Radiant barriers work by reflecting heat instead of absorbing, or slowing the flow of heat like other forms of insulation typically do. They are generally used in homes, usually in the attic, but can also be found in some other common applications such as a sun screen for the windshield in your car.
How Do They Work?
Heat naturally flows from warm areas to areas that are cooler through three different methods: radiation, convection, and conduction.
- Radiant heat is emitted from a source and travels away in a straight line heating up any surface that it hits. This is the warmth we feel from the sun on a clear day.
- Convection happens when heat is transferred into a gas or a liquid, for example air or water. When the air or water becomes less dense when it is heated and rises, while the air or water which has cooled becomes more dense and sinks. This rising and sinking transfers heat from one place to the other and is called convection.
- Conduction works by allowing the energy to travel through a material, such as when a hot cup of coffee conducts heat through to the handle of your spoon..
Typical insulation materials are effective because they slow down heat conduction, that is the movement of heat through a material. Radiant barriers work instead by reflecting heat. In order to work properly the surface of the radiant barrier must be facing an open air space. Any accumulation of dust on the surface of the reflective area will reduce its efficiency.
In the case of the attic, the roof is primarily heated by the sun’s radiant energy. That heat is then transferred to the attic side of the roof through conduction. Then, the heat on the inside of the roof transfers that heat down into the attic through radiation. That means heating up your ceiling and any ducts or pipes that may exist in your attic. The use of the radiant barrier will reduce the transfer of heat from the underside of your roof to the places in your home that you want to keep cool.
It may be useful to keep in mind that a radiant barrier is most effective when the air is perpendicular to the incoming radiant energy. Interestingly, a radiant barrier produces greater results when there is a greater difference in temperature between the front and back sides.
Some studies indicate that your cooling costs can be reduced by as much as 10% when you use a radiant barrier in a climate which is sunny and warm. Since radiant barriers work better in hot climates than when compared to climates which are cooler, if you live in a place that has cooler weather, it is generally recommended that you opt to install additional thermal insulation as opposed to a radiant barrier.
Types of Radiant Barriers
Radiant barriers are usually made out of a material that is highly reflective. This is usually some type of foil made out of aluminum. It is then adhered to both sides of another material, giving it stability and making it easier to work with.
Radiant barriers are often combined with other types of insulation materials. A Radiant barrier might be found as the facing for insulation Batts that will be used on the floor of an attic.