There are many things to look for in contractors in general: a safety program in place for workers and customers, licensed and insured, and good quality references. When it comes to spray foam there are a few qualities special to the industry that you must look out for. There are many fly by night spray foam contractors that come and go. They have very little training and even less experience which always ends badly in this industry.
This all applies to CCMC approved 2lb polyurethane spray foam.
1: Spray foam installation is to a extent dependent on atmospheric conditions and if not monitored can create insulation that is not the best. If your contractor shows up on a day that is pouring rain, you should probably ask if it’s OK to spray. If he says that everything is fine and does nothing to control the spray area, find a new contractor because he doesn’t know polyurethane application well enough yet. Moisture and humidity are sworn enemies of spray foam application, for the fact that one part of the mixture of polyurethane spray foam reacts with any amount of moisture no matter how small and anything over eighty percent humidity is questionable.
2: Take a peek at his trailer and see if it is organized with nice and fairly new equipment, within the last ten years. This is important because the old pumps can spray off ratio with no shut down, creating either a resin rich or isocyanate rich foam. This is in my opinion is one of the leading causes of foam that smells after install.
3: Polyurethane spray foam has to be installed in layers with no more rise than two inches at a time. This is due to the fact that when the two components of 2lb spray foam mix they create heat, if too much is applied the foam can cook itself and cause cracks and lingering odors. Asking how many passes it will take to get an r20 rating on closed cell 2lb foam should get the answer of min 2 passes for any 2lb foam on the market. If they say one pass will do it they are not totally trust worthy; the best 2lb foams rate at r6 per inch which means you need at least 3.5 inches to get a r20 rating.
These are, in my mind, the most important things in this industry to watch for because they are the biggest factors to getting a quality install. Any contractor that sprays foam should have a certified sprayer on the job. Ask for a ticket or documentation before the job starts.
We want everyone to get a quality product because bad installs hurt our industry, product reputation and you the customer.