Foam board insulation is a highly effective form of insulation that is used in buildings where space is limited. It is better able to regulate air flow and temperature changes than fiberglass and other forms of insulation, but as a result, foam board insulation tends to be quite a bit more expensive than these alternative materials.
Foam Board Insulation Overview
Polyisocyanurate and polyurethane are two materials that are commonly used to create foam board insulation. Unlike other types of urethane boards, these boards contain a gas that has a low conductivity level within closed cells on the board. As a result, the boards have a very high R-value, typically around R-7 or so per inch of board.
Additionally, both of these materials are occasionally set up as a liquid or spray form of insulation, although the preformed and board style is more common. Polyisocyanurate and polyurethane are both relatively flexible and moldable materials, and it is also possible to come across foam board insulation made from these chemicals as laminated panels.
Loss of Effectiveness
One concern regarding foam board insulation of this kind is that the gas will gradually escape from within the cells of the insulation. The result is that the R-level of the insulation will drop slightly over the years and months after the insulation is installed.