The first step in any successful project is making sure you know what you are setting out to accomplish. For attics, either the floor or the underside of the roof can be sprayed. If you want to temperature control your attic, convert it to living space, or store items in it that are temperature sensitive, then spraying the underside of the roof is the way to go. If you are simply trying to better insulate the living area below the attic floor, then it makes sense to put your airtight “lid” closer to it, so you aren’t paying to heat or cool all of that unused attic volume.


Your total required number of spray foam kits is determined by your total board feet need. A board-foot is one squared foot at one inch thick. If you are spraying the underside of the roof, our standard recommendation is a thickness of 3”. So, total up the surface area of the roof decking you will be spraying, and multiply it by 3 to get your total board feet. If you are spraying the floor, you can create an airtight seal with just 1” of foam and then use something less expensive to add cheap R value, like batts or blown-in insulation. Measure the squared feet of the floor, and that number will be your total board feet need at 1”. Take your total board-feet need of either your floor or roof, and then add about 10% or so for waste. Divide your total board-feet need by 600 (the board-feet a Foam it Green 602 kit can cover), round it up to the next whole kit, and place your order!


It’s difficult if not impossible to get foam off of surfaces it hits. So, be sure to take the time to cover anything you do not want foam stuck to including floors, windows, equipment in the area, and even you once you start spraying! Along with the recommended PPE, the sprayer should have no exposed skin or hair during application. How do you get foam out of a beard? In a word, scissors. It’s recommended to use sheets of plywood to stand on if you do not have a traditional floor in your attic. Trying to tip-toe along the edges of the joists is dangerous, and we don’t want you, or your heavy spray foam kit, falling through the ceiling below. As always, make sure your target spray surfaces measure between 65F-85F.


Target a wet foam application thickness of 1/3” as that will expand to one inch cured. When spraying overhead, it’s recommended to leave off the fan spray tip and simply use the mixing nozzle alone. Get your hand a bit closer when pointing up, and use a lighter trigger pull so you don’t “bounce” the foam off the surface.


For under roof spraying, you have more waste when spraying overhead because the foam is fighting gravity. So again, don’t use the green fan spray tips and do use a lighter touch on the trigger so that the foam does not bounce off the surface. Also, you can spray the foam directly to rafter channel vents, or “baffles”, if preferred. We recommend building in a bit more waste than normal when spraying overhead.

Don’t spray directly into the soffit vents. Instead, block them off with a material like foam board first. Since you are using closed cell, the foam does not need the attic ventilation that usually exists for less dense materials to evaporate out moisture it collects.

When spraying the floor of the attic, however, keep your soffit vents open and free of foam or other forms of insulation. Since you are putting additional insulation over the top of the foam, the batts or blown-in materials will need that airflow even though you are getting that great, airtight seal at the floor.

Our Recommendation

Standard Closed Cell Spray Foam!

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