Contractors love selling "Liquid Radiant Barrier." It is cheap, easy to spray through a paint gun, and allows them to finish an attic in 2 hours instead of 2 days. The problem? Pushing liquid silver paint onto porous wood decking fails the fundamental laws of thermodynamics.
| Barrier Type | Reflectivity / Emissivity Rating | Installation Profile |
|---|---|---|
| Silver "Radiant" Spray Paint | ~75% Reflectivity | Sprayed directly onto wood. Wood absorbs the paint unevenly, leaving massive dull spots. Requires perfect 10-mil thickness to even reach 75%. |
| Woven Aluminum Foil Roll | 97% Reflectivity | Physically stapled. Zero variations in thickness. Guaranteed uniform 97% block against radiant heat forever. |
Emissivity vs Reflectance
A true foil barrier physically reflects 97% of the sun's radiation back UP through the roof. Liquid paints rely heavily on "Low Emissivity"—meaning they absorb the heat, but are slow to emit it into the attic below. In a 12-hour Dallas summer baking cycle, the paint eventually saturates and the heat dumps inward anyway.
We only install physical, poly-woven, double-sided aluminum foil stapled to the rafters. If a contractor offers you a spray-paint barrier, they are selling you a placebo.