By: Robert J. Aresty, SOLEC-Solar Energy Corporation
For homes in southern climates, radiant barriers and interior radiation control coatings (IRCCs) are an effective, low cost way to improve energy efficiency in homes and conditioned buildings. Any structure that relies on air conditioning for a large portion of the year can benefit from this technology as a way to reduce utility usage in new construction or retrofitting existing buildings.
They work by affecting heat flows into the building. Radiant barrier and IRCC efficiencies are driven by a characteristic called emissivity, or thermal emittance. Emissivity describes the ability of a surface to radiate or “emit” heat. Everything has a prescribed emissivity based on its chemical makeup, from human skin to leaves to rocks to roofing materials. The higher the emissivity, the better able that surface is to release its stored heat energy by radiation. The lower the emissivity, the less able it is to release its stored heat energy by radiation.
Most building materials have high emissivities, i.e.: roofing shingles, plywood, OSB, etc., and will tend to radiate the heat they generate during those hot summer days into the cooler areas of the building easily. Installing radiant barriers and IRCCs places a low “e” surface just below (or to the underside of) the roof to retard this heat influx, redirecting it back through the roof and out of the structure. The result is drastically cooler attic spaces (5-20 degrees F or more), which increase the operating efficiency of the standard r-value insulation in the structure, resulting in reasonable savings on air conditioning bills (5-15% or more).
Every structure is different and many factors involved in the total heat flow of the system will cause every building to experience different results, however. But with a material cost of just pennies per square foot, and an installed cost of $0.50-$1.00 per square foot for IRCCs and $1.00-$2.00 per square foot for radiant barriers, the ROI can be much more rapid than other insulation technologies.
Most radiant barriers have slightly lower emissivities than IRCCs, but IRCCs like SOLEC’s LO/MIT–II MAX (e=0.147) provide a balance of high efficiency, low material cost, low installation cost, and long-term performance. LO/MIT is electrically non-conductive, moisture permeable and does not require any maintenance for the life of the roof. An average home can be treated in about a half a day and the savings will only increase as utility rates continue to climb.
So, not only are radiant barriers and IRCCs helping construction go green, they can help save some green as well.