The Benefits of a Cool Roof
The benefits of a cool roof are many. Cooler roofs reduce cooling loads resulting in a lower monthly energy bill. With a reduced energy requirement, less fossil fuel is burned to produce energy. Cooler roof surfaces also reduce the ambient air temperature, reducing the heat island effect experienced by many urban areas.
The heat island effect is a documented phenomenon where the average temperature in an urban area is higher than the surrounding countryside; once again causing increased cooling requirements, increased fossil fuel consumption, and smog. In an effort to reduce peak energy demands, many municipalities and a few states are also offering owners incentives to utilize reflective roof surfaces.
After all that, what’s not to like? In most cases, nothing. Reflective roof surfaces create an environment that is easier to cool and also extend the serviceable life of your roof. However, the benefits of adding a reflective roof system will not be realized unless these necessary initial steps are taken.
1. Visual Inspection. The roof’s surface is almost always inspected for imperfections, weak areas and failures. What is often overlooked is an inspection from below — from both outside and in. A visual inspection of the structural deck will provide valuable information as to the condition and structural capacity of the decking. If there is any doubt, a structural engineer should be consulted. Likewise, the exterior of the building should be viewed from the ground. Missing or damaged masonry, parapet caps or flashing could indicate a problem that requires remediation prior to the roof’s restoration.
2. Condition Assessment.Sometimes a simple inspection and spot repairs are not adequate to evaluate and improve the roof’s condition. If this is the case, a more comprehensive analysis may be required to fully evaluate the roof assembly’s condition. This important step should include a moisture survey to identify and measure the amount of moisture in the roof assembly. A laboratory core analysis should be completed to determine the construction assembly and condition of the existing system. Testing for asbestos-containing materials should also be done. When the existing roof system has failed or is in poor shape — multiple leaks, flashing splits, structural deck deterioration, etc. — nothing, including a reflective roof coating, can save it. Installing something over a failed roof can be compared to applying a bandage over a cancerous tumor. Maybe you cannot see the problem anymore, but the root cause of failure has not been remedied, and the problem(s) will remain and worsen. While a reflective roof can be installed over most types of roofing materials, insuring compatibility of the proposed cool roof system with the existing roof substrate should also be done here.
3. System Selection. “Cool roofs” come in many formulations and careful consideration must be given to the specific conditions that exist on the roof. For example, if the roof has daily foot traffic or is in a hail-prone area, a system with impact and abrasion resistance such as a direct-bond polyurethane coating may be the best selection in terms of performance, serviceability and life-cycle cost. Additionally, if ponding water is likely, use a system that has proven to perform under such conditions. If the roof has positive slope and virtually no foot traffic, but requires resistance to ultra-violet degradation, perhaps a silicone coating over a polyurethane foam roof is appropriate, as may be a white single-ply membrane. The key is careful evaluation of the verifiable performance characteristics of the proposed system(s) and the manufacturer. Information is typically available through the Internet, roof system manufacturers, and their licensed applicators.
4. Repair and Reinforcement. All identified weak areas of the roof should be repaired utilizing the manufacturer’s published methods and best practice. Included in this process step would be flashing repair and reinforcement, removal and replacement of wet roof areas, and the repair of any surface defects.
While there are many benefits to installing a cool roofing system, it remains important that proper steps of inspection and condition assessment be completed prior to the recommendation and installation of the cool roofing system. After the system has been installed, the owner is well advised to implement a preventive maintenance program that includes semi-annual inspections, debris removal and periodic rinsing of the surface to help maintain the roof’s reflectivity. Periodic roof maintenance will add years to the service life of the roof by identifying minor imperfections before they become major problems, and providing increased protection of the building. While the full benefit of a maintenance program will be realized with a new roof installation, a maintenance program can be initiated at any time and will extend the roof’s service life.