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The builder was blunt and to the point. How much is radiant barrier and how does he install it? If it was up to him, he’d use foam to insulate the home but the customer has been doing research on the Internet and wants him to use radiant barrier under the slab, between the studs and under the rafters.
“If your product’s that good,” he asks, “why haven’t I heard of it?”
The radiant barrier industry has been in existence for at least 50 years, having been developed by NASA to protect astronauts from the extreme temperature swings in space. A cursory history shows dozens of companies marketed the product with varying degrees of success. One company tried to hasten its acceptance through multi-level marketing.
But with building codes requiring higher and higher multiples of R-value in a misguided attempt to “save and conserve” energy, it has been the end-user, the consumer, who has kept the radiant barrier industry alive and growing. Those who do their homework need no convincing that the product produces tremendous energy savings. Those new to the concept invariably come back to the standard question: what is the R-value?
R-value, to the vast majority, has always meant effectiveness. The higher the R-value, the more insulating value a product has. In the public’s mind, thickness equates proficiency. If a consumer really wants to save money on heating and cooling, then buy more insulation. Many consumers, however, began to see an inherent disconnect with the conventional wisdom.
Why, for example, was an attic 300 degrees or hotter in the summer? Why did their air conditioner run late into the night even though the sun had set and the outdoor temperature had fallen? And why did their floors feel cold in the winter?
The radiant barrier industry continues to explain how its product works even as it gains popular acceptance. There are three kinds of heat: conduction, convection and radiant. In the summer, when a consumer wants to keep cool, the heat traveling from the sun’s energy waves (radiant) try to get into the house. This radiant heat comes through the roof and into the attic where it is absorbed and delayed by traditional insulation. How long the heat is delayed from entering the structure is measured in R-value. That is what R-value is, a unit of resistance.
Radiant barrier reflects the sun’s energy waves. As the waves come through the roof, they strike the radiant barrier and are reflected back out the way they came in.
In the winter, the majority of the heat loss is also radiant. The radiant barrier reflects the heat trying to escape from the home back into the structure.
As radiant barrier struggles to be accepted by builders, the radiant barrier industry has developed several products that measure, when combined with traditional insulation, acceptable R-values. Straight radiant barrier is used in the attic because it is perforated and will not “sweat” or cause condensation and resultant mold or mildew. A “bubble” reflective insulation was developed for walls, basements, crawl spaces. It is especially effective with the increasing popularity of radiant floor heating.
Last year, the US Department of Energy (DOE) concluded a new radiant barrier study that tested the performance of radiant barrier in the following attic assemblies:
- Control (no radiant barrier)
- Radiant barrier applied directly to OSB sheathing
- Radiant barrier applied to the underside of the rafters
- IRCC sprayed to the underside of the rafters and OSB
The attic assembly was built to code with rafter spacing, ventilation and insulation, wrote Andre Desjarlais of the Oak Ridge National Laboratory. The large-scale climate simulator tested the attic at temperatures simulating both summer and winter to calculate savings for both heating and cooling. High-power heat lamps were used to simulate the solar load on the roof assembly.
The results, Desjarlais wrote, were similar to previous tests performed on radiant barrier:
- The attic without radiant barrier had the highest heating and cooling costs.
- The OSB with the radiant barrier had a 33 percent improved cooling and 10 percent improved heating.
- The rafter-applied sheet radiant barrier had a 50 percent improved cooling and 10 percent improved heating.
- The IRCC spray had just 20 percent improved cooling and no improvement in heating from the control.
In conclusion, the DOE stated that “going to the added labor in installing a radiant barrier under the rafters can result in greater savings.” The DOE also added that this particular experiment did not have A/C ducts in the attic and homes with attic ducts “could see even greater savings in the summer.”
What is interesting about this test, from the radiant barrier industry point of view, is that the reason the DOE conducted it to begin with is because it states that “radiant barrier is finding its way into more and more building codes, like California Title 24.”
The radiant barrier industry, recognizing it still has millions of homeowners to convert, has now sit its sights on major energy consuming industries. To major industries that consume millions of dollars in energy, any percentage of energy savings could be substantial.
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Herman Torres is a former newspaper reporter and photographer with the Fort Worth Star-Telegram. He has watched the radiant barrier industry develop over the past 20 years. He is currently executive director with Innovative Insulation, Arlington, Texas. To learn more, visit www.radiantbarrier.com.