Monday, December 28, 2020

3 Problems You Will Run Into With Spray Foam

There are five things that this wall behind me is doing right now. It's keeping the roof off my head. It is keeping out moisture, it is keeping out air, it is controlling heat, and it is controlling vapor drive.

Today, I'm going to talk about spray foam and its amazing ability to keep out heat and air. Everybody knows that spray foam is a good insulator, it has a high r-value if installed correctly, and it can also be a good air barrier. It would help if you looked for a few things to make sure that both of those are done as well as they could be on a Spray insulation job, so first, you want to make sure that your required thickness for your insulation value is there. 

The spray foam doesn't have to be full cavity depth, meaning you don't have to overfill the cavity and then come shave it back off, especially if your thicker stud R values are lower. 

You only need four inches of insulation, and you've got a two by six. You'll have some insulation that is just bubbly texture on the front if it's not shaved off, even if it's to the right thickness. The problem with an under-filled cavity is it's hard to tell if any spots are underfilled if you went all the way to full cavity thickness and then shaved it. 

The second thing that this spray foam insulation should do is keep air from infiltrating into the house. At least that was the case in their original design. This is a house that we have taken over mid-construction. They were putting cabinets on the wall, but we've ripped off all the exterior cladding and interior and are redoing it. We found several places where this spray foam is underfilled and pulling away from the studs. 

So if that spray foam is pulling away from the studs in the same place that you have a seam in your sheathing and the exterior sheathing is not taped or doesn't have a fully applied membrane of some sort keeping out the air, then your air will leak right through that hole in the gap in the sheathing and then right through the gap between your stud and your spray foam.

There's a ton of variables that the operator has to be aware of when he's applying this to make sure that he is doing the best possible job. Even if you get a really good operator and they put it in really well and your whole wall is airtight, you could still have this issue. 

Spray foam is prone to air leakage. I recommend you don't depend on spray foam for complete air sealing. Spray foam will get you where you're going, but if you're trying to get low, let's say passive, which is 0.6 ACH, then you've got to do a different strategy. I'm going show you what we're doing on this house for both our moisture and our air control.

So if spray foam is not the panacea of air sealing that we might have thought it was, what do we do in this case? 

We're getting our air sealing from the outside of the wall with luma. This is Polly walls Illuma flash, and it's a fully adhered WRB stuck to our OSB and seals all of the seams in between the different panels, so we don't get air infiltration through there now. Some different products applied with, say, cap head staples will do okay on infiltration because they will get sucked in tight between those when the airs are leaking in between those seams. The fabric will get pulled in tight and will stop that air leak somewhat. Still, on exfiltration, you'll create a balloon you're blowing that WRB away from your wall, so I like the fully adhered membranes for air sealing. 

Now, remember the wall coming down to the foundation is another very weak spot for air infiltration. On the inside, remember I said I didn't like the spray foam between the bottom plate and the foundation? It chips away. If that chips way, then air can leak right through that scene. What we do is we use blue barriers joint filler, and this is an adhesive as well as a filler, so it fills the gap. Still, it also sticks tenaciously to both the concrete and the bottom plate, preventing any air from coming up in there we did that before we put on the poly wall Illuma flesh. Then we illumine underneath that seam so any water that gets back here runs and can drain away on the foundation.

If you would like to know more about spray foam insulation, feel free to send us your questions. Also if you are looking for a distributor, we recommend the company ArmorThane. With over 30 years in the industry, they are the go to company when it comes to spray foam.

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