1. Naturally Cool Roofs: By using white vinyl or other white surface materials, a building’s albedo (ability to reflect light) can increase to 60 percent, compared to 10-20 percent on a traditional asphalt roof. This reduces heat absorption and cools the building’s interior.
2. Coated Roofs: Buildings with traditional roofs can receive a solar reflective coating that helps reflect sunlight. Once retrofitted, these roofs function the same way as naturally cool roofs.
3. Insulated Cool Roofs: A roofing system that pairs thermally resistant insulation (insulation with a high R-value) with a white or reflective roof coating makes an effective thermal barrier, keeping heat out on hot days and in on cold days. This enables building HVAC systems to work more efficiently. If U.S. commercial roofs were upgraded with high R-value insulation, annual energy savings would be estimated to exceed $2 billion.
4. Green (vegetated) Roofs: Some roofs can be covered with plant life if designed or retrofitted to handle the additional weight. Such roofs range from extensive (soil depth of 2-3 inches) to intensive (6 inches or deeper) and work with hundreds of different species of plants. Though green roofs reflect less sunlight, they provide other aesthetic and environmental benefits, including reduced storm water run-off and cleaner air.