Due to its relatively large cell structure, low-density foam stays somewhat soft and flexible after curing. This increases the likelihood of its continuing to provide high insulation value even as the building settles and shifts over time. Low-density SPF provides heat insulation and seals airflow through cracks, joints and seams by filling the cavities. In addition, this foam can help absorb sound thanks to its soft texture and open-cell structure.
Although spray foam insulation has been in use since the 1940s, primarily for aircraft, for the past 30 years, continual product innovation has seen the increased adoption of spray foam insulation in residential and commercial construction. The rapid growth of sprayed foam insulation in building construction, thanks in part to its immediate and long-term benefits, has allowed the insulation material to sit confidently alongside traditional insulation types in providing thermal comfort for building occupants. https://m.youtube.com/v/ggLAUsiuI_o
Determining which type of SPF is right for the project involves evaluating the application area, overall budget, and scope of a project. Review insulation needs in attics, walls, ceilings, and other areas, and account for factors like project location, climate and how the building will be used. For example, an indoor swimming pool will drive towards a different SPF selection than an office building. 

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]

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

Here's a simpler, less expensive alternative: Cut some 2-inch-thick rigid-foam insulation and glue it to the subfloor between the joists or support it with nails driven partway into the joists. Then fill any gaps between the edges of the foam boards and the joists using the canned spray foam sold at home centers or hardware stores. An even easier option is to nail the foam panels against the bottom edge of the joists and seal the joints with canned foam, but you'll lose some headroom and access to any pipes and wires between the joists. As with spray-foam kits, protect yourself and the floor from the dripping globs of canned foam. A full face shield, gloves, and a hat would be a good start.

The guys who sprayed my attic were trained and certified, but I later found out, too late, that they had no experience and my attic was the first they'd ever sprayed. I was also never told to vacate my house for any length of time, and so I (and my pets) were in the house the day they sprayed and the entire time the off ratio foam was filling my home with horrendous vapors. The company kept telling me that it was a good job and I had nothing to worry about, even after I'd had 2 other experienced sprayers from 2 different companies visually examine the foam and confirm that large areas appeared to be off ratio. The 3rd sprayer from yet another company, was also outraged because the company who did my attic had failed to vacuum up all of the old cellulose insulation, and he also noticed areas where the foam was shrinking or pulling away, and this was not even 5 weeks after the spraying.  
Spray foam insulation helps lower utility costs because it blocks heat and cold from the outdoors. Recent studies by the U.S. Department of Energy state that around 40 percent of all energy is lost through poor insulation. Spray foam insulation is able to insulate homes at least 50 percent more than traditional insulation products. Spray foam insulation can also provide protection against moisture, which otherwise leads to the unwanted development of mold and mildew. And it can also be used for noise reduction as well. In fact, spray foam is good for homes and buildings in which outdoor noise can be a distraction.
Medium-density foam is applied as low or high-pressure two-component polyurethane spray foam. Medium-density foam offers specific benefits depending on the climate and the type of building in which it is used. Like low-density foam, medium-density SPF is often used for continuous insulation, interior wall cavity fill, and unvented attic applications. However, medium-density is a closed-cell spray foam; it is often used where there is need for the greatest R-value insulation per inch possible. Medium-density foam acts as an air, vapor, and water barrier, and can even help reduce noise.
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.
In addition, it's difficult for an inexperienced installer to evenly spread the insulation foam over a surface. Miissing spots can leave holes and gaps for cold air to get through. Proceed with this project yourself only if you're doing a small insulation project -- such as installing foam in a crawl space or around your plumbing. Leave larger projects like the attic, basement or garage to the professional insulation contractors. Insulation professionals have the tools, equipment and background knowledge necessary. Moreover, they know how to accurately price insulation, whereas you could inaccurately budget for a DIY project and end up paying significantly more. Don't take the medical, physical or financial risks that come with pursuing this as a DIY project unless you're absolutely certain you have the skills.

How Much To Charge For Spray Foam Insulation

One of the best ways to achieve it is to use the Heng’s rubber coating that can protect it from the elements, including sleet, wind, rain, and snow and UV rays. The product also does well in keeping our roof protected from dirt, leaves and twigs. With such protection received, our roof won’t degrade and we prevent ruining our recreational vehicle investment.

Spray Foam Roof Insulation