The energy-efficiency regulations for buildings, which came into effect in November last year, have steered the South African building industry in a more eco-friendly direction. One issue that has been raised in this context is the urban heat island (UHI) effect, which occurs as a result of a concentration of buildings, hot surfaces and waste heat from human activity that creates a warmer envelope of air over urbanised areas. This not only taxes the air-conditioning systems in buildings, but also increases pollution levels significantly.
Christo Pienaar, marketing director of Modek, a company which specialises in glass reinforced polyester (GRP) and polycarbonate roof sheeting, says that cool roofing is a real solution to the problem. “Cool roofing is one of the simplest and most cost-effective solutions to diminish the UHI effect and it supports energy efficiency in buildings.”
Pienaar says that with cooler roofing systems the roof reflects the sun’s heat and emits absorbed radiation back into the atmosphere, keeping the building at a cooler and more constant temperature. The environmental impact is quite significant.
“A Lawrence Berkeley National Laboratory study recently found that if reflective roofing were used worldwide it would produce a cooling effect equivalent to a reduction of 24 gigatons of CO2 emissions,” he says. “However, in South Africa, unlike in the United States, cool roofing is not required by law nor rewarded with a rebate, and only a few companies produce cool roofing products.”
According to Pienaar, the recently launched Modek Heat Stop can be considered a cool roofing product. Manufactured in South Africa, it is a polycarbonate profiled extrusion which has a co-extruded layer of ultraviolet-stabilised surface protection on the weather side. “Microscopic reflective particles are incorporated in the core material, creating the silver colour and reflective quality of the product,” he explains.
“It is a step in the right direction. The product eliminates about 60% of the sun’s radiated heat and reduces the cooling load of the building, which in turn reduces the use of air-conditioning and can lead to energy savings of between 10 and 30%.”
International tests have reportedly found that eco-friendly cool roofing can reduce internal temperatures by 5 to 7°C on average, compared to internal temperatures under a dark roof, and in turn deliver substantial annual energy savings by limiting mechanical cooling requirements.
Pienaar also advocates the use of translucent roof sheeting and skylights as a means of reducing energy costs. He says polycarbonate, acrylic clear glass and most tinted options can be used to introduce direct light into a building and a GRP roofing system can be used to introduce diffused light into a building. These products are often used in industrial, commercial and sports facilities. Pienaar adds that if rooflights total up to 15% of the floor area, energy savings increase significantly.
“Whatever you choose, it’s clear that roofing can be used as an environmental and economic tool,” Pienaar concludes.
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