I am an Architect in Toronto. I am designing a new roof addition to a row house building. Because of existing conditions and the shape of the new roof. It may be easiest to use closed cell spray foam within the areas of the joists. My question is when spray foam is used in this situation do I need to worry about how the joist members may be thermal bridges? It is not common to provide a little bit of rigid insulation to protect the joist members? The additional layer of outboard insulation will require an extra layer of plywood above the insulation which will add to cost.
OK, Peter, I finally went back and read Alex Wilson's article on what he perceives as a serious problem. I haven't seen the full report, but based on the summary he wrote on the Green Building Advisor website, I question the science. It seems to me that he's chosen the wrong metric and he's basing his conclusion on too many assumptions because he doesn't have enough data. You can see my comments at the end of his article.

They’re the more expensive option than the first one we have discussed above, but they also offer top benefits for the RV owners who want to repair or maintain their RV roof and protect it from UV rays and harsh weather elements. Based on many reviews, these types can offer more durability than the silicone and acrylic types. They can also offer an excellent impact resistance from twigs, leaves and other outer elements.
During colder months, 2 component foam is very sensitive to temperature variances. Per product instructions, both tank temperatures need to be above 70°F (21°C) for at least 24 hours prior to use. All application surfaces should be clean/dry and above 60°F (16°C) prior to application. Variance outside of the recommended temperature can affect foam yield and performance. https://youtube.com/v/ggLAUsiuI_o?version=3

After researching this, Im curious about a method called poor mans sprayfoam where foamboard is cut to size between studs and sprayfoamed around the perimeter. Aside from the labour doing the job yourself, the cost seems comparable, is one better than the other? What about the quality of the canned sprayfoam around the perimeter? When i see sprayfoam done, it is never a full depth of the studs, so you would get 2.5-3 inches in a 3.5" (2x4) wall. Any thoughts? 
Spray polyurethane foam (SPF) is a spray-applied plastic that is widely used to insulate buildings and seal cracks and gaps, making the building more energy-efficient and comfortable. SPF insulation is known to resist heat transfer extremely well, and it offers a highly effective solution in reducing unwanted air infiltration through cracks, seams, and joints. https://www.youtube.com/watch?v=ggLAUsiuI_o&app=m

The product is an acrylic coating, which is packed conveniently for ease of use. As it is also in one-gallon size, you can rely on its supreme area coverage reaching up to 125 square feet. The Dicor rubber roof coating is also very easy to apply. When shopping around for a roof coating, we believe it pays off to find an easy to apply product for fast results. It is one of the best qualities of the RV roof coating that makes it a top pick in the category.


Polyurethane is a closed-cell foam insulation material that initially contains a low-conductivity gas in its cells.[5] As a result of the high thermal resistance of the gas, spray polyurethane insulation typically has an initial R-value around R-3.4 to R-6.7 per inch.[5] In comparison, blown fiberglass typically has an R-Value of only R-3 to R-4 per inch.[6] http://www.youtube.com/watch?v=ggLAUsiuI_o
Polyurethane is a closed-cell foam insulation material that initially contains a low-conductivity gas in its cells.[5] As a result of the high thermal resistance of the gas, spray polyurethane insulation typically has an initial R-value around R-3.4 to R-6.7 per inch.[5] In comparison, blown fiberglass typically has an R-Value of only R-3 to R-4 per inch.[6]
R-value is the term given to thermal resistance to heat flow. The higher the R-value of an insulation product, the more effective the insulation properties. Spray polyurethane foam comes in a range of densities and cel structure. Low density foams are referred to as Open Cel SPF while higher density foams are referred to as Closed Cel foam. 1.8-2 pound polyurethane foam has the highest R-value of readily available spray foam insulation used in homes and buildings.[4]
Sean, thanks for jumping in and answering John's questions. About choosing the right foam, I intentionally avoided the open cell vs. closed cell foam debate. I did this partly because it's worthy of an article all by itself, but mainly I didn't include it because, despite all the warnings the two sides issue about the other, I've never personally seen a problem caused by using open cell where they should've used closed cell or vice versa. I'm sure things like that happen; I just haven't seen it yet. 

As this example illustrates, it's important to seal the envelope completely. One of spray foam's biggest selling points is its air-sealing ability, but it can't seal places where it's not sprayed. One of the nice things about using spray foam in new construction is that you can do a Blower Door test before the drywall goes in. Even better, you can test for leaks with a fog machine. https://youtube.com/v/ggLAUsiuI_o
While coatings may potentially stop minor leaks, the roof should be properly repaired and dried prior to coating application. Coatings may be able to seal pinhole leaks, which are leaks not visible to the naked eye. If the roof is leaking, the roof leak will need to be identified and repaired prior to any recoating; do not expect the coating to find and seal the leaks.

While the R value will vary, most ocSPF products have an R value of around 3.8 per inch. Unlike medium-density closed-cell SPF, ocSPF is not a vapour barrier. When installed at 5.5 inches or more, ocSPF does act as an air barrier. It is often used for interior walls because it provides sound reduction by blocking and absorbing air leakage. It is usually only recommended for indoor applications.


To see if ShippingPass is right for you, try a 30-day free trial. Also, with ShippingPass, there is no need to worry about commitment. If you decide you want to discontinue the service, you can cancel your subscription at any time. No matter what your shipping needs, Walmart's got you covered. Sign up for ShippingPass so you can shop more, save money and live better.
Check with the coating manufacturer who may be able to suggest applicators who have used their products and have familiarity with the application. Another option would be to interview contractors and ask specific questions about their proven ability to install roof coatings. Contractors affiliated with the National Roofing Contractors Association (NRCA) or local roofing contractor trade associations typically are more knowledgeable. Consult those groups’ websites for contractors.

How Much Does Spray Foam


RetroFoam of Michigan has more than 15 years of experience insulating thousands of homes and pole barns across the lower peninsula. We hear a lot of misconceptions about foam insulation and work to make sure we clear up any wrong ideas about foam insulation. Our staff helped us put together this list of misconceptions adding their insights to dispel any misinformation. 

Roof Coating Colorado

×