Urethane insulation is a building product used to prevent air transfer through the exterior walls of a home. It is comprised of polymer chains connected by organic compounds known as carbonates, or urethanes. The terms urethane and polyurethane are used interchangeably when it comes to most applications, including insulation.
There are two basic types of urethane insulation, including rigid foam boards and spray foam. Rigid boards come in a variety of sizes, and typically range from 1 to 2 inches (2.54 to 5.08 cm) in thickness. These boards are primarily used in new construction, and are installed inside of walls or around other structures in the home. Spray foam insulation is typically used in existing structures, which may lack sufficient insulation material. This product is sprayed into the wall through tiny holes, and quickly expands to fill the entire wall cavity.
This material can be used is a number of different application in the home. Rigid insulation is frequently installed on the exterior of the wall framing system, where it is sandwiched between the home's sheathing and exterior cladding layers. Sheets of rigid insulation may also be attached to the home's roof or foundation, to provide additional thermal resistance in these areas. Spray foam is installed inside the same cavity as the wall studs, with sheathing, plywood, or drywall used to form the wall's boundaries.
Urethane insulation offers several advantages over other insulating materials. Though it is slightly more expensive than traditional fiberglass batts, it is considered a superior insulator, with two to three times the thermal resistance of alternative products. The closed-cell construction of urethane foam helps to block air flow, and also keeps the material from collapsing or sagging. Sheets of the insulation take up very little space, resulting in thinner walls and more available living area. Finally, urethane insulation is difficult to ignite, and is more resistant to fire than either fiberglass or polystyrene insulation.
Despite its many benefits, there are a number of factors that must be considered when using urethane insulation. As it ages, this material experiences a condition known as thermal drift, which can lead to decreased levels of thermal resistance. Adding a foil or plastic coating to the insulation can eliminate or slow thermal drift. Urethane insulation is also susceptible to insects burrowing into the material, which reduces its effectiveness. To prevent insect damage, insulation should be treated with an insecticide, especially when installed on foundation or basement walls.