Should this be the end for glass facades?

London's skyline will feature yet another tall glass building now that the reworked design for the Pinnacle has been given the green-light by planners. Known officially as 22 Bishopsgate, the landmark 278m high scheme is set to be the tallest building in the square mile and second tallest in London after The Shard. 

While its height might help distinguish this rectilinear edifice from some of the City's other tall buildings, its glass façades will not. London has a cluster of glazed office towers in and around the Square Mile, including the distinctive forms of the Gherkin and Cheesegrater. 

That glass is the predominant façade material for this landmark scheme is a disappointment. Partly because I think it shows a lack of aesthetic ambition but, more importantly, because it disregards the low carbon agenda and the need to minimise energy use. 

The thing about glass as a cladding material is that it is extremely inefficient from an energy perspective. According to David Coley, professor of Low Carbon Design at the University of Bath, each square metre of triple glazed façade will lose 10 times as much heat as a simple cavity brick wall with "a little bit of insulation".  In addition to allowing heat out, vast expanses of uninsulated glass walls also allow unwanted heat into offices, much in the same way a greenhouse is warmed.

Let me be clear: I don't have a problem with glass per se: my issue is that glass facades have become the boring old norm for tall office buildings despite leaking heat on cold winter's days and turning offices into ovens on warm, sunny days. 

And, because buildings are built to last decades, that means years of throwing heating and cooling energy at an office in order to ensure a comfortable working environment. It is a situation that will demand progressively more energy with the hotter, drier summers expected from a warming climate as the century progresses. 

The City planners described 22 Bishopsgate as exemplifying "many of the qualities we are looking for in our landmark buildings". Really? 

This statement from an organisation that published the London Climate Change Adaption Strategy; a document which includes advice on managing heat risks which states: "The City of London Corporation should ensure that new buildings are designed to provide a comfortable internal environment in the face of climate change, with the least use of energy over their lifetimes".

Some architects have acknowledged the need for change. Ken Shuttleworth, for example, was one of the team at Foster and Partners responsible for designing the glass-clad Gherkin. However, since leaving the practice in 2006 to found Make architects he has been a vocal opponent of "our love affair with transparency," calling instead for buildings to be designed to relate to their location and climate. 

Shuttleworth is right. Designers should use the façade to design out overheating problems rather than rely on energy-intensive cooling technologies. It is time for a new aesthetic. Developers, architects and tenants need to move on from the boring same-old, same-old concept of towers with energy demanding floor-to-ceiling glass facades. 

Rather than simply incorporating monolithic expanses of glazing tall towers should showcase a far more exciting, opaque façade aesthetic, one where clever design fuses energy-efficient, high-performance cladding with windows, which have been sized and positioned specifically to maximise, daylight, views and ventilation. The world is evolving, the climate is changing and so too should facade design.

Posted by Andy Pearson