Why Radiant Barriers Need An Air Space

After all your research on radiant barriers, you've probably come across the statement many times stating that in order for a radiant barrier to be effective, it must face an air space. Why is an air space required? It's very simple:

If a radiant barrier is sandwiched directly between two other materials touching its surface, heat would be conducted directly through the radiant barrier from the first material to the second material. The second material would then radiate heat from itself as if a radiant barrier had not been used at all. Why?

Aluminum is very poor at stopping conductive heat flow. However, aluminum, of which radiant barrier are composed, have two wonderful properties that work in conjuction with an air space that make it ideal as a radiant barrier material:

• the ability reflect radiant heat that travels across an air space to its surface (factor called "reflectivity"), and
• the inability to emit radiant heat from itself across an air space (factor called "emissivity").

"Reflectivity" is the the amount of radiant heat that a material "reflects" (i.e. does not absorb). RadiantGUARD™ radiant barrier products reflect 97% of the radiant heat when facing an air space.

"Emissivity" is the amount of radiant heat that a material "emits" (i.e radiates) from itself. RadiantGUARD™ radiant barrier products emit only 3% of radiant heat when facing an air space.

Reflectivity and emissivity factors are inverses of each other and because RadiantGUARD™ radiant barrier products are double-sided, you only need to achieve an air space on one side of the radiant barrier. However, when possible, most consumers feel better protected by achieving an air space on both sides. Why not - it certainly doesn't hurt.