Radiant Barrier Offers Timeless Roofing Innovation

CodeWatcher LP history

Radiant barrier is used on hundreds of thousands of homes each year and continues to be a valuable material for creating more energy-efficient structures.

Most builders that operate in the Sunbelt regions of the United States are likely familiar with radiant barrier, an aluminum-faced building material used primarily to reduce cooling and heating energy usage in a home. Though the product has been on the market for over two decades, the science behind radiant barrier can be perplexing. Whether you’re a builder who has been using radiant barrier for years or you’re completely unfamiliar with the product, all builders can benefit from having a basic understanding of the history and building science behind radiant barrier.

Brief History of Radiant Barrier

The use of radiant barrier dates all the way back to the 1940s when the president of Infra Insulation, Alexander Schwartz, produced a commercial radiant barrier product that was designed to “conserve winter fuel” and “promote summer coolness” according to the company’s marketing material. The product was a huge hit among architects and builders. Later, in the 1950s, Infra Insulation introduced a similar product to consumers that was marketed as being easily installed by anyone with a staple gun.

These days, radiant barrier is used on hundreds of thousands of homes each year and continues to be a valuable material for creating more energy-efficient structures.

Shaddock Homes is a Dallas-based home builder servicing 15 communities in the Dallas-Fort Worth, Frisco and Plano areas. As a part of its energy-efficiency package, Shaddock Homes has included LP TechShield sheathing on all of the homes it has built in the past six years. According to Shaddock Homes’ Director of Purchasing Bill Pierce, LP TechShield sheathing helps contribute to a home’s value, livability, and affordability. “At the end of the day when homeowners get their utility bill, it will be lower due in part to LP TechShield sheathing.”

Types of Radiant Barrier

Radiant barrier can come in the form of single-sided foil on a backing material such as kraft paper that is often reinforced with a type of mesh to prevent tears. It can also come in the form of double-sided foil with reinforcement such as cardboard or a polyethylene sheet between the foil.

Prior to the early 1990s, the most common way to install a radiant barrier in new construction was to take a roll of radiant barrier and drape it over the tops of the rafters and staple it into place.

Benefits of Radiant Barrier Sheathing

Twenty years ago, LP Building Products introduced the first radiant barrier sheathing, branded as LP TechShield Radiant Barrier Sheathing. The product is made by laminating an aluminum-faced overlay directly to oriented strand board (OSB) roof sheathing. The sheathing is available in standard sheathing sizes and thicknesses, making it ideal for new home construction. With the foil facing into the attic space, it is installed just like conventional roof sheathing and requires no additional labor. LP TechShield sheathing also uses patented VaporVents technology. This technology is an incising process designed to release moisture trapped in the sheathing without affecting radiant barrier performance.

Over the years, architects and builders have begun to take note of the importance of controlling heat migration in and out of the structure. Since it launched in 1998, LP TechShield sheathing has grown in popularity and has since been installed on 2.4 million homes across the United States.

Understanding Heat Transfer in the Attic

Understanding how installing aluminum foil facing downward in your attic impacts heat transfer into your home’s living space isn’t intuitive for most. All three modes of heat transfer (conduction, convection and radiation) come into play, and it’s necessary to have a grasp of how all three play a part in the role of radiant barriers.

When solar radiation hits a home’s roof, the energy is either reflected or absorbed. Most roofing and cladding materials absorb, rather than reflect, a large portion of the sun’s radiation. The measure of absorption of any material is referred to as emissivity, which is a number between zero and one. Materials with high absorption will have high emissivity values close to one. Materials with high absorption will also readily release or “emit” that energy as well, always moving from high to low temperatures. Materials that reflect, rather than absorb, radiant energy are said to have low emissivity (low-e) surfaces and therefore will also not readily emit that energy.

The energy that is absorbed by the roof quickly transfers via conduction and elevates the temperature of all of the materials in the roof deck assembly. As these materials are now warmer than the air surrounding them, they will begin to emit that energy away and into your attic space. The energy that is radiated off the bottom side of your wood (high emissivity) sheathing will then begin heating all of the materials in your attic, including your attic floor insulation, HVAC equipment and ductwork. Convection forces will help move the energy from these materials into the air, and as this process continues throughout the day your attic temperature will quickly elevate. All along, conduction forces will drive this heat energy, from high to low temperatures, through your insulation and into your living space.

The inclusion of a radiant barrier system significantly disrupts this heat transfer process. The highly reflective aluminum surface has very low emissivity, typically .05 or less. Installed on the bottom side of the roof sheathing it helps to limit the heat energy in the sheathing panel from radiating into your attic (hence, radiant barrier), lowering attic temperatures by up to 30 degrees Fahrenheit during the heat of the day. A lower attic temperature then reduces the conductive forces pushing heat energy through your insulation and into your living space, helping to lower your summer cooling costs.

During the winter months, the heat flow is reversed and now moves from your living space and into your cold attic. Heat that escapes to the top of your insulation both radiates into your attic space and is pulled away through convection forces (air movement). In these conditions radiant barriers work by helping to reflect a portion of the radiated heat back into the insulation, slowing the rate in which heat energy is lost.

A common misconception is that radiant barriers hurt a home’s energy efficiency during the winter months by potentially reducing the warming effect of solar radiation. Although radiant barriers are not as effective at reducing winter heating costs as they are at lowering summer cooling costs, studies have found that they are typically not detrimental. This is due to the shortened winter days, lower angle of the sun, and the overall reduction in solar radiation present during the winter.

The Value of Radiant Barrier Today

Several states have incorporated radiant barrier systems into their building code. In California, builders can use radiant barriers to meet Title 24 building code, a regulation that aims for all residential structures to be Net Zero by 2020. In Florida, radiant barrier is included within the performance option of the 2017 energy code, specifically R405.7. Radiant barrier is also included in prescriptive provisions at the municipal level of Texas cities such as Austin, Dallas, San Antonio and Houston. Radiant barrier can also be used to lower HERS (Home Energy Rating System) scores in zones 1–5 by as much as three points (greatest impact in lower climate zones).

As national and state building officials continue to place greater emphasis on energy efficiency and sustainable living, radiant barrier has proven to be a revolutionary product innovation and a staple in energy-efficient home building.

Kayla Boyce is the Product Manager for the LP TechShield sheathing, LP TopNotch sub-flooring, and LP Legacy sub-flooring product lines at LP Building Products.