Radiant Barrier With Fiberglass Insulation In Roof Rafters

How to install radiant barrier on attic rafters in 5 steps.

Radiant barrier with fiberglass insulation in roof rafters.

The most common material used for an insulating metal roof is fiberglass batts or glass mineral wool. The batts are located side to side on the rafter of the roof. To avoid condensation issues a perforated radiant barrier may be the best choice for this application. The details involving the logistics of installing a radiant barrier go beyond the scope of this article comparing roof and ceiling insulation.

When the sun heats a roof it s primarily the sun s radiant energy that makes the roof hot. You want to add the foil on all surfaces that make up the roof but you also need to keep vents open and clear of the foil. Much of this heat travels by conduction through the roofing materials to the attic side of the roof. The goal of adding a radiant barrier in your attic is to cover as much of the underside of the roof as possible.

Both materials make a great physical barrier between the interior building and the metal roof. Radiantguard radiant barrier foil insulation installed in an attics can reduce attic temperatures by up to 30 degrees when stapled with a staple gun to the underside of roof rafters by reflecting up to 97 of the radiant heat that strikes its surface thereby reducing heat transfer from the attic to living spaces resulting in lower utility bills. Installation methods include radiant barrier draped over the rafters applied directly to the roof sheathing stapling to the bottom of the rafters and even laying radiant barrier on top of the attic floor insulation. I ran across multiple studies during my research that found deductions in heat transfer from the conditioned space especially when the radiant barrier was layed across the attic floor over the insulation instead of being stapled to the rafters.

The radiant barrier should be installed in a manner to minimize dust accumulation on the reflective surface. However you should at least know that the most effective radiant barrier location is either below the bottom chord truss or underneath the roof sheathing. The hotter the attic the more the heat moves down to the cooler building below.