Spray foam insulation is a close relative of foam board insulation, in the sense that the material is very similar, as there are also foam core boards made from the same foam spray foam is made of and the idea behind it is closely related with foam board insulation, working in a similar style. In a way, expanding foam is the spray version of it’s relative, each with its advantages. Unlike rigid foam board insulation with foam core boards, expanding foam is sprayed out of a gun, over the areas that must be insulated, therefore, making it’s way over every shape of the area, and getting in any cracks or spaces, even some of those that might be hard to access or even not visible.
Expanding spray foam insulation is made out of a material very similar to polyurethane. Polyurethane is the foam that is commonly used to seal the spaces around windows and doors, usually sprayed from a can. Its advantage is that it takes very little material to seal the said areas, as the foam expands after applying, taking a rigid shape of the area it was sprayed in.
Working on a similar principle, is easier to apply than foam board insulation, because it does not require special fittings, as it sticks to the surface it is applied over, and since it does not consists of foam core boards, it doesn’t need special seals like foam board insulation does in order to prevent unwanted draught.
One of the disadvantages of using this kind of insulation is that it must be applied using special tools. If you are interested in using this type of insulation on a small scale only, it might not be advantageous to buy the corresponding equipment, being more viable to rent the equipment or get a trained team to do it for you. However, since normal foam core board would also require a professional installation this disadvantage is somewhat mitigated.
If you intent on insulating a barn, a garage or even your entire house you should certainly consider spray foam insulation as one of the options.