What is a Radiant Barrier?
Heat penetrates buildings in three ways: conduction, convection and radiation. Radiation is the transfer of heat by electromagnetic waves known as thermal radiation. Thermal radiation is a form of invisible light that travels through the air from a warm to a cool surface. Warm surfaces, such as roof decks warmed by the sun, will radiate or emit their heat to cooler interior building surfaces. Radiant heat barriers address heat flows by radiation. A radiant heat barrier is a low-e surface placed in the path of thermal radiation that blocks heat transfer.
What is Emissivity?
Emissivity is the ability of a surface to radiate or emit energy in the form of long wave electromagnetic radiation. It is represented by a value from 0 to 1. The closer the value is to 1, the less effective the surface is at impeding radiant heat transfer. Wood has an emissivity of 0.90. Thus, when wood is heated above the temperature of surrounding surfaces, it will tend to transfer 90% of its heat energy by radiation.
Flagler Foam Insulation is proud to offer two types of radiant barriers:
HeatBLOC® is an aluminum colored, water-based, low emissivity coating typically applied in the attic to the underside of the roof deck by spraying or rolling it on. HeatBLOC® radiant heat barrier works by changing the emissivity of the surface where it is applied and helps by reflecting or blocking 75% of the radiant heat instead of allowing it to be absorbed through the roof deck into your home. While they are most effective at lowering cooling costs, studies performed by the University of Kansas have showed a 15% reduction in heat loss through the attic when radiant barriers are used. HeatBLOC® allows water vapor to permeate, and does not trap water vapor within roof decks or sidewalls. This is vitally important in attic conditions because radiant heat barriers only control radiant heat loads. Good attic ventilation helps control convection loads. Together they raise the comfort levels and lower cooling
For masonry walls we use Fi-Foil’s® AA2 Vapor Shield is a multi-layer reflective insulation intended for use on furred-out masonry walls. The inside layer is aluminum foil. The outer layer is natural kraft paper coated with polyethylene, internal expanders separate the paper from the foil creating a 3/8″ reflective air space. When installed on furring strips spaced 16″ or 24″ on center, a second reflective air space is formed. This air space is dependent upon the thickness of the furring strip selected. AA2 Vapor Shield is available in Standard & High-perm versions or perforated for applications not requiring a vapor retarder.