A white roof features a highly reflective coating or membrane with a solar reflectance value of 0.65 or higher, reflecting 65-90 percent of incoming solar radiation back into the atmosphere. This passive cooling strategy reduces roof surface temperatures by 30-40°C compared to dark roofs, significantly decreasing building cooling loads and energy consumption.
Technical Specifications
White roofs typically achieve Solar Reflectance Index (SRI) values of 65-100, meeting ENERGY STAR standards. Cool roof coatings use titanium dioxide or ceramic microspheres to maintain reflectivity of 0.70-0.90 for 10-15 years. The coating thickness ranges from 0.5-2 mm depending on the product.
Energy and Cost Implications
White roofs can reduce cooling energy consumption by 20-30 percent in warm climates. Annual savings typically range from $0.50-1.50 per square meter. Initial installation costs are $3-8 per square meter. White roofs contribute to urban heat island mitigation and are particularly effective in buildings with high roof-to-wall ratios or minimal shade.