What is HeatBloc-75? HeatBloc-75 is an aluminum colored, water based, low emissivity (low-e) coatings. When applied to building materials such as plywood, OSB or plasterboard, HeatBloc-75 lowers their surface emissivity to 0.25 or lower, thereby blocking 75% of the radiant heat trying to enter the home. It is classified by ASTM as an Interior Radiant Control Coating (IRCC) and may be effectively used as an interior radiant barrier.

How does Heat-Bloc75 work? HeatBloc-75 radiant barrier works by changing the emissivity of the surface where it is applied. Building products such as wood, brick, and plasterboard have high emissvities (0.7-0.95). When heated, they radiate most of their heat to cooler surfaces by allowing the heat to penetrate the roof into the attic and from the attic into the house. HeatBloc-75 lowers their surface emissivity to 0.25, lessening their ability to radiate heat and therefore letting less heat penetrate the roof into the attic.

What is 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 ravels 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 barriers address heat flows by radiation. A radiant barrier is a low-e surface placed in the path of thermal radiation that blocks heat transfer.

Does HeatBloc-75 degrade over time? HeatBloc-75 does not loose its effectiveness over time like some radiant barriers. Foils can tear and require the staples to penetrate the barrier. Foil chips can accumulate dust, which diminishes their effectiveness.

Is HeatBloc-75 permeable to water? Yes! HeatBloc-75 allows water vapor to permeate, and does not trap water vapor within roof decks or sidewalls. This is very important in attic conditions.