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Auditing, Planning, and Retrofitting
Published in Stan Harbuck, Donna Harbuck, Residential Energy Auditing and Improvement, 2021
The color of the roof affects the surface temperature. For instance, a white strip on a black surface can be 10 to 15 °F cooler than the darker areas around it. Solar reflectance also significantly influences the surface temperature of any surface. If the roof receives full sun during the cooling season, consider applying a white or reflective roof coating to help keep attics from overheating as much and greatly reduce solar gain in the home. Reflective roof coatings can cut cooling loads 10% to 60% simply by reflecting solar radiation. This is in addition to color related temperature differences. Even higher numbers are typical if the home has no attic insulation. These coatings can be applied over common roofing materials, typically last 7 to 12 years, can protect the roof from water penetration if they are elastomeric, and can extend the life of the roof. A typical cost is between $0.75 and $1.50 per square foot (not including incidental repairs) if both labor and materials are included. Check actual local prices to make sure of cost-effectiveness. The solar reflectance values for several types of roofing are listed in Table 7-5.
Maintaining Commercial Roofs
Published in Ryan Cruzan, Manager’s Guide to Preventive Building Maintenance, 2020
Built-up roofs can also have a silvery, shiny aluminum based top coat applied. This coating reflects sunlight and helps to keep roof temperatures from becoming excessively high. This type of roof coating needs to be re-applied roughly every five years.
Accelerated biological ageing of solar reflective and aesthetically relevant building materials
Published in Advances in Building Energy Research, 2019
Giulia Santunione, Chiara Ferrari, Cristina Siligardi, Alberto Muscio, Elisabetta Sgarbi
Studying microbial growth under natural conditions is too slow as an investigation approach for development and improvement of industrial products. Several studies have been carried out on surface bio-ageing with the aim of analysing and assessing the energy impact on the buildings (Cheng et al., 2011; Cheng et al., 2012; Gaylarde & Gaylarde, 2005; Kultur & Turkeri, 2012; Mastrapostoli et al., 2016; Pisello, Castaldo, Pignatta, Cotana, & Santamouris, 2016). The microbiological analysis shows high bacterial and fungi load of the aged cool roofs compared to the reference sample of a new material (Mastrapostoli et al., 2016). It has been shown through simulations that the application of a new cool roof coating can decrease the energy demand for cooling by 72% compared to the aged cool roof. On the other hand, natural ageing takes up to three years of surface exposition to the weather conditions. Moreover, natural ageing, and particularly bio-ageing, are characterized by a low repeatability; this is due to the wide variability of environmental conditions and mainly by geographical position of the building. Developing a laboratory approach to biological ageing may thus provide a reproducible and reliable test method to assess the long-term performance of building materials, considering changes in solar reflectance and emittance over time (Kultur & Turkeri, 2012). In fact, with artificial ageing, what in nature occurs after several years can be compressed in a very short time (months), by forcing the growth of microorganisms through a strict control on different environmental conditions (Ferrari et al., 2015). Accelerated biological ageing can certainly be faster than natural processes and also repeatable, two fundamental requirements of industrial research and development.