Radiant barriers 101
What exactly is a radiant barrier?
A radiant barrier a thin barrier that is placed in your attic to prevent heat from penetrating into your system. Usually these barriers are made from a foil type insulation that acts as a reflective surface. This reflective insulation system offers a permanent way to reduce energy costs. Radiant barrier foil insulation systems BLOCK heat energy instead of absorbing it. A pure aluminum barrier is unaffected by humidity and will continue to perform at a consistent level no matter how humid it may be. This insulation system consists of a layer of foil facing an airspace and is installed in the envelope of a building. In order to fully understand how radiant barriers work and how they can benefit you, you must first understand how heat is actually transfered.
How is Heat Transfered?
- Conduction: the transfer of heat flowing through a substance (molecular motion) or to another touching substance. If you touch a pan on the gas stove, the heat is transferred from the pot to your hand via conductive heat transfer.
- Convection: the transfer of heat in fluids, such as rising heated air, steam, and moisture. If you put your hand above a cup of coffee, you will feel heat rising from the mug in the form of steam. This transfer of heat from the mug upwards is called convective heat transfer. Convection results in warmer air rising and cooler air falling, creating a loop termed "free convection."
- Radiation: the transfer of heat via infrared rays that are invisible to the naked eye and unaffected by air currents. If you step outside on a windy sunny day, you will feel the sun's heat rays on your face. This transfer of heat from a heated source to a colder surface is called radiant heat transfer. All materials radiate heat in ranges from 0% to 100%.
Most people are familiar with traditional insulating materials such as fiberglass, cellulose, styrofoam, and rock wool. These products absorb or slow down convective and conductive heat transfers to insulate. These types of insulation do not BLOCK heat - only slow it down. Therefore, after a period of time, 100% of the heat absorbed would eventually transfer through the insulation. The rate in which this heat eventually transfers through an insulation material is the material's R-Value.