If you don't have the patience to slowly fill the void with spray foam through holes drilled in one of the studs, you could (if you were an experienced carpenter) use a Sawzall to remove one of the studs and re-frame the corner as a two-stud corner. Then you could either insulate the void with a fiberglass batt or simply present the two-stud corner to the spray-foam contractor as an accessible corner.
The drawback to spray foam insulation is it's been known to cause certain health issues such irritation of the eye and the gastrointestinal and respiratory tracts. Direct contact can cause inflammation to the skin, and some individuals have been known to break out in a rash on the arms, chest and neck area. Spray foam insulation has also been linked to a few cases of hypersensitivity pneumonitis. This condition can cause:
Yes, a new roof should be coated if the building owner wants to add a highly reflective roof coating to reduce energy costs. The buyer should be aware of any warranties provided for a new roof that may violate that warranty during the period it is in force via the use of a roof coating. This will extend the roof’s service life. A reflective roof coating will reduce the heat load on the roofing assembly.
Silicone based coatings can be spray or roller-applied, and should utilize a medium-nap roller when rolled. These coatings are applied anywhere from 2 to 3.5 gallons per 100 square feet, depending on the substrate. Silicone has two major advantages over the other four types of coatings that should be considered when searching for the best roof coating: 1) it can resist ponding water for extended periods of time and 2) it can adhere to most substrates without a primer. Because of these two major advantages, silicone is the best roof coating that satisfies both quality and cost-effectiveness.
Elastomeric coatings offer effective and affordable solutions for fixing roof leaks. The coatings can be used to repair any type of roof leak. The elastomeric roof coatings can be used throughout the year because they stretch and contract easily to adjust to winter and summer temperatures. It is usually made using polymeric products such as acrylic alongside white pigments like titanium dioxide. This helps create an opaque and reflexive final product.
Open cell is that type of foam in which the cells do not close completely. As the open-cell foam uses less number of chemicals, it is less costly. The foam acts as a barrier for, but cannot barricade water vapor. It has a sponge-like an appearance and can be used on the interiors walls of a home or building, as it causes a reduction in sound. The foam is not used for the outdoor applications.

Spray polyurethane foam, or SPF, is the main type of 2-part, closed-cell spray foam used by insulation contractors. Large-scale insulation jobs require special equipment as well as safety gear to protect the installer from chemical fumes during installation. When the foam cures and hardens just several minutes after application, it's completely safe for as long as it stays in place.

How Much Better Is Spray Foam Insulation


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]

Spray Foam Cost


Closed-cell (aka two-pound foam) is denser than open-cell at about 2 pounds per cubic foot. Its R-Value is between 6-6.5 per inch. As a result, this kind of foam is much more expensive than its counterpart. The reason closed-cell doesn't need a vapor retarder is because it already has one. It's permeance is 0.8 perm, which means it can handle cold climates without the use of an additional board or drywall. Closed-cell uses hydroflurocarbons (HFCs) as part of its makeup. However, this material has been known to have a high global warming effect. If you want a green insulation solution, this is not the material to use. A way to avoid this and still use closed-cell is by installing it alongside fiberglass batts. https://youtube.com/watch?feature=player_embedded&v=ggLAUsiuI_o
This depends on the geographic location, insulation, and cost of electricity. Lawrence Berkeley National Laboratory (LBNL), Oak Ridge National Laboratory (ORNL), National Roofing Contractors Association (NRCA), and several roofing material manufacturers have computer programs that can estimate the savings. A growing number of energy consultants are available to provide environmental regulation compliance information.
RE: my June 12 post...We went ahead and had the attic sprayed with a Soy-based product. Stayed in a hotel for 3 nites. Still smelled a little bad but that's gone away over time. I'm very glad we didn't use the other foam as even that much outgassing of a petrochemical could have sent my wife to the hospital. Unfortunately, the spray crew didn't speak English(at least not to me) and were kinda lazy, so they ended up spraying over some can fixtures from the kitchen below that were not insulation-contact rated. So I hired an electrician to come out, pull down the cans, pull out what he thought was an appropriate amount of foam to create a big enough air space and then re-install the cans. I billed the firm for the electrician plus an extra night we had to stay in the hotel and they paid, no questions asked. Guess they knew they had screwed up.  
Thank you, Allison. We have a split system unit (actually 5) with the heat being propane. The foam guy said that it needed ventilation, so completely sealing the attic wouldn't be a good idea. It sounds like you are saying that the systems need to be vented out of the attic or replaced with some type of closed system. But I shouldn't bother spraying if the plan is to leave the soffet vents open. Is that correct?

Note: The practice of foam insulating the attic has raised eyebrows in the building industry because "standard" roofing techniques call for the attic to be ventilated; however, in a vented attic situation it will become approximately 130 degrees in the summer. There's no reason for an air-conditioning and vent-ductwork to have to work in that type of severe conditions. By applying Icynene right on the underside of the roof deck, the severe temperatures no longer exist in the attic. In short, the attic is now a "conditioned" space of the house that is just as comfortable as any other room in the home. This is called a "Compact Roof", which means you can frame right up against it. The one drawback of using expanded foam on the inside of the roof is that this will cause the temperature of the shingles to rise, but how much is not yet known. And how much damage a rise in temperatures could cause is debatable.

Roof Spray Foam Insulation

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