- DEFINITION
- CONSIDERATIONS
- COMMERCIAL STATUS
- IMPLEMENTATION ISSUES
- GUIDELINES
- The reflective surface is on one side and faces downward into the attic.
- Can be draped over the top of the roof rafters. In this application, allow the material to drape downward 2 inches or so between the rafters to create an airspace on both sides of the radiant barrier material.The radiant barrier material can be applied to the underneath side of the rafters. In this location, an airspace will be present on both sides of the material and can be effectively combined with a ridge and soffit venting system.
- One layer of a typical radiant barrier material will block 95% of radiant heat gain. A second layer for the purpose of blocking additional radiant gain blocks less than 5%.There is an added R-value due to dead air spaces between the layers.
- Typically applied on the underside of existing roof decking.
- Radiant barrier material can function as a vapor barrier. Therefore, use only perforated material in this application.
- Dust accumulation on the radiant barrier material’s surface inhibits its performance. This is unavoidable in the flat location over insulation.
- When the material is placed flat on the attic insulation, it can also be punctured or torn during any service work that may need to be done in the attic (i.e. ductwork).
CSI Numbers:
07194 Radiant BarrierDEFINITION:
A radiant barrier is a layer of metallic foil, reflective paint, or other reflective material that blocks radiated heat, assisting in the energy performance of a buildingCONSIDERATIONS:
A radiant barrier is used in our area principally as a cooling strategy. Buildings gain heat in three ways – conduction, convection, and radiation. A radiant barrier is useful in preventing heat gain from radiation. Emissivity is an indication of a surface’s ability to emit heat by radiation. The lower the emissivity, the better the radiant barrier qualities of a material. Emissivity is measured on a scale of zero to one. Most foil type radiant barriers have an emissivity of 0.05 or below, which means 95% of the radiant heat is being blocked. A radiant barrier is typically placed beneath roofs in our area to block the heat gain radiating from hot roofs. Temperature reductions of 10 degrees or more are typical during peak summer days. The reduction of attic temperatures is considered less important in highly insulated attics (R-30 and higher), in respect to conduction through the ceiling. If air conditioning ductwork is located in the attic, lowering the attic temperature reduces heat gain on the ductwork.Commercial Status | Implementation Issues | ||||||
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T E C H N O L O G Y | S U P P L I E R S | C O S T | F I N A N C I N G | A C C E P T A N C E | R E G U L A T O R Y | ||
Radiant Barrier | ![]() | ![]() | ![]() | ![]() | ![]() | ![]() |
![]() | Satisfactory |
![]() | Satisfactory in most conditions |
![]() | Satisfactory in Limited Conditions |
![]() | Unsatisfactory or Difficult |