Published on April 1st, 2013 | by Guest Contributor
Going Green With Radiant Barriers
People are always looking for ways to cut energy costs on their homes. A popular and efficient way is to have a radiant barrier installation. A radiant barrier is a supplement to your home’s insulation that helps reflect or radiate away transferred heat. The barrier itself consists of a layer of thin aluminum film that fits between the airspace and walls. One good example is between a roof and the attic floorspace.
What is a Radiant Barrier?
A radiant barrier is a thin foil layer of aluminum that has a highly reflective surface. The radiant barrier film sheet or panel, repels radiant heat, such as the sun’s heat on a roof back to its source. They are most often installed in attic spaces or used as a house wrap, particularly in new homes. In the summer, the barrier reduces the transferred heat, and in the winter reduces heat loss. Radiant barriers use low emissivity and high reflectivity to shield against radiant heat. Radiant barrier material has a product rating in the form of an ASTM C1313 classification. They can range from 0 to 1, but a true radiant barrier must have a rating of 0.9, which means it radiates back 90 percent of the heat it comes in contact with.
Radiant Barriers do not function like common insulator materials, like rock wool, fiberglass and synthetic cellulose. They do not slow down heat by absorbing it, but rather reflect it away. Radiant barriers allow only a 10 percent emission of their own heat back to a source across an airspace. The barrier material comes in one-sided or two-side reflective surfaces. The one-sided version has a highly reflective aluminum side and a paper-backed side. If only one side is used, the reflective surface must face toward the open airspace where the heat is generated from. Costs vary, depending upon the manufacturer, but typical expense for a radiant barrier installation runs anywhere from 12 to 40 cents per square foot.
What Constitutes Radiant Heat?
Radiant heat is heat that comes from a source, like a roof, and travels across an open airspace to strike another surface. The heat radiates through the air. Standing outside under the sun, you can feel the heat rays contacting your skin, which is much the same way household heat is travels through the structure. Another example can be seen while standing in the attic of a house. A person can feel the heat bear down on them from the underside of the overhead roof decking.
Positive Case Study Reports
The Florida Solar Energy Center conducted an in-depth study on a test site during a cooling season in summer. It revealed that a properly installed radiant barrier improved the thermal qualities of a test attic space, showing an R value that reached 19. This amounted to a 16 percent reduction in energy usage. The energy reduction directly lowered the energy costs during a heating season of a typical home. The gains in energy savings are significantly improved when a radiant barrier installation is combined with additional R-11 insulation, which ups the performance rating to R-19. By providing a R-19 insulation package with a radiant barrier, the factor increases to the performance levels of an R-30 installation. With a radiant barrier and R19 installation, savings range from 10 to 30 percent.
Summer Cost Saving Benefits
Even with insulation, as much as 93 percent of the sun’s heat enters through the roof and radiates against the unprotected floor boards of the attic. The heat is trapped and held there. As a result, the living space below maintains a much higher temperature, even higher when the outside ambient temperature rises. By installing a radiant barrier you effectively block all the heat that would pass through the attic floor decking. This can cut the energy costs drawn by an air conditioning unit by as much as 50 percent when you lower your settings to compensate for the reduced temperature.
Winter Cost Savings
A Double-sided radiant barrier not only repels unwanted heat but it can actually retain household generated heat within the living space. It does this by blocking it’s escape against its surface, disallowing it to pass into the attic area. Studies indicate that winter heat loss can reach as high as 75% via radiant heat. By keeping living space heat confined, energy costs produced by a heater are reduced significantly. If the heater is electric, the savings can be substantial. You can re-set or re-program your thermostat to a lower temperature so it cycles less frequently.
When your air conditioner or household heater runs less often, it saves on wear and tear on all the components. This amounts to extended life for these units, which can be very expensive to repair and/or replace. Extended running heats up and wears shaft bearings and electrical motors, and by cutting their running time you save not only in the long run but decrease the amount of maintenance and service visits required to keep them operating properly.
This is a guest post from Benjamin Franklin Plumbing Minneapolis, a team of plumbers in Bloomington, MN who specialize in green plumbing updates for residential homes and commercial businesses. Green Living Ideas was not compensated for this post. Image from Green Energy of San Antonio.