Barrier insulation is insulation that is placed under concrete foundations or under a slab that is used to protect the home or building. In most cases, insulation is meant to help prevent heat loss or heat intrusion, depending on the season. That is a common use for barrier insulation as well. However, it can also serve a secondary purpose as a moisture barrier.
As with any type of insulation, barrier insulation must protect from outside elements in order to make the home as efficient as possible. Traditionally, the underside of a home or building has not been insulated against the elements. However, as more emphasis is placed on total home efficiency, the underside has become more of an area of concern.
The reason why under-slab insulation may be so important is due to the ground temperature in many parts of the world. For example, in the United States, ground temperatures average, throughout the entire year, approximately 55 degrees Fahrenheit (11 Celsius). Even in warmer climates, there may be times when the soil cools enough to create sufficient heat loss during certain times of the year.
Insulating under a foundation, while not the highest priority of areas to insulate in a home, can be a wise choice. Nearly a third of all air leaks in a home are through the flooring, walls and ceiling. Thus, barrier insulation can be an effective part of an overall home insulation strategy, but should, by no means, be considered the only part of a home protection strategy.
While it may be possible to use barrier insulation in an existing home, the most practical time to apply it is during new construction. This way, the barrier insulation can be laid before the foundation is completed. In homes with a raised foundation, it may be considerably easier to install barrier insulation. Of course, that depends on how accessible the underside of the home is through the crawl space.
Barrier insulation is made using a couple of different materials. The core of the insulation is polystyrene. The outer area consists of a thin, laminated film of polyethylene making up the remainder of the material. It is usually applied in rolls, much like some forms of attic insulation.
Given its material composition, barrier insulation also provides an effective barrier for moisture. This can help, especially in homes with wood flooring, which may become warped with moisture over time. While this may not increase the home's efficiency significantly, it can help reduce or delay costly maintenance projects.