Innovative steel usage in warehouse
A recently completed warehouse and
office in Philippi, Cape Town, is clad
with multi-coloured pre-painted steel
panels and has a high solar reflective
index roof to minimise inbound
infrared radiation. Popular roofing
material, Clean COLORBOND™ steel
with Thermatech™ solar reflectance
technology coating, was recently used
in the construction of this high tech
new warehouse for client, Holdsport
Ltd.
The Solar Reflectance Index (SRI) is
widely used by green building rating
tools to mitigate the Urban Heat
Island (UHI) effect. 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. 75mm
Factorylite insulation was used under
the roof. To support optimal thermal
performance, the building is clad and
roofed using premium brand prepainted aluminium-zinc material, Clean
COLORBOND™ steel to specification
AZ150.
The sparkling white roof was built
using Global Roofing’s Kliplok 406
profile made from Clean COLORBOND™
12
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 0.47 mm) in
colours African White, Armour Grey
and Shale Grey. Roofing and cladding
was by Chartwell Roofing. According
to Bam Architects, the choice of 3
colours was an aesthetic one, but the
raised curved profiles in the sidewalls
(see photograph) 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.
According to Miller,
the solar reflectance
technology lowers
the surface
temperature by
africandesignmagazine.com
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.”
In a comparison between a Clean
COLORBOND an d 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 COLORBONDTM steel roof’s
temperature is almost 10° cooler
than the conventional steel roof and it
radiates more than 40W/m² less heat
down into the building. AD
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The Holdsport Building’s SRI side cladding