As the demand for energy-efficient building products increases , metal roofs are being praised for their long-term cost-cutting potential. Although solar-reflective coatings for roofs have been instrumental in reducing energy costs, a study funded by the U.S. Department of Energy and conducted by the Oak Ridge National Laboratory highlights another reason why metal roofs promote energy efficiency.
The study included field testing of an asphalt shingle roof and a stone-coated metal shake roof that had comparable thermal-emittance and solar-reflectance qualities. The asphalt shingles, however , were nailed directly to the roof deck with no air space below. The metal shake roofing was attached with a batten/counter-batten system that allowed airflow underneath. Researchers found a 45% reduction in the flow of heat with the metal roof, mostly attributable to the ventilation above the sheathing.
In cool weather conditions, direct-nailed asphalt shingle roofs result in significantly larger heat loss from attics because the air gap under a metal roof seems to offer insulating qualities that reduce heat transfer. The study also finds an up to 25% reduction in annual cooling costs because much less heat is transferred from the roof to the interior when the roof has sufficient airflow underneath.
High-performance metal roof coatings combined with a batten or counter-batten system can help reduce both operating and maintenance costs. As the demand for energy-efficient and durable building products grows , metal roof manufacturers are rising to the challenge.