Ridge, gable and soffit vents are little relief for attics exposed to summer temperatures in southern climates. Radiant heat is responsible for attic temperatures reaching upwards of 140°F. Why are heating and cooling systems often installed in the attic space when it is the hottest and coldest place in the house? Because it is convenient but not the most efficient. With spray foam, the problem is solved.
The “unvented attic” or “closed attic assembly” is the most efficient solution to hot attics. This system involves spraying foam to the underside of the roof line and encapsulating the rafters. It turns an attic into a semi-conditioned space where temperatures will vary only slightly from the conditioned area below. According to building codes, this design is only approved with an impermeable insulation (ref. code commentary IRC 806.4). Only spray foam can satisfy this code requirement. Installed differently than traditional insulations, spray foam moves your thermal envelope up off the attic floor and your utility bills down.
Conduction, Convection and Radiant Heat Transfer
Spray foam protects your home or building from all three types of heat transfer. As an air barrier it prevents convective heat loss associated with air movement through walls and roof lines as well as convective currents occurring within the wall cavity. Thermally, spray foam’s effective R-value is a true combatant of conductive heat loss. And although spray foam is nothing like a traditional foil-faced radiant barrier, along the roof line 5 ½ inches of low-density spray foam will not allow heat to ever radiate from its interior facing surface even with 12-14 hours of direct sunlight impeding upon your roof from above.
• Excess heat loss/gain from duct leakage is less of an issue.
• Loose insulation and dust won’t migrate to the living space.
• The “stack effect” is eliminated