Energy Efficient Roofing: Metal

In 2004 the Oak Ridge National Laboratory concluded a three-year study of metal roofing materials; this study evaluated the energy efficiency as well as the service life of various metal roofing materials. These materials included painted and unpainted galvanized steel, painted and unpainted Galvalume®-coated steel, and painted polyvinylidene fluoride (PVDF) aluminum, and were tested on both steep and low slope installations.

This study showed that both painted and unpainted metal panels maintain their energy efficiency better than any other roofing system studied. Pre-painted metal roofing retains ninety-five percent of its initial solar reflectance over a three-year period. Some field data showed that PVDF painted metals maintained a resistance to soiling for at least thirty-five years! Infrared emittance increases over time, but the study shows that it isn’t in any way affected by the climate because of the overall uniformity of the increase.

A basic, unpainted metal roof will reflect much of the solar radiation that is usually absorbed into the attic and home by the traditional asphalt roofs. Pre-painted or granular-coated metal roofs will even go a step further and cool the home by re-emitting much of what solar radiation is absorbed. This is definitely a good choice for warmer climate homes.

By installing a metal roof you could cut your summer cooling costs by forty percent! If the roof is a highly emissive metal roof it could even reduce the urban air temperature by as much as twelve degrees Fahrenheit! Metal roofs sure seem like an energy smart idea.

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