Solar shading: how we have evolved from extruded aluminium fins
Posted on Fri, Jan 13, 2012
It doesn’t seem like that long ago that a static 12” (30cm) blade, pitched at 12” and angled at 45 degrees, was your archetypal external shading array. With advances in architecture, glazing and curtain walling, in retrospect it seems absurd to design a building with large expanses of glass and then shroud it in metal. Yes, solar heat gain was an issue, but only a few companies were interested in exploring how they could develop shading to compliment the design and assist with the internal comfort in temperature and natural light.
Moving on to bigger blades, longer spans
With time, some companies realised they could offer architects the ability to span further, minimising fixings and penetrations back to the structure, to use bigger and less frequent blades and to go vertical. Traditional 12” (300mm) blades were developed to span 10’ (3m), and in some cases companies went to the extreme of extruding giant 27½” (700mm) blades that could span 30’ (9m), but at huge weight (14lbs/6.4 kg per foot) and cost.
Losing weight, gaining visibility with perforated blades
Perforated sheet blades swiftly moved to replace the traditional aerofoil. Lighter construction, single sided perforated sheet aluminium was either folded around a central core or clad over a skeletal frame. This provided the architect with the larger spans they were after together with lower costs and better visibility. A comprehensive level of heat gain control could be achieved by using perforated sheet material with an openness factor of maybe 25%. But this also had the added advantage of increasing outward vision, so that the occupants no longer felt that they were stuck behind a solid metal wall.
Moving with the sun
Only a handful of companies realised that, with the changes in solar altitude and azimuth, a fixed system was a huge compromise. The need for solar shading in the hottest months meant that to provide good shading at peak time, visibility outwards and natural light into the building would be at risk. The solution was to design automated systems, which quickly gained ground. These systems moved the blades incrementally to follow the sun, providing the best level of shading. Most importantly, they opened the blades when there was no direct radiation, allow as much natural light as possible into the building.
Optimising performance, cutting costs with intelligent design
The companies with the most experience quickly realised that with intelligent design, the use of efficient motors, factory and unitized assembly meant that installation, running and maintenance costs were much closer to the static equivalents than most specifiers thought. This signalled yet another move away from fixed extruded blades.
Over the next 3 blogs, we will look further at how things have moved on, from savings that can be made from shading to Net Zero Energy Controls. In the next blog we will look at the benefits of glass shading, and how it can provide outward vision and reduce solar heat gain.
Associated blogs:
Martin Read is responsible for Solar Shading for Colt North America, with over 15 years experience in static and automated, aluminium, glass and BIPV shading.
