Spray foam is fabricated from a variety of materials, including polyurethane, polyisocyanurate and phenolic foam. They are manufactured in a liquid form and combined with a foaming agent. The foam is then sprayed into an area using a pressurized air blower. The foam hardens and expands on contact with the space to be insulated, conforming to its contours. This makes sprayed foam a very effective thermal barrier, as it minimizes air voids, and useful for insulating hard-to-reach areas.
Foam board insulation is commonly manufactured from polystyrene, although polyisocyanurate and polyurethane are also used. The material is combined with a gas before being compressed into boards. They can provide structural support to the building as well as insulation.
Foam insulation, whether it is sprayed or in a rigid board, is an inert material. This means that it does not move and change shape or composition, as other forms of insulation, such as cellulose, can do. As a synthetic polymer, it is not prone to natural decay. As such, foam insulation will last for the lifetime of the building in which it is installed.
Foam insulation will only last for such a long period if it is not damaged. All foam insulation must be covered by a fire-resistant barrier. Gypsum wallboard or drywall are commonly-used materials for barriers. This will also prevent any damage from direct sunlight if the foam is installed in a room with windows. In areas that are prone to condensation, a vapor barrier should be installed over the foam to prevent mold and mildew forming. Vapor barriers can be made from foil, paper and plastic. They also prevent insects burrowing into the foam, which would compromise the insulation's effectiveness by allowing air to penetrate it.