Spray foam insulation, when properly installed is both an air barrier and when closed cell foam is used at the proper depth a vapor barrier!  Before hiring any contractor you should establish the brand of foam being used and verify that with the named manufacture.  Please ask for ESR reports and MSDS sheets on any foam being installed in your home. A couple areas where you might consider spray foam insulation include:
Hydraulic or air powered airless provide a more uniform pressure control since the paint piston moves at a constant speed except when it changes direction. In most direct drive piston pumps, the piston is crankshaft driven in which the piston will be constantly changing speed. The linear motors of hydraulic or compressed air drive pumps, are more efficient in converting engine power to material power, than crankshaft driven units. All types of paint can be painted by using airless method.
4 years ago I applied Gaco Roof, coats to an Office Building flat roof and have zero leaks since that time. This saved me $30,000 compared to having a new roof installed. The roof itself was only 7 years old when I applied Gaco Roof. but due to ponding water and harsh Florida heat and UV, the roof already looked shot and was leaking. I have now used Gaco Roof on 4 flat roofs to great results. I also tried big hardware store lower cost substitutes on 2 flat roofs. Those product utterly failed 1 to 2 years. Yes, I pressure washed my roofs clean before using Gaco Roof and followed their simple installation instructions. Excellent product.
Since our founding in 1973, Dal-Bac Manufacturing Co., Inc. has grown and expanded to become one of the premier providers of coating services to customers in a diverse range of industries. We are capable of applying both solvent and water-borne coatings to a wide variety of substrates, including fabrics, films, foams, and papers. Our capabilities include both knife-over-roll and Meyer rod coating methods for roll goods up to 61” in width. With our custom built equipment, we process materials accurately and cost-effectively. Coating Services

Spray foam is available in two different types: open-cell spray foam which is usually $0.44 to $0.65 per board foot and closed-cell spray foam which is about $1 to $1.50 per board foot. The average cost to have spray foam professionally installed is about $2,347. This number can vary depending on whether the home being insulated is newly constructed. However, finished homes are not a good candidate for spray foam insulation but great for weatherization or an energy audit.  

During the 1980s, a class of thermal spray processes called high velocity oxy-fuel spraying was developed. A mixture of gaseous or liquid fuel and oxygen is fed into a combustion chamber, where they are ignited and combusted continuously. The resultant hot gas at a pressure close to 1 MPa emanates through a converging–diverging nozzle and travels through a straight section. The fuels can be gases (hydrogen, methane, propane, propylene, acetylene, natural gas, etc.) or liquids (kerosene, etc.). The jet velocity at the exit of the barrel (>1000 m/s) exceeds the speed of sound. A powder feed stock is injected into the gas stream, which accelerates the powder up to 800 m/s. The stream of hot gas and powder is directed towards the surface to be coated. The powder partially melts in the stream, and deposits upon the substrate. The resulting coating has low porosity and high bond strength.[1] Spray Coating