Foam is very sticky; you'll need to wear disposable coveralls with a hood, and gloves, a face mask, and eye protection. It takes some practice to spray foam evenly and, because it expands so dramatically, to control its depth; 2 inches is all you need to seal the joist cavities. You need a clear area so that you can work without interruption; any pause longer than 30 seconds will clog the nozzle and require putting on a new one. It's also critical that the air temperature stays between 75 and 85 degrees.
Most closed-cell spray foam is now formed using hydrofluorocarbon (HFC) blowing agents that have high global warming potential, partially or completely offsetting the climate benefits of the energy savings they can offer. In the United States, HFCs are scheduled to be phased out by January, 2021. A few spray foam suppliers have started supplying spray foam blown with hydrofluoroolefin (HFO) blowing agents without this problem as of early 2017.[14]

a) Make sure that your house has been well heated prior to installation because the foam expands at different rates as it hits surfaces with different temperatures. If it is cold outside the sheathing may be much colder than the studs consequently the foam may expand more from the sides of the wall cavity creating air pockets in the wall cavity. This can be minimized by an experienced installer.
Open-cell is also known as half-pound foam. It has an R-Value of 3.5-3.6 per inch, and its density is bout 0.5 pounds per cubic food. Low-density foams like these are made partially from raw biological materials Carbon dioxide or water is also used in the makeup. Open-cell uses far less material than closed-cell, but its R-Value is lower. Also, open cell requires a vapor retarder (like gypsum wallboard) and is riskier when used for roof sheathing. It's not highly recommended that you use open-cell insulation if you live in a cold climate unless you have that extra barrier. You should also compare how much money you spend versus how effective the open-cell insulation is wherever it's installed. 

If you haven’t considered spray foam insulation, now may be the time to start looking into it. As you know, having proper insulation will help reduce your heat and air conditioning bills. In specific, spray foam insulation can be particularly helpful during renovations. It can provide a barrier between outside walls, and even a sound barrier for the inside.
Another thing we love about the Liquid Roof is its ability of not being damaged by freezing and other extreme temperatures. You will also appreciate its ability of staying flexible for a longer period of time. Did you know that it could also contract and expand as you roof moves? That is one of the things to look for when shopping around for this kind of product we found in the Liquid Roof. http://www.youtube.com/watch?v=ggLAUsiuI_o&app=desktop
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.

The United States has adapted to using sprayfoam insulation and a new technology called Wall Injection to retrofit existing wall construction by drilling small holes between wall studs in the structures framing and filling the void with a less aggressive expanding water based foam. This allows existing home and business owners to conserve energy by creating a thermal envelope in their existing structure. 

Roof Coating Seal

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