The environment is playing havoc on our lives, and living is becoming more difficult as homes are growing warmer. Extensive use of cooling machines is adding to the woes by damaging the environment with an increased carbon footprint. Therefore, it is natural for homeowners and businesses to take measures to reduce the environmental footprint by using double glazing and improving home insulation to using LED lights and reduce the dependence on air conditioners.
The roofs are drawing a lot of attention because even small improvements in roof construction can reduce the heat load of buildings considerably. In the process, there are opportunities for reducing the carbon footprint by replacing a standard roof with green roofs comprising of lovingly cultivated plants or installing the trend-setting solar panels that can help to achieve the goal. Also, the trend of installing cool roofs is fast catching up because of the roof’s capacity to reflect sunlight instead of absorbing it. When the sunlight bounces back from the roof surface, it reduces the heat transmission through the roof significantly. It keeps the home interiors cool even when the outside temperature is very high.
The heating problem starts with the roof
According to the experts at Patriot Roofers Salt Lake, when the world is experiencing heat issues that are spiraling at a stupendous rate, all eyes are on rooftops that contribute considerably to the problem. None of the traditional roofing systems consider the heat load during roof design, and this leads to poor roof design with respect to its ability to control heat. Most roofing materials do not possess any heat reflecting property due to which the roof temperature can be higher than the air temperature by almost 90oF. The problem is especially experienced in densely populated areas that turn into ‘heat islands,’ a term coined to explain the phenomenon of an abnormal rise in temperature in homes at particular places.
In such conditions, the average air temperatures can be higher by 5.4oF than the surroundings during the day, and during the evening, it can be as higher by 22.4oF. The effective solution to the problem is to install cool roofs that can prevent the occurrences of heat islands.
The vicious heating cycle
Cool roofs have an answer for tackling the heat generated from solar rays by reflecting the major part of solar energy. During midday, when the sun is directly above our head, any flat roof receives about 1,000 watts energy from sunlight for every square meter of the roof. Larger is the roof; more is the heat generation. A traditional roof will absorb most of the energy and heat the building underneath as well as the surrounding air. Air conditioners suck in the hot air and work harder to keep the building fresh and emit more harmful gases into the environment to make it even hotter. All this will end by installing cool roofs.
The fast-growing popularity of cool roofs
Cool roofs are fast growing in popularity across the globe, and the market size that was estimated at $18.4 billion in 2018 is projected to grow at a CAGR of 5.7% until 2025. The demand for cool roofs is likely to grow fast as the push for green buildings keeps increasing, which will further propel the market growth. Rapid urbanization, together with the removal of trade barriers for foreign investments and the expansion of the global construction industry venturing into newer markets, are fueling the demand for cool roofs that belong to the roofing system of the new era.
The evolution of cool roofs
The powerful technology of cool roofing systems has emerged as a game-changer in controlling the temperature of buildings. Cool roofs prevent heat absorption by roofs by reflecting the sunlight that radiates the heat back to the atmosphere and, in the process, maintains a more controlled and comfortable indoor environment.
Cool roofing is one of the high impacting green technologies that are not as new as it appears. It began with the research by the Department of Energy in California and Tennessee to analyze solar radiation control coatings on rooftops. Simultaneously, research continued to study the effect of light-colored coatings on rooftops. The studies revealed that solar reflective roofs, as well as vegetated roofs, could lower overall temperature in urban areas.
In 2001, the technology that is in use today finally emerged in California when excessive demand for energy and inadequate power supply led to frequent power outages. To lower peak energy demands and reduce the incidents of power outages and blackouts, the idea of installing cool roofs gained momentum.
How cool are roofs
To determine how cool a roof is, you must consider the factors of solar reflectivity and thermal emittance. Solar reflectivity is a measure of how well the roof reflects sunlight and solar heat from the building measured on a 0 to 1 scale with higher values indicating cooler roofs. The most efficient cool roof can reflect more than 65% of solar energy from the building, while only a small percentage of heat passes into the building. In the case of traditional roofs, the reflective ability of solar energy ranges between 5%-15%.
The ability of a roof to release the absorbed thermal energy or heat represents the thermal emittance. In warmer areas, a higher thermal emittance helps to ensure the least retention of heat inside the building and thereby creating cool interiors. The scale for thermal emittance is the same as that of solar reflectivity from 0-1, which corresponds to 0% to 100%.
By clubbing the above radiation properties, scientists have derived the index named Solar Reflective Index or SRI that corresponds to the temperature attained by the material when exposed to the sun. The scale used for measuring SRI ranges from 0 to 100, with higher values denoting cooler roofs.
Painting the roof white by using a highly reflective paint can reflect about 85% solar heat and result in the least increase of the surrounding temperature together with a cooler home.