What to Believe About Reflective Insulation
I've been in the industry since 2002 and I must admit that until recently I didn't completely understand all aspects of this unique and versatile product. It's no wonder many are confused. I will simplify what I found to be difficult concepts to grasp. After reading this page, you'll better understand reflective insulation and other insulation types - Facts vs. Fiction.
Fact: The stated R-value of a reflective insulation system is accurate.
Fiction: The stated R-value of fiberglass and cellulose insulation is accurate.
Is the Stated R-value of A Reflective Insulation System Accurate?
Yes. The R-value of reflective insulation and mass insulations is based on the same fundamental equation - (The ability to stop heat transfer). The R-value of reflective insulation is measured as a system. The best system consist of two reflective surfaces surrounding an inner substance (core) plus two trapped airspaces. If you know the system measured (parameters of test), the R-value you're using is real.
The confusion about the R-value is that people fail to understand it's a system that is measured rather than just the product. It's actually a better form of measurement when you think about it. It answers the question, what will be the R-value when applied in an application (roof for example).
- Reflective insulation R-value is measured as a system.
- It has a center (core substance).
Example - Prodex Total Reflective insulation has an R-value of 16.
13/64 inch (approx. 3/16") - 5mm closed cell polyethylene foam covered on both sides with .0012 inch (0.03mm) aluminum foil facing.
The R-value was measured under the following parameters:
24-inch on center 2" x 6" wood assembly. Roof application. Test Method ASTM 1116. Airspace of 2.64 inch on each side of product. Heat flow direction down.
Best Definition of Reflective Insulation
An insulation system that reduces the transfer of heat across air space by the use of two surfaces having high thermal reflectance and low emittance (typically metalized film or aluminum) + plus an inner substance (mass insulation) + plus trapped airspaces.
Most definitions, even those on .org websites fail to mention the inner substance (mass insulation) that is in between the two reflective surface layers. This is the cause of much of the confusion. Without the inner substance, (foam, fiberglass, wool or mylar bubbles) it is not reflective insulation - it is only a radiant barrier.
This bears repeating " Without the inner substance, (foam, fiberglass, wool or mylar bubbles) it is not reflective insulation - it is only a radiant barrier.