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Radiant Barriers Go Beyond Insulation For Heat Efficiency

Insulation is one of the highest payback improvements you can make to a building -- at both new construction and remodeling time. Radiant barriers are a new approach with additional heat resistant benefits.

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We hear about radiant barriers in applications such as the heat shielding ceramic tiles on NASA shuttles. And the aluminum foil used on baked potatoes. Those are "radiant barriers" that keep heat in... or out.

Heating air is expensive! Cooling air is also expensive -- so it makes sense that if you don't have to condition air as much, you'll save on your utility bills.

Insulation and radiant barriers are used in buildings to keep heat in during the winter...and keep heat out during hot periods and seasons. But most buildings weren't optimized for energy efficiency in both hot and cold temperatures.

"There's no such thing as heat and cold," my husband told me, "only heat and less heat." Practically speaking. Of course, absolute zero is pretty cold, but in the everyday world of conditioning the air of our homes and workplaces, heat and less heat is a good way of thinking about temperature flow, changes and controls.

That's where radiant barriers and insulation come into a tug of war.

Heat Transfer


Direct heat flow through a solid object like a roof, wall or ceiling.


Heat movement through air that occurs when air is warmed. Warm air expands, becomes less dense and rises.


Movement of heat rays across air spaces from one warm object to another less-warm object. Wood stoves give off radiant heat, for example.

Radiation, Convection and Conduction - 3 Types of Energy

Insulation has been used for several decades to manage building heat. But insulation doesn't deal equally well with all three types of energy.

The summer sun produces a lot of radiation.

So...putting a radiant barrier such as white, cool roofing materials outside your home will reflect much of that sunlight and heat.

Winter heating inside the home produces mostly convection and radiation.

So...putting a radiant barrier of insulation and/or aluminum on top of your insulation will reflect conditioned air (heat) back into the rooms that are cool or heat conditioned.

In essence, the heat flows inside out in the cold winter -- and outside in in the hot summer. Insulation slows the heat movement down, but doesn't stop it's movement.

Foil covered barriers reflect the heat and in essence, stops it from entering the other side of the barrier.

Radiant Barriers Research

The Florida Solar Energy Center at Cape Canaveral has tested radiant barriers in both small scale laboratory andfull scale building models. Their results indicate that radiation barriers provide significant resistance to heat transfer.

Tests by the Oak Ridge Laboratories in Tennessee, and the University of Mississippi support those findings.

Using infra-red thermography, heat transfer has been tested for resistance differences between radiant barriers and insulation. These photos show significant resistance to heat transfer over regular insulation.

Radiant Barriers for Buildings

The bright aluminum surface of radiant barrier products provides insulation properties in two ways:
  • The reflective surface reflects long wave radiant heat that strikes it -- up to 97% of all radiant heat.
  • Close contact, but non-touching, allows reradiation to happen, and when you reduce the amount of heat that "gets through" the radiant barrier, you will have less convection taking place.

Applications for Foil Radiant Barriers and Insulation

Radiant Barriers

Radiant barriers are single layers of foil like, reflective sheets that find applications in:
  • Attics that need additional insulation
  • Under roof decking
  • House wrap
  • Metal buildings
  • Fire walls
  • Vapor radon barriers

Reflective Insulation

Two layers of foil with bubble between the layers is called "reflective insulation" because it provides both dead air space for insulation and reflective foil surfaces.

Common applications of reflective insulation include:

  • Building walls
  • Pre-engineered metal buildings
  • Agricultural buildings
  • Vapor/radon barriers
  • Duct or pipe wrap
  • Crawl spaces
  • Basement walls
  • Water heater wrap
  • Post and beam construction
  • Under concrete radiant heat floors
  • Thermal packaging
  • Automotive

Energy Star Benefits

Energy Star is an established US EPA and DOE program that focuses on energy efficiency of building components, and even entire buildings and their operation.

By combining Energy Star best practices for insulating your building, such as weatherizing the cracks and crannies, and insulating exposed surfaces properly, Energy Star research can help you develop a plan to keep your heat where you want it -- and lower your utility bills!

ENERGY STAR considers insulation to be products or materials that meet the FTC's definition of "home insulation" ("any material mainly used to slow down heat flow") and are used to insulate a whole wall, ceiling, or floor. These products include, but are not limited to: fiberglass, cellulose, mineral wool, whole-wall spray foam, rigid foam board, cotton fiber batts, and foil radiant barrier products.

Tax incentives and utility company rebate programs often include insulation in programs that offset some of the initial costs of installing energy-saving insulation. And by reducing your energy use, you not only save on your monthly utility bill, but reduce the need to generate that energy, which reduces greenhouse gas and heat that impacts our environmental systems and weather patterns. And that saves lives and money in the long term, as well.

Edited by Carolyn Allen
| insulation | energy efficiency | indoor air quality | green building |


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