23 June 2012

A cool roof for Blue Route Mall upgrade

Clean COLORBOND™ ULTRA steel, a white pre-painted AZ200 roofing material manufactured by BlueScope Steel, was recently used in the extension and upgrading of the Blue Route Mall, a popular shopping destination in Tokai, Cape Town. 

The steel was formed into Ziptech 420 by Hulamin for the main roof and into Ziptech XT cladding and Cladtech F350 panels for the ceilings. The product was used in all the new sections of the mall that were built during the refit – with the new roof area totalling about 30 000m². 

To enhance a project's rating under the Green Star SA system, or simply to promote sustainable building practice in refit projects, BlueScope Steel – a member of the Green Building Council of South Africa (GBCSA) – recommends that roofing systems should optimise a building’s levels of performance and lifespan in addition to minimising its carbon footprint. 

BlueScope Steel defines sustainability in roofing as roofing that:

-       provides a long service life and is ultimately recyclable;

-       dematerialises the substrate and the coating to achieve a lower coating mass but providing better performance;

-       reflects the maximum amount of incoming solar radiation by using an advanced infrared coating system. 

Wayne Miller, head of operations for BlueScope Steel in Southern Africa, says, “The white colour chosen by the designers of the Blue Route Mall upgrade provides an ideal cool roof. The unique paint system used on all colours of the Clean Colorbond™ steel range incorporates a number of essential sustainability features such as high reflection of incoming solar radiation (SRI), exceptional colour retention, anti-chalking and dirt resistance.” 

According to Lance Wilson of Hulamin, Clean Colorbond Ultra steel was specified for its “cost-effective corrosion resistance, the durability of the substrate and superior coating”. The project architects were Louis Karol and the roofing contractor was. 

Under harsh climatic conditions and especially within the five-kilometre coastal zone, Miller advises that “only premium grades of alloy-coated steel such as ZINCALUME® and pre-painted steel such as Clean Colorbond should be used. These roofing products are all manufactured with a 55% aluminium, 43.5% zinc and 1.5% silicon coating (AZ150 coating). The same products can be used under normal circumstances to gain much longer service life.” 

This advice is based on years of experience with roofing in the aggressive climatic conditions of Southeast Asia and Australia. ”If you are building in severe industrial environments where there are aggressive fumes or particulate fallout within a 200-metre radius, or if the location is within 200 to 400 metres of the sea, we would advise using our Clean Colorbond Ultra. This has an AZ200 coating – coated to a mass of 200 grams per square metre over the steel substrate. 

“Correctly applied, our product should give a lifespan up to four times longer than the standard pre-painted galvanised steel”, Miller says. He highlights, however, that it is important for the project manager or designer to contact the BlueScope Steel office before installing the roof because the warranty of performance is subject to terms and conditions.