Today’s “third generation” of blowing agents have a GWP of 700 to 1000 which is still remarkably high considering water/CO2 has a GWP of 1. However, innovation from some chemical manufacturers like the Chemours Company have introduced the next generation of HFO blowing agents such as Opteon 1100, which significantly reduces the GWP impact when using closed-cell spray foam insulation products.

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 the case you have above the installer wasn't reading his foam. They must be trained to do that as they spray. Temps and conditions are constantly changing thru out the day. Either he wasn't properly trained or if he was,he wasn't doing his job! This is a serious problem with people jumping in to the foam business. A lot of homeowners and builders are looking the best price and end up with someone who doesn't know what they are doing. Hope this info helps. Foam insulation is a great product. It just has to be done right by someone who knows what they are doing.
While coatings may potentially stop minor leaks, the roof should be properly repaired and dried prior to coating application. Coatings may be able to seal pinhole leaks, which are leaks not visible to the naked eye. If the roof is leaking, the roof leak will need to be identified and repaired prior to any recoating; do not expect the coating to find and seal the leaks.
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.
c) Make sure that the over expanded access is properly removed from the walls. We had a junior cutter taking too much off by bending his saw into the cavity. Look closely at the inside wall corners, and ceiling/wall corners to make sure that the foam is properly removed flush with the studs. If it has not been cut back flush it may lead to uneven drywall finishes .
Builders often turn to high-density SPF when high insulation values and strength are needed. As its name implies, this foam has a denser structure than either of the other SPF types. Therefore, it does not expand as much as lower density foams and requires more material to cover and insulate any given space. This spray foam is often an excellent choice for roofing or other exterior insulation because of its seamless, monolithic nature. High-density SPF can also help reduce energy costs significantly over a roof’s lifetime due to its thermal resistance properties. It also offers increased protection against air and water infiltration and strengthens the structure to which it is applied. The bond that SPF forms to the roof can increase a building’s resistance to wind uplift, which can help reduce damage experienced during periods of high wind.
Allison--would be very interested in your take on the GHG issues of foams, which have received lots of smart commentary recently. To highlight a few: architect Jesse Thompson's comments on Tom's Good vs Bad post on Energy Circle, the very thorough piece by Alex Wilson on Green Building Advisor and Michael Anschel's cautionary diatribe on Remodeling. 

How Much Does Spray Foam Insulation Cost

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.
Spray foam insulation is typically priced by volume, meaning your cost will depend on how much material you need to use to insulate your space, although other factors may influence price as well. In most cases, the cost of spray foam insulation is more than worth it, as it's a once and done upgrade that will not only provide energy savings in your home, but also improve your home's overall comfort.
Good article, but it seems like you can chalk up almost all of those problems to the experience level of whomever is spraying the foam. Spray foam isn't an inherently bad product, but it's pretty easy to botch if the hired company is inexperienced. Fiberglass may be foolproof to install, but then again it has a terrible R-Value compared to a good spray foam. People just need to get referrals and do their homework whenever they research a spray foam contractor.
Fill and seal expanding foam sealant is urethane Fill and seal expanding foam sealant is urethane foam designed to fill large areas quickly and permanently. Uses include filling holes cracks or gaps that require a complete airtight and waterproof seal but are too large to be filled with ordinary caulk. The foam expands approximately 3 times its original ...  More + Product Details Close
This coating is also efficient with a coverage area reaching between 42 and 46 feet. And regardless of the weather, you can apply and use it in your roof to achieve the protection for it you need. Just as what you can read in RV rubber roof coating reviews, this product can work in all temperatures. Regardless it is hot or cold outside, you can easily apply and ensure of its adhesion on your recreational vehicle roof.
Water-based acrylic coatings have more than 30 years of proven performance over a wide range of substrates. It is the coating of choice for metal roofs since it is highly reflective, can be easily tinted and is not extremely slippery when damp. When used with our rust primer, even rusted roofs can be saved. TIP: If you have a metal roof or a low slope roof that doesn't pond water, consider acrylic coatings.
Spray foam is a chemical product created by two materials, isocyanate and polyol resin, which react when mixed with each other and expand up to 30-60 times its liquid volume after it is sprayed in place. This expansion makes it useful as a specialty packing material which forms to the shape of the product being packaged and produces a high thermal insulating value with virtually no air infiltration.

R-value is the term given to thermal resistance to heat flow. The higher the R-value of an insulation product, the more effective the insulation properties. Spray polyurethane foam comes in a range of densities and cel structure. Low density foams are referred to as Open Cel SPF while higher density foams are referred to as Closed Cel foam. 1.8-2 pound polyurethane foam has the highest R-value of readily available spray foam insulation used in homes and buildings.[4]

Roof Spray Foam Insulation