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.

I had a hole in the drywall in our bathroom that was about 2 in x 5 in that I used Great Stuff to fix. I am impressed with the characteristics of the filler. It filled the hole completely in a few seconds of application. I will warn anyone using it though to make sure you don't fill the hole entirely flush to the wall because this stuff continues expanding after you apply it. I didn't think about that but no big deal really because you can sand it which is exactly what I did, and then applied spacial and paint and it is almost as good as new. For the price this was a heck of a deal because I only used a tiny amount and now am left with nearly a full can. I guess I will have to find somewhere else to use it now. Great product, ... full review

Spray foam insulation is a great product. Homes insulated with it can be some of the most efficient and comfortable homes built. I've been in plenty of these homes and can tell you that when spray foam is installed properly, they outperform 99% of fiberglass batt-insulated, stick-built homes. (I can also tell you that 73% of all statistics are made up on the spot, so please don't ask for documentation of that statistic.)
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.

Spray polyurethan foam does effectly prevent all six of these heat transfer methods from occurring. These should be the mechanisms by which you judge insulation, in addition to their R-Value. If you're uncertain about installing spray foam insulation, Energy Star has a map that recommends levels of insulation by R-value and cost-effectiveness in the United States. 

Roof coatings can add 25 years to the service life of a roof and reduce the amount of discarded roofing materials that end up in landfills. The infrared image on the right shows 175 °F (79 °C) on the uncoated (black) section of the modified bitumen roof. The coated (white) section is 79 °F (26 °C). Field studies have shown that cool roof coatings can lower rooftop temperatures and reduce air conditioning bills.
The average price to cover 200 square feet with a foam insulation kit will run between $300 and $600 (about two to three kits). Inside these kits is something called Icynene, a foam made from two liquids that are heated and pushed through a gun on the can. When Icynene is released, it expands up to 100 times its size as it hits the surface area you're covering. These can contain a lot of gasses, making its installation a dangerous process. Even low-pressure sprayers can be harmful to homeowners' health.

How Much Is Spray Foam Insulation

Typical roof coating dry film thickness vary from paint film thickness (plus or minus 3 dry mils) to more than 40 dry mils. This means a roof coating actually becomes the top layer of a composite roof membrane and underlying system. As such, the roof coating is the topmost layer of protection for the membrane, receiving the impact of sunlight (both infrared and ultraviolet (UV), rain, hail and physical damage.
For example, a hybrid solution of spray foam and fiberglass batts or rolls combines the air-sealing and vapor-retarder benefits of foam with the economical thermal performance of fiberglass. Another option might be to install spray foam in places that are hard to reach or seal, such as rim joists, the attic floor, and eaves, and then install fiberglass batts and loose-fill in the in the open areas, greatly reducing any draftiness while helping the project budget. Incorporating spray foam into hybrid solutions enhances the building envelope and seals efficiently at a reasonable cost. 
Installing spray foam is easy to do and can dramatically improve a building or home’s energy efficiency and thermal resistance. Our closed cell foam is so efficient just 3 inches of foam appled inside of wall cavities provides an insulation value of over R18!. Our products are specially formulated for both new construction and existing homes and buildings.
A. You can use closed-cell spray foam that way if you want, although you should realize that the spray foam will prevent the roof sheathing from drying inward. This approach should only be used if the roof sheathing is bone dry, because it will never dry when sandwiched in this manner. Most building scientists would prefer to see fiberglass rather than closed-cell spray foam under the roof sheathing in this type of assembly.

Roof Coating Seal