What Is Radiant Barrier?

A radiant barrier is installed under the rafters of an attic to reduce heat gain in the summer and heat loss in the winter. Traditional insulation is installed on the floor of the attic to further improve energy efficiency.

What Is Radiant Barrier?

A radiant barrier insulation reflects thermal radiation, reducing heat transfer between walls, roofs, or attics. This makes buildings more comfortable and energy efficient by reducing the amount of heat that passes through the roof, walls, and floors. When installed in an attic, studies have shown a reduction of as much as 30°F!

Radiant barrier insulation usually uses reflective materials like aluminum foil, to create a shield against radiant heat. You can install it directly on the surface or add a layer of air or another insulating material in between.

Reflectivity (Emissivity)

The Department of Energy (DOE) states that a product must have a reflectivity rating of 90% or higher and an emissivity rating of 10% or lower to officially classify it as a “radiant barrier.”

Reflectivity is the amount of radiant heat bounced away from the barrier’s surface that is facing a heat source. Emissivity is the amount of radiant heat leaving the barrier’s surface that is facing away from a heat source.

Higher reflectivity ratings lead to more effective reflection of radiant heat.

Energy Shield USA radiant barriers boast a reflectivity of 95-97% and an emissivity of 3-5%.

Durability

To enhance the durability and strength, our radiant barrier products incorporate a central layer of tightly woven fabric. This ensures they can securely hold staples and nails without tearing or letting them pull through.

Energy Shield USA radiant barriers stand out as the sturdiest materials available on the market. A comparison of our specifications against those of competing products reinforces this claim.

Number of Layers

Misleading information has led many consumers to believe that a radiant barrier with more layers is inherently better than one with fewer layers. However, it is not the quantity of layers that determines the quality of one radiant barrier over another. Current ASTM C1313 testing results should be the primary criterion for evaluating the effectiveness of a radiant barrier. If a supplier cannot provide up-to-date testing information, it should raise some concerns.

Fire Ratings

Like most building materials, radiant barriers must undergo testing to meet specific fire ratings. The ASTM E84 fire test, along with the optional E2599 mounting method, determines the fire rating. This test looks at flame spread and smoke development in the surface burning characteristics.

Two organizations, the National Fire Protection Organization (NFPO) and the Uniform Building Code (UBC), confer fire ratings for building materials based on flame spread and smoke development results:

NFPO’s highest fire rating classification is “Class A.”
UBC’s highest fire rating classification is “Class 1.”

Note: All building materials can burn. Fire rating tests classify how quickly building materials burn.

All Energy Shield USA products meet the highest fire ratings available, either Class A or Class 1, tested under ASTM E84 or the ASTM E-84 with E2599 mounting method. For actual test results, please refer to our specification section listed under each product on our radiant barrier page.

Breathable (Perforated) vs. Vapor Barrier (Solid)

Radiant barriers are available in two forms: breathable (perforated) or non-breathable/vapor barrier (solid).

A perforated radiant barrier contains small holes throughout the product, allowing moisture vapor to pass through. According to ASTM C1313, the material must have a permeance of more than five (5) perms, as determined by Test Methods e96/e96M (Procedure A—Desiccant Method). Energy Shield USA stands out from competitors by using our own equipment to perforate our ES® RFID Radiant Barrier ensuring we meet or exceed these minimum requirements

A non-breathable/vapor barrier (solid) radiant barrier has no holes and serves as a vapor barrier. Per ASTM C1313, the permeance of the material must NOT exceed one (1) perm, as determined with Test Methods e96/e96M (Procedure A—Desiccant Method).

As a general guideline for choosing between a perforated or non-perforated radiant barrier:

Solid Radiant Barrier (non-perforated): radiant barrier installed in a closed wall cavity closest to the living space (like a side wall or cathedral ceiling).
Perforated Radiant Barrier (breathable): radiant barrier installed in an area with air movement (like an attic or house wrap).

NASA Certified

Some companies may assert that their radiant barriers are “NASA certified.” Please Note: although NASA used radiant barrier and reflective insulation technology early on, they don’t officially certify any radiant barrier product or manufacturer.

For more information on our radiant barrier and reflective insulation products, please call us or email us here.