'Walkie Talkie' building on the right of London skyline

+ Reflected solar heat from buildings can have serious consequences yet little is known about the problem.

It’s not a good day when your building is blamed for melting parts of a car. Reflected solar heat from concave surfaces has recently put some buildings in the headlines for all the wrong reasons, and I think it’s time engineers and architects had industry guidelines on this phenomenon.

Smoothly curved facades are in fashion and advanced manufacturing technology has made it easier to fabricate curved shapes in glass and metals. So there is now more potential for heat reflection problems. And amendments to designs, or worse to completed structures, can be very expensive – not to mention the reputational risk involved.

Yet currently little is known about the problem. For one thing, clients understandably prefer to avoid publicity. High-profile examples include the ‘Walkie Talkie’ building at 20 Fenchurch Street in London, the Walt Disney Concert Hall in Los Angeles and the Vdara Hotel in Las Vegas. But there are probably more that we don’t know about.

Another issue is the limited body of publicly available knowledge. The problem of reflected heat is difficult to analyse accurately and requires highly specialised analytical tools and very detailed knowledge of the characteristics of the surface causing the reflections. It is only in the last year or so that Arup has developed the capability to model this.

All this means there are currently no widely accepted criteria or guidelines on allowable heat reflection intensity. The legal quagmire that results from these problems produces a situation where no one raises their head above the parapet to even develop guidance for engineers and architects.

Is there anything we can do in the meantime without such guidance? Prevention is obviously preferable to cure but there are still things that can be done if problems are found late in the design or construction process. One way of addressing this would be with matte façade finish which would significantly reduce the strength of reflection, or you could adjust the shape of the façade so that strong, focused reflections do not occur. 

Another option would be to use shading screens to prevent sunlight from reaching the façade in the first place or shading to block the reflections. You might even have to physically prevent people from accessing areas liable to strong reflection.

None of these options are as good as designing from the outset with proper guidelines for reflected solar heat. These are what we urgently need now.