Clean COLORBOND™ steel with Thermatech™ solar reflectance technology coating was specified for Holdsport Ltd’s warehouse and office building in Philippi.
An eye-catching warehouse and office building in the Cape Town industrial suburb of Philippi was purpose-built for Holdsport Ltd. The building is clad with multi-coloured pre-painted steel panels and has a high solar reflective index roof to minimise inbound infrared radiation.
The popular roofing material, Clean COLORBOND™ steel with Thermatech™ solar reflectance technology coating, provides the walls and roof of the structure. According to Holdsport CEO, Kevin Hodgson, this modern facility of 11,000m² enabled the company to expand the distribution of locally sourced products in addition to the distribution of directly sourced.
The Solar Reflectance Index (SRI) is a value that incorporates both solar reflectance and thermal emittance in a single value to represent a material’s temperature in the sun. SRI quantifies how hot a surface would get relative to standard black and standard white surfaces.
Cape-based architects for the building, Bam Architecture, advised that design approval meant SANS 10400 part XA compliance for the office portion of the building. Accordingly, the energy efficient building utilises high performance glazing and cavity insulation in certain walls, as well as under the concrete roof slab. To support optimal thermal performance, the building is clad and roofed using premium brand pre-painted aluminium-zinc material, Clean COLORBOND™ steel AZ150.
The roof uses a Global Roofing Kliplok 406 profile made from Clean COLORBOND™ steel in colour African White (TCT 0.53mm) with SRI value of 85. The walls sport an IBR686 wall cladding of the same steel (TCT 0.47mm) in colours African White, Armour Grey and Shale Grey. Roofing and cladding was done by Chartwell Roofing.
According to Bam Architects, the choice of three colours was an aesthetic one, but the raised curved profiles in the sidewalls are walled with translucent sheeting in the return sections, which allow a degree of natural light to enter the warehouse.
BlueScope’s general manager, Wayne Miller, explains that Clean COLORBOND™ steel with Thermatech™ technology was recommended due to its extraordinary performance especially in hot climates and along the coastal zone.
In hot tropical climates, low thermal mass materials such as steel with light coloured roofs and walls can be used to reduce energy demand for internal cooling. For example, a light coloured Clean COLORBOND™ steel roof not only reduces the amount of solar radiation absorbed, but is also very effective at re-radiating heat. Such thermal comfort is maintained by the dirt resistance property in Clean COLORBOND™ steel. Since the addition of Thermatech™ solar reflectance technology, even darker coloured Clean COLORBOND™ steel products absorb less energy, creating the advantages of a cooler roof and a cooler building.
According to Wayne Miller, the solar reflectance technology lowers the surface temperature by absorbing less heat from the sun. “In addition, our product’s outstanding dirt resistance property ensures the roof looks newer for longer. This also assists in cooling.”
In a comparison between a Clean COLORBOND™ and a conventional steel roof, both uninsulated, the positive effect of dirt resistance technology is illustrated. Tests show that after two years’ exposure, assuming an irradiance of 1000W/m², exterior temperature of 36°C and a high thermal emittance value of 0.85, typical of pre-painted steels, the Clean COLORBOND™ steel roof’s temperature is almost 10°C cooler than the conventional steel roof and it radiates more than 40W/m² less heat down into the building.
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Advice for improving energy efficiency:
• Use light coloured roofing materials to reduce solar heat gain.
• Use low thermal mass materials that respond to temperature changes comparatively quickly in contrast with high thermal mass materials that take longer to heat or cool.
• Insulate the walls, ceilings, roofs and suspended floors.
• Favourably orientate the building and provide exterior shading to control solar heating and wind flow.
• Thermatech™ solar reflectance technology.