What's behind the Walkie Talkie 'death ray'?
Tom Bassett explains the Walkie Talkie’s ‘death ray’ phenomenon
Glossy images and dramatic stories of singed carpets, blistered bicycle seats, and buckled Jaguars have got the nation talking wildly about a block of steel and glass in the City.
‘Walkie Scorchie’ is our new love-to-hate monument of architectural ignorance, with phrases such as ‘London’s death ray’ now being coined.
‘How could he make the same mistake twice?’ is the question on everyone’s lips as Viñoly has been outed as the architect whose Las Vegas hotel caused the same issue in the City of Sin years ago.
By his team’s calculations, they underestimated the intensity of the sun’s beam on Eastcheap by 50 per cent. So what, exactly, is going on?
The critical issue here is the stretch of Eastcheap which is the recipient of the focussed reflected beam never sees the sun directly, except for near sunrise and sunset around midsummer. These buildings face north – a section of the sky the sun occupies only at low altitudes in the summertime – and they face 5 to 6 storey buildings which block the sun’s light from low altitudes. For 99 per cent of the year, these properties never receive direct sunlight, and only then with weak intensity.
So you can imagine: all day long in the summertime, the barbershop’s carpet and the café’s tiled exterior are warmed only by the ambient temperature of the air. Suddenly, on a clear late summer’s day in 2013, they are superheated by a visiting blast of intense focussed light. The molecules of the materials go into overdrive and - in the case of the carpet - combust; in the case of the tiles, the stone superheats, the bond with the cement takes the toll, and they pop out of position. If the tiles had received a daily dose of direct sun and subsequently cycled through some healthy diurnal expansion and contraction, the superheating most likely would not have resulted in what we’ve been seeing in images.
Likewise, the heat is only the result of direct light– the building is too far away to emit damaging infrared heat. Light is absorbed or reflected depending on the colour of the material it hits, which is how we know an apple is red and a Jaguar is black. White reflects 95 per cent of all light, and black absorbs almost all light. This, too, is critical: if the Jaguar had been white, deformation of the panelling most likely would not have occurred. Likewise of the tiling and the bicycle seat. Think of romantic images of villages in Greece with their whitewashed buildings – these are painted out of the same reasoning. White reflects the sun’s light, and therefore the heat. It’s a potentially expensive experiment, but park a white car and a black car in the now restricted bays on Eastcheap, and watch what happens.
Furthermore, and in defense of Viñoly, modelling this type of reflection is notoriously difficult. First of all, the model of the Walkie Talkie would have to be mathematically perfect. This isn’t too difficult of an issue nowadays, but for instance our research department uses SketchUp and Google Earth as sources of urban models. The models publicly available from these resources are currently drawn from images and not directly from designers themselves. The model seen on Google Earth of the Walkie Talkie building, for instance, has a triangulated face, and thus does not reflect modelled sunlight identically to the
as-built building. A better model is required, and, due to the complexities of the geometries of the building, this would really only be available directly from the architect.
Secondly, solar intensity is generally supplied in hourly increments, which makes it hard to calculate what happens minute by minute. Now don’t get me wrong, building physicists and modellers can extrapolate this solar data into minutes, but, regardless, the data is averaged according to what is known as a ‘typical year.’ Data for a ‘typical year’ is an average of all the previous 30 years, so whilst the weather data is useful for drawing likely assumptions based on what the day has been like over the past 30 years, it will never be accurate for what happens on a specific day. Thus, in the case of this crazy week in September, no modelling based on available weather data could ever predict exactlythe ‘temperature’ of the solar beam. Which is why Viñoly’s predictions were only half of what actually occurred last week.
Thirdly, the intensity of light is down to the angles of incidence. The more directly the sun strikes a surface, the greater the intensity, which is why we lie down to sunbathe during the day, and why baboons in Africa stand up and raise their arms toward the rising sun to warm up in the morning. You’ll notice the fried egg was being held almost perpendicular to the sun’s rays, receiving the maximum intensity. The panels on the Jaguar, too, were almost perpendicular to the reflected beam. Had the barber’s carpet been at a similar angle, the damage would have been worse. This angle will play a significant role as decisions are made as to how best disperse the beam.
Which brings me to this point: a permanent fixture on Eastcheap isn’t the answer to the unfortunately monikered ‘death ray,’ as the sun will only rear its head for a few sunny days in late April/early May and again in early September.
Likewise, the architect shouldn’t be harnessed with paying millions to alter the design at this late stage. Instead, the affected occupants of Eastcheap, until recently living in the shade and coveting their sun-filled neighbours across the street, should welcome this visit and highlight it with temporary street art and an ad-hoc festival of all things solar. I’d say they’ve never seen so much business as these last few days, and you can certainly count me in to cue up next spring for a carbon-neutral egg and bacon butty.
- Tom Bassett is a building physicist at the Welsh School of Architecture