The energy-efficiency building regulations that came into effect in November last year have steered the South African building industry into a more eco-friendly direction.
Ceilings, walls and windows will have to meet minimum requirements for preventing heat loss in winter and heat gain in the summer. This is partially due to the urban heat island (UHI) effect, whereby the concentration of structures and waste heat from human activity has resulted in a warmer envelope of air over urbanised areas. This not only taxes the air-conditioning units of buildings, but increases pollution and ozone levels.
Environmental studies Professor Ross McKitrick from the University of Guelph published a paper on the phenomenon, claiming that half of global warming over the last 20 years has been caused by UHI. The three main causes of global warming are said to be the reduction of urban vegetation, increased dark roads and parking surfaces and the concentration of buildings with dark roof surfaces.
Christo Pienaar, marketing director of Modek, a company which specialises in glass reinforced polyester (GRP) and polycarbonate roof sheeting, says he believes that energy-efficient roofing is a real solution to the problem. “Although increasing parks and trees in urban areas are wonderful, the demand for space in cities does not make it a viable option. It’s also not possible to replace roads or parking lots with cooler surfaces. That leaves cooler roofing as one of the simplest and most cost-effective solutions.”
He says cooler roofing systems are a process that is encouraged to lower the energy consumption of buildings and reduce urban heating. “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.” He adds that the environmental impact is quite significant. “A Lawrence Berkley National Laboratory study recently found that worldwide reflective roofing would produce a cooling effect equivalent to offsetting a reduction of 24 gigatons of CO2 emissions. Unfortunately, unlike the United States, cool roofing is not required by law or rewarded with a rebate in South Africa, and very few companies have produced such roofing products.”
According to him, one such example is the recently launched Modek Heat Stop product. It is a polycarbonate-profiled extrusion manufactured in South Africa, which has a co-extruded layer of ultraviolet-stabilised surface protection on the weather side. “Microscopic reflective particles are incorporated in the core material, which creates the silver colour and reflective quality of the product.” He explains that 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 lead to 10-30% energy savings.”
Energy savings are, of course, a huge bonus. International tests have found that a typical 4 635m2 eco-friendly roof can result in cooling savings of up to R69 650 per year as the temperature inside the building would be on average 5-7C cooler than with a dark roof. “Choose a product with high reflectance, a good warranty and a history of performance,” Pienaar advises. “It is important to consider how much reflectance a system retains over time, not just the initial reflectance.” He adds that location also plays a key role. “If winters are harsh, the energy savings in summer may be eliminated by heating expenditure in winter.”
Pienaar also advocates the use of translucent roof sheeting as a means of reducing energy costs. Polycarbonate, acrylic clear glass and most tinted options can be used to introduce direct light to a building. “A GRP roofing system can be used to introduce diffused light in industrial, commercial and sporting facilities.” He further explains that if roof lighting totals up to 15% of the floor area, energy savings increase significantly. “Whatever you choose, it’s clear that roofing is an environmental and economic tool. We are spreading the word and hope that more environmentalists and green building societies will join the campaign too,” he concludes.