Cool Roof Systems
Cool Roof Systems
Over the past few decades, rooftops have become a large contributor to excessive heat issues. As many as 90% of roofs in the United States are poorly designed and built with dark, non-reflective, heat-absorbing materials. Because of this, rooftop temperatures can rise up to 90 degrees above the prevailing air temperature. One area where this situation is commonly seen is in dense, populated areas such as cities, which have adopted the term “heat islands” due to their drastic temperature increases. Research states that average city air temperatures can be up to 5.4°F warmer than their surroundings during the day and up to an alarming 22°F warmer during the evenings! In light of this, cool roofing is one of the main strategies used to prevent future occurrences of heat island effects. Cool roofing is an emergent and powerful technology used for temperature control of buildings. A cool roof system prevents heat absorption by reflecting the sun’s heat and then emitting its radiation back into the atmosphere. By doing this, cool roofs allow for a more energy efficient, comfortable and controlled indoor environment.
Benefits of Cool Roof System
Costs are one of the major benefits of cool roofs. Cool roofing is known to be very affordable overall, with energy savings ranging from 7%-15% of total cooling costs. Like all roofing projects, however, costs can vary depending on multiple factors: project size, project location, climate, and ease of roof access. Some projects have very low installation costs with little to no maintenance, while the associated energy savings provide a great incentive for consumers.
Other benefits of cool roofs are:
Lower Temperatures: During hot months, internal building temperatures are much lower than those in buildings that use traditional cooling techniques.
Reduced Maintenance Costs: Many cool roofing types require little to no maintenance. Also, cool roofs typically have a longer lifespan than conventional roofing systems, lowering overall maintenance costs and extending roof life.
Reduced Energy Use and Cost: Since less air conditioning is needed during hot summer months, energy bills are lowered. One study estimates that buildings with cool roofs use up to 40% less cooling energy than buildings with dark-colored roofs.
Mitigated Heat Island Index: Less heat will be maintained during the day in dense urban areas. Not only will the overall building temperature be lower, but the surrounding ambient temperature within the urban area will decrease as well. (link-https://www.epa.gov/heat-islands)
Reduced Air Pollutant Emissions: Since air conditioning units will be used less frequently, the subsequent decrease in energy demand will result in reduced burning of fossil fuels and, therefore, reduced emissions (including NOx) and greenhouse gases (such as CO2).
Improved Air Quality: Reduced emissions and improved air quality go hand-in-hand. With fewer pollutants being emitted into the atmosphere, overall air quality will improve. Smog, which is produced by ground-level ozone, sulfur dioxide, nitrogen dioxide, and carbon monoxide, can be significantly lowered in urban areas and provide healthier breathing conditions for the population.
Utility Rebates: There are multiple incentives for sustainable efforts and many pertain solely to cool roofing strategies. Ask your Enertech representative about rebates in your area.
Types of Cool Roofs
When considering the industrial and commercial sectors, no two buildings are the same. As a result, there are multiple types of cool roofs designed to suit various building designs and structural components. Different techniques are used for low-sloped and steep-sloped roofs.
Low-Sloped Roofs have an extremely flat roof line with a slight incline for draining needs. These types are typically found associated with industrial, institutional, and commercial buildings and are great candidates for cool roofs because of their usual large roof surface areas. Since the roof is the main source of heat entry into a building, a cool one can significantly help lower heat gain and energy costs. For low-sloped roofs, cool roof techniques generally include, but are not limited to, built-up roofing, coatings, and single-ply membranes (as described below).
Steep-Sloped Roofs have an inclined roof line and are generally seen in residential settings. Materials for steep-sloped cool roofs include asphalt shingles, metal roofing, tiles, and shakes. Different cool roofing techniques are used for steep-sloped roofs because of their different structure and materials. Applying coatings over existing shingles can prevent them from drying, causing water damage. Also, since steep-sloped roofs generally account for 40% of the exterior visual appearance of a building, more aesthetically pleasing techniques (such as shingling and tiling) are therefore used to cool them.
Cool Roofing Material Options
Reflective Asphalt Shingles are composed of asphalt mats made from fiberglass. They are widely used on Steep-Sloped Roofs.
Metal roofs, one of the most popular roofing materials used today, can achieve a solar reflectance of over 70%, allowing buildings to remain much cooler and lowering their energy costs. Metal is also extremely durable and weather-resistant, lightweight, and 100% recyclable at the end of its useful life.
Cool Roof Reflective Coatings
White roof coatings are opaque and reflective, consisting of polymeric materials and some types of white pigment. They normally reflect 70% to 80% of the sun’s energy and, the thicker the layers of coating, the more reflective they are. They keep surface temperatures very close to ambient temperatures.
Reflective Single-Ply EPDM Membranes are made from synthetic rubber, or synthetic polymers such as polyvinyl chloride. These membranes are constructed to be strong, flexible, and waterproof. The top layer can be covered with pigment that increases solar reflectance. Single-Ply EPDM (Ethylene Propylene Diene Monomer) which alone accounts for 40% of the commercial low-sloped roofing market today. Its popularity comes from its flexibility among multiple climates.
Reflective Single-Ply Thermoplastic Membranes are flexible sheets made of plastic polymers. When heat is applied to this material, thermoplastics mold together and become seamless. Common examples include polyvinyl chloride (PVC) and thermoplastic polyolefin (TPO). Both PVC and TPO are among the fastest-growing roofing systems today. These thermoplastic single-ply membranes combine both the durability of EPDM membranes and the performance of a welded roofing system to provide a high-quality cool roof.
Reflective Tiles are commonly seen in warmer climates because of their high solar reflectivity. Clay tiles are a popular cool roofing material, with an SRI of over 50% and a thermal emittance of up to 86%. They are known to be extremely durable and 100% recyclable at their end-of-life use. Colors vary as well to provide a great number of options to consumers. Highly durable concrete tiles are also popular and offered in a wide variety of colors, with the ability to perform in extreme weather conditions.