Radiant Barrier

A radiant barrier insulation system is a system of metalized film that is usually installed in attics or walls of a building as a radiant barrier’s reflective properties often offer a cost effective and permanent way to reduce energy costs. Simply put, a radiant barrier insulation system is designed to reflect radiant heat energy.  Without one, your home absorbs unwanted solar heat in the summer and lets warm air (that you paid to heat) escape in the winter. Another positive feature of state of the art radiant barrier reflective insulation systems is that they are unaffected by humidity and as such perform at consistent levels regardless of how low or high the relative humidity is making the radiant barrier systems very efficient.

Most people today are familiar with the traditional insulating materials of cellulose, fiberglass, Styrofoam & rock wool. All of these products use their natural absorption properties to insulate a space from convective & conductive heat transfer.  By contrast, only a radiant barrier system addresses radiant heat transfer. Radiant heat transfer causes unwanted heating of the air and the home’s materials in the summer when the sun is beating down on the roof and allows warm air to escape in the winter – an unwanted condition as you have paid to heat that air. Let’s look at the charts below to explain:

In the bar chart below the Yellow bar represents Convective heat transfer, the Blue bar represents Conductive heat transfer and Red bar represents Radiant heat transfer.

As can be seen in the center diagram above, in winter, approximately 50-75% of heat loss is through the ceiling/roofing system and the diagram to the right shows that approximately ~65-80% of the heat loss through the walls is radiant. But even more revealing is the diagram on the left. This diagram shows that during the summer up to 93% of the home’s heat gain is radiant heat gain. Depending on traditional fiberglass or cellulous insulation alone to control against heat gain or loss isn’t enough.  That’s because the insulation value of thin layers of fiberglass or bunched cellulous materials have almost no effect on radiant energy gain or loss.  Additionally, both types of insulation are affected by changes in humidity which can have a large effect on their insulating abilities. How much can humidity affect their performance? Well, a change of as little as 1½% in the moisture content of fiberglass insulation will result in approximately a 36% decrease in the insulating performance. By contrast state of the art radiant barriers are unaffected by humidity and continue to perform at full insulating value regardless of humidity.

There are many different Radiant Barrier insulation products and systems that can be designed to match a variety of different applications. Matching the correct product/system to specific conditions is extremely important to maximize performance. Consulting a qualified Home Performance Contractor certified in scientifically determining a home’s needs for optimal insulation solutions is your first step in determining if a Radiant Barrier insulation system is something that can help improve the comfort and energy efficiency of your home.  

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