is an air barrier that seals the entire backside of the board off from the living space. You only need an air barrier between the living space and the "outside", you don't need to seal between different layers that are outside of your building envelope. In this case, I don't see spray foam adding any benefit, because the only places to air seal are seams between sheets, and the perimeter of the sheets (especially the rim joist area). Tape works fine on the seams, and you can use canned foam in the other areas. The rim joist is one area where spray foam is sometimes the best option, since spray foam makes it relatively easy to seal complex structures where there are lots of obstacles that would otherwise be difficult to seal well. You gain nothing in terms of air sealing by putting spray foam over the surface of the foamboard, since the board itself is a very good air barrier.
I would lay multiple layers of foamboard and then run one anchor through the entire stackup if I could get a long enough anchor. I might use a small number of "interior anchors" to anchor the inner layer for easy of installation of the second layer, but that would depend on the work area. I've never really bothered to seal the anchors themselves, they tend to be a tight enough fit in the holes that I haven't really been concerned. Foam board, when drilled, tends to be "squishy", and not really drill cleanly. This helps it seal around the anchor, since the squishy foamboard acts like a gasket around the shaft of the anchor.
Bill