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Although tiled roofs are the norm for existing houses in most countries across Europe, metal roofs could replace conventional roof construction for many new-build and refurbishment projects. A metal roof could offer advantages in installed cost as well as the potential for reduction in cooling loads, particularly if solar reflective coatings are used. The main barriers to their use are resistance to unfamiliar construction techniques and planning restrictions, particularly relating to traditional building typologies.
This paper compares the thermal performance of tiled and metal roofs in different climatic conditions in Europe, in order to gauge whether metal roofs present any advantages over tiled roofs with regard to reducing the need for cooling during hot periods, and thus reducing the energy use and emissions of CO2. There is evidence from Florida in the US that this could be the case.
In a study of seven houses constructed in 2000 with different roof finishes, a reflective white colored metal roof was calculated to save 39.7% cooling energy during three weeks in July 2000 compared with the control home with standard dark shingles (Parker et al., 2002). In another study in Florida, Parker et al. (1998) compared 11 residences featuring different roof colors and, on the basis of these experimental results, developed a model that estimated the impact of reflective roofing in 14 different climatic locations around the United States. The conclusions were that a reflective roof finish resulted in annual cooling savings ranging from 13% to 58%, whilst heating requirements were increased by 3% to 6%. The advantage in overall energy savings of using light colored roofing was the greatest in lower latitudes, though increasing roof insulation was found to be more effective in the colder climates further north.
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