London’s City Hall: a building’s shape maximizing natural solar heating

How the City Hall of London has been designed by Foster+Partners to optimize the sun impact on the building?


Description of the building

This building, home of the Greater London Authority, has been built in 2002. This project was led by the architecture office, Foster and Partners. The design of the City Hall made of glass walls is a green building thanks to the implementation of ecological technical breakthroughs. Here is a list of some green aspects of the construction: natural ventilation, groundwater cooling in summer, solar panels on the rooftop. The building is 45 meters high and includes 10 floors. The challenge taken up by this project is to consume a quarter of the average energy consumed by a building of this type.

An energy-saving shape

The sun has a huge impact in the building energy balances. To my mind, it is a really interesting goal for architects to take this into account in the design of a building. This is what it has been undertaken for the City Hall of London.

One major point of the design of this building is its envelope. Actually, the shape is derived from a geometrically modified sphere for energy-saving reasons. The design has been made to maximize the natural solar heat and minimise the negative effects of the sun. This shape has been generated by analysis to find the way to both reduce solar heat gain and energy loss via the building’s skin. This shape minimizes the surface area of the envelope of the building. There is around 25% less surface area than a cube of the same volume. This results in the optimization of the energy costs.

Another point of the shape of the building deals with the leaning of the building. The City Hall is reclined towards the south. Furthermore, south leaning floors protect the indoor building from the sun by creating shadow.


The real energy-efficiency of this building

Now, since we know more about the conception of the shape of this interesting building, I am wondering whether it is really efficient or not. Despite a design made to reduce energy consumptions, energy use measurements of 2012 are not positive, around 375 kWh/m2/year. This figure has given a rate of D in the Display Energy Performance Certificate. This is an English and Wales certification, where A is the best grade and F the worst one.

To know more about the project:


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