Sustainable Roofing: Hospitality – Hotel Verde

by Tania Wannenburg

Two case studies show the aptness of Clean COLORBOND™ steel with Thermatech™ solar reflectance technology coating for both new builds and refurbishments.

Solar Reflectance technology of steel roof material proven

Popular roofing material, Clean COLORBOND™ steel with Thermatech™ solar reflectance technology coating, has proven its proficiency for both new builds and refurbishments. Two case studies, in the hospitality industry and a major convention centre respectively, demonstrate the aptness of this material for any sustainable building.

Hotel Verde – a sustainable landmark
Clean COLORBOND™ steel was specified for the construction of one of the most sustainable hotels in the world, the Hotel Verde near Cape Town International Airport. It was the first hotel in Africa and the first South African building to achieve a platinum certification across all categories of LEED Platinum Design and Construction Certification.

According to the engineer and lead sustainability consultant on the project, André Harms of Ecolution Consulting, the hotel boasts a high Solar Reflectance Index (SRI) roof which contributes greatly to its very low heating and cooling energy usage.

“We had the opportunity to change the status quo there and looked at different ways of doing everything, right from the word go,” states Harms, a trained electro-mechanical engineer who provided the expertise behind many of the high-tech aspects of the building, collaborating closely with the project architects, Heinrich Gerstner Harding Architects.

The crowning glory of the Hotel Verde, its roof, consists of 1 510m2 of exposed sheet metal roofing plus a further 255m2 which is covered by PV panels. The roofing material is Clean COLORBOND™ Ultra steel with Thermatech™ solar reflectance technology coating to specification AZ200 (TCT 0,53mm) and colour Enduring White. The Solar Reflectance Index (SRI) is 85, making this one of the coolest operating roofing materials available, complimented by an outstanding dirt resistance property which ensures the roof stays cooler for longer. The roof was installed in profile Brownbuilt Klip-Lok 406 by the roofing contractor, Scheltema.

The SRI value is widely used by green building rating tools to mitigate the Urban Heat Island (UHI) effect. It incorporates both solar reflectance and thermal emittance to represent a material’s temperature in the sun and quantifies how hot a surface would get relative to standard black and standard white surfaces. 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.

According to Wayne Miller, general manager of BlueScope in Southern Africa, the solar reflectance technology found in Clean COLORBOND™ steel lowers the surface temperature by absorbing less heat from the sun.

“Thermatech™ optimises the thermal performance of every colour in the standard Clean COLORBOND™ steel and Clean COLORBOND™ Ultra steel palettes, without changing their appearance. This provides greater thermal comfort all year round whilst using less energy for air-conditioning and hence mitigating the UHI effect,” he says. “In addition, the product’s outstanding dirt resistance property ensures the roof looks newer for longer. This also assists in cooling.”

In a comparison between a Clean COLORBONDTM 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 1 000W/m², an exterior temperature of 36°C and a high thermal emittance value of 0,86, typical of pre-painted steels, the Clean COLORBONDTM 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. This is a considerable easing of the HVAC load for any building, regardless of size.

Cape Town International Convention Centre
Clean COLORBOND™ steel provides architects with a quality pre-painted steel roofing material which offers a high resistance to the paint breakdown and corrosion typical of the extreme African climate.

Suitable for use in humid, windy and salt-laden marine environments, the remarkable performance of the Cape Town International Convention Centre (CTICC) roof is an excellent showcase for the product. A recent inspection shows that the brilliant white COLORBOND® steel installed more than 12 years ago remains largely unfaded and reflects a substantial quantity of inbound sunlight.

According to Wayne Miller of BlueScope, “Clean COLORBOND™ steel is making a major contribution to the style, performance and longevity of roofs in South Africa, and will give up to four times greater corrosion performance in the same environment than what pre-painted galvanised (Z275) material would.”

Bluescope Steel Southern Africa (Pty) Ltd
Tel: 021 442 5420
Email: wayne.miller@bluescope.com
Website: www.bluescope.co.za

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