A recent study by Urban Green Council examined the dangers of all-glass high rises in a blackout. These buildings are heavily reliant on space conditioning to provide comfortable and safe indoor environments. Without electricity, systems would cease to function and summer interior temperatures could rise over 100F over the course of a few days.
The culprit is the exterior skin of the building – glass is extremely conductive. The best curtainwall assemblies typically achieve R-values around R4. A typical opaque wall built to code standards can easily achieve R20 or higher. This does not account for the radiant heat transfer through the glass which further reduces the performance of glazed walls. This effect is typically measured by the glazing’s solar heat gain coefficient (SHGC).
The study created models of various types of existing New York buildings, and examined what would happen if there were a blackout during the warmest and coldest weeks within six months of Sandy in October 2012…
…The study found that if a similar blackout happened during a summer heat wave, the effect would be more severe: Interior temperatures could rise to more than 90 degrees the first day in a glass-walled building. After seven days, temperatures might peak at more than 102 degrees in the afternoon.
There are many in the building performance industry who question whether all-glass buildings can be considered green or sustainable. For further reading on this topic see this Building Science Corporation article by John Straube.