Radiant Barriers - The Perfect Complement to Insulation
So you have plenty of insulation in your attic (but if you don't, check out our radiant insulation system), but your summer cooling and winter heating bills are still higher than you think they should be. (As a general rule of thumb, if you are paying more than $.06 per month, per square foot of home space, you are paying too much for energy. For a 2000 square foot home, that means you are spending too much if you are paying more than $120, on average, for gas and electric bills combined.) What can you do?
Radiant barriers may be the answer. The U.S. Department of Energy has estimated that the average southern house should save up to 17% with the installation of a radiant barrier. But what is a radiant barrier?
In order to understand this system, a brief primer on how heat is transferred is in order.
How Heat is Transferred. Heat is transferred from one source to another via three methods of transfer: conduction, convection, and radiation.
Conductive: the transfer of heat flowing through a substance (molecular motion) or to another touching substance. If you touch a pot on the stove, the heat is transferred from the pot to your hand via conductive heat transfer.
Convective: the transfer of heat in fluids, such as rising heated air, steam, and moisture. If you put your hand above a boiling pot, you will feel heat rising from the pot in the form of steam. This transfer of heat from the pot upwards is via convective heat transfer. Convective heat transfer results in warmer air rising and cooler air settling creating a convection loop termed free convection. A Convection loop can also be generated mechanically with the aid of fan or wind and is then called forced convection.
Radiant: the transfer of heat via infrared radiation 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 across an air space to a colder surface is via radiant heat transfer. All materials radiate radiant heat in ranges from 0% to 100%.
Common examples of radiant heat transfer:
· Skin warming up on a sunny day even if the air temperature is not high.
· Roof shingles heated via the radiant heat from the sun.
· Heat radiating from a light bulb.
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 – they 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.
A radiant barrier, on the other hand, reflects and blocks radiant heat energy instead of trying to absorb it. A radiant barrier also reduces convective heat transfer by acting as a physical blockade against convective air flow.
How does a radiant barrier block radiant heat?
The aluminum found in radiant barriers has two properties that enable it to reflect or block radiant heat when at least one air space is provided on one side:
1. Reflectivity = The natural reflectivity property of aluminum facing a heat source across an air space allows the aluminum to reflect radiant heat back to the dir
2. Emissivity = All materials have emissivity's ranging from 0% to 100%. The lower the emittance percentage of a material, the lower the amount of radiant heat radiated from its surface. The naturally low emissivity property of aluminum facing an air space results in very low emittance of heat from itself; it does not radiate much of its own heat from itself. This naturally low emissivity property makes aluminum ideal for use in radiant barriers.
One example of radiant barrier insulation is the space blanket. In 1954, NASA invented a lightweight, reflective material composed of a plastic substrate with a vapor-deposited coating of aluminum. The material, now commonly known as a “space blanket”, is used to protect spacecraft, equipment, and astronauts from thermal radiation or to retain heat in the extreme temperature fluctuations of space.
Another common example found in most kitchens is aluminum foil. When used to wrap a baked potato, aluminum foil will allow the transfer of heat conduction and convection heat while acting as a radiant barrier to inhibit radiant heat transfer. This causes the potato cook to perfection on the inside while protecting the potatoes skin from being burnt on the outside.
Sophisticated radiant barrier applications such as those used on NASA Space Shuttles or simple radiant barrier solutions such as the aluminum foil used to wrap a baked potato all accomplish the same thing; they reduce thermal radiant heat transfer.
Radiant Barriers in the Home When it’s hot outside, the Sun’s radiant heat transfers to the cool air inside and when it’s cold your home’s radiant heat transfers to the cold air outside. Although most homes are built with standard fiberglass, cellulose or foam insulation, they still lose their heating or cooling efficiency due to radiant heat transfer. This means the homeowners lose money on their heating and cooling bills by using unnecessary amount of energy to keep their home comfortable year round.
Our product offers a simple and economical solution for this problem. This barrier reflects up to 97% of the radiant heat your home is exposed to.
Our expert installation crews are knowledgeable, courteous, quick and efficient. We evaluate the needs of each customer on a case by case basis, designing a custom retrofit application of our product for each homeowner’s specific needs. We’ll take the time to answer all of your questions, explain our procedures and help you get the maximum benefit from our product. In most cases, we offer installation within a few days.
Contact us in the Metro Atlanta area for a free consultation and in home energy audit to see if you are a good candidate for our radiant barrier.
