The laws of physics tell us that there are three forms of heat transfer. They are convection, conduction and radiation. Convection is the movement of air upwards or sideways carrying heat toward a cooler point. Convection is visible as wavy lines above a hot road. In buildings, convection currents are more of a concern in the winter because we heat the interiors. During winter months convection can account for up to 45% of heat transfer, but almost nothing in the summer. Conduction occurs when heat travels to cold. It carries energy when two building materials come in contact. The roof is connected to the trusses, the trusses are connected to the drywall, etc. Conduction only accounts for between 5% and 7% of the heat transfer into a building. Radiation is electromagnetic waves that can only be seen as part of a rainbow. It travels at 186,000 miles per second. Its infrared frequencies travel in all directions, seeking a cooler object to strike and then that object generates heat. Microwave ovens work on the same principle, in that they heat the object, not the air. Radiant energy passes through most standard building materials including metal, wood, asphalt and fiberglass. Radiant energy is responsible for between 45% and 93% of the heat transfer into - or out of - a building.


Before we talk about Low-E insulation we need to define two thermal values. The first being “R” the second being “E”. An “R” value is technically described as resistance to conductive heat flow. Remember that conduction only accounts for up to 7% of the heat transfer. “R” values play such a small part in stopping the heat that is transferred into your building, maybe we should ask ourselves why we put so much importance on high “R” values.

The “E” in Low-E stands for a specification known as emissivity. Simply put, emissivity is the ability of a material to take energy applied to one side and re-radiate it off another. If you heat the inside of a cast iron radiator you can feel the heat come off the outside. Iron has an emissivity of approximately 85%. So 85% of the inside temperature is transferred to the outside. The emissivity of wood is approximately 92%. The emissivity of steel is approximately 80%. The emissivity of asphalt is approximately 98%. The emissivity of glass, the most popular insulating material, is approximately 95%.

It is easy to conclude that we have a major problem here. We can even make matters worse by throwing moisture into the mix. If these materials become wet from condensation or exterior leakage, conductive transfer of heat or cold can become accelerated and further reduce insulation performance.


If you remove a cooked turkey covered with an aluminum foil tent from the oven and place your hand directly over the foil; you notice very little heat. If you were to put your hand inside where the turkey is, the temperature would be at least 350 degrees and you would severely burn your hand. Pretty neat stuff that aluminum foil. You might ask yourself, “why doesn't someone make a building insulation that can stop heat transfer like the aluminum foil over my turkey?”


Created by Environentally Safe Products in New Oxford, Pennsylvania, the primary function of Low-E insulation is to reduce the transfer of radiant energy. The materials that Low-E insulation is made from are polyethylene and aluminum. Our standard product consists of a ¼'' thick extruded, micro-cell polyethylene core that is waterproof, flexible and strong. The exterior surfaces are covered with polished reinforced aluminum. Our patented Low-e insulation does have a tested “R” value of 10.74, but more importantly, it's aluminum surfaces have an emissivity of 3%, which means that 97% of radiant heat frequencies are stopped and reflected back to their source.

Most common or conventional insulations do their best to slow down the heat transfer, but no matter how thick they are, they have almost no ability to reflect radiant energy. In fact, they act like a battery, storing heat, then re-radiating it. Mass insulations can also store moisture which further reduces their capabilities to resist the transfer of thermal energy. For these reasons, by mid afternoon in the summer, buildings using only mass type insulation can become unbearably hot. Even large air conditioning units battle against the odds all day and put a serious drain on utility companies not to mention your wallet.

By addressing only “R” values, manufacturers and consumers have ignored the major problem facing insulation today. You guessed it, ...radiant heat transfer. By using Low-E, you can reflect the heat back to the source. Therefore, buildings become more temperature consistent and more economical to operate, no matter what the season.


Low-E insulation is produced in roll form and comes in widths from 16 inches to 6 feet. The average roll covers 500 square feet and weighs under 24 pounds. It is designed to be easy to handle and install. It also comes in several different thickness' ranging from 1/8 inch to1/2 inch. The facings can be both sides foil or one side foil with the other side white polyethylene film. We also have an extended staple flange option that is useful in certain installations.


Because Low-E also acts as a vapor barrier, moisture problems are all but eliminated. Insects, birds and other vermin won't find it to be a suitable habitat, and it is completely safe to work with. There are no fibers to stick in your skin or eyes, and no carcinogens to inhale. Because of it's construction, it will also seal around screws or nails that puncture it during installation. Low-E also has sound deadening characteristics similar to mass insulation.

Besides roofs and walls, Low-E insulation can be used to insulate pipes, ducts, cars, and trucks. Water heaters, crawl spaces, water beds, boats, basements, and foundations. Low-E insulation can be used under concrete, in radiant floors and wall heating applications, planes, buses and trains. The possibilities are endless, most of us here cut some for inside our snow boots in the winter. Oh, I almost forgot! Low-E all but stops conductive and convective heat transfer also.


A staple gun and utility knife are the only tools required for frame installation. Standard speed fasteners and tape are generally used in steel construction. Low-E is being used as a stand alone insulation and is being installed along with mass insulation. Because of its obvious advantages, Low-E insulation is rapidly becoming the preferred choice of top builders today.

Pittsburgh Radiant, LLC
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Last update 15 January 2008