Radiant Barriers and Reflective Foil Insulation – Where to Use?

As energy costs continue to climb and we more faithfully commit to demand less energy, the use of alternative insulation products continue to grow.

For years, fiberglass was the most widely used form of insulation. Fiberglass insulation is excellent at slowing the transfer of convective heat. Its performance is measured in an r-value number. Generally the thicker the insulation is, the greater the r-value. Fiberglass insulation is relatively inexpensive, installs quickly, and is readily available.

Although fiberglass is ideal in many applications, it does have drawbacks. It is prone to insect and rodent infiltration. Fiberglass also cannot handle excessive moisture. The r-value of fiberglass insulation drops sharply when any level of moisture is added to the material. This eliminates its use in crawlspace applications and many areas around concrete slabs. This also limits its ability in attic applications.

In the limitations of fiberglass is where radiant barriers and reflective foil insulation products excel. Radiant barriers and reflective foil insulation are impervious to moisture, and insect and rodent infiltration. They are designed to be used in the following applications:

House-wraps: Radiant barriers replace existing house-wraps. Standard house-wraps are a strong weave of perforated vapor barrier. Radiant barrier house-wraps offer this same characteristic but also with a reflective layer allowing it to also block the transfer of radiant heat.

Attics: Radiant Barriers also excel in attic applications. In attics, moisture levels constantly change and most of a home’s heat is either lost or gained here. Fiberglass insulation is not enough to stop the transfer of radiant heat. The use of a radiant barrier that reflects radiant heat is now imperative in attics.

Under-Slabs and Basements: Basements are infinite heat sinks due to their contact with the earth. Their high moisture level severely limits the use of fiberglass insulation. Reflective foil insulation is not affected by moisture and its radiant heat blocking properties are also ideal in these applications.

Crawlspaces and Duct-Wraps: In these areas reflective foil insulation is the only product to use. Fiberglass insulation is not appropriate. Its inability to handle moisture and insect and rodent infestation make its use impractical.

To prevent any confusion, radiant barrier and reflective foil insulation products are designed to stop the transfer of radiant heat. Fiberglass insulation is designed to stop the transfer of convective heat. It is unfair to judge the two types of insulation against each other. They are designed to stop two different types of heat transfer. Stopping both convective and radiant heat transfer has to be done in order to have an efficient insulation system. To do this, radiant barrier reflective foil insulation technology and fiberglass insulation, or another product designed to stop convective heat gain should be used together whenever possible.