Radiant Barrier With Fiberglass Insulation In Roof Rafters

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.

Radiant barrier with fiberglass insulation in roof rafters.

The most effective radiant barrier sheathing is a structural roof sheathing panel which consists of an osb panel with heat reflecting foil laminated to one side. How to install radiant barrier on attic rafters in 5 steps. When the sun heats a roof it s primarily the sun s radiant energy that makes the roof hot. The most common material used for an insulating metal roof is fiberglass batts or glass mineral wool.

Unlike insulation like fiberglass or foam neither radiant barriers nor the roofing materials hold radiant heat. The hotter the attic the more the heat moves down to the cooler building below. Much of this heat travels by conduction through the roofing materials to the attic side of the roof. To avoid condensation issues a perforated radiant barrier may be the best choice for this application.

The goal of adding a radiant barrier in your attic is to cover as much of the underside of the roof as possible. 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. 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.

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 radiant barrier reflects 95 of the radiant heat back to the roofing materials which then emits over 90 of the heat out the roof almost instantly.