What is radiant barrier roof decking?
How it works
On a summer afternoon, Georgia shingles get very hot and the deck under them radiates heat down into the attic, warming the ductwork and insulation. Shiny aluminum has very low emissivity, meaning it gives off little radiant heat, so with the foil facing down into an open air space much less heat reaches the attic. The U.S. Department of Energy notes that radiant barriers are most effective in hot, sunny climates and especially when air conditioning ducts run through the attic, which describes a lot of Georgia homes.
What it does not do
- It does not replace insulation or ventilation. It works alongside both.
- It needs an air gap. Foil pressed against insulation loses most of its benefit.
- It does little for winter heating, though it does not hurt.
Cost and when to use it
Radiant barrier sheathing costs somewhat more than plain OSB. On new construction or a full redeck it is an easy upgrade. During a normal reroof only the replaced sheets would be foil faced, so homeowners who want the benefit on an existing house usually add a foil product stapled to the rafters from inside. Some builders use it to satisfy energy code options; your local building department can tell you how it is treated.
A note on shingle temperatures
Reflecting heat back up raises shingle temperature slightly. If you are planning a roof over radiant barrier decking, check the shingle maker's guidance and keep attic ventilation strong. See attic heat and shingles and OSB vs plywood roof decking.