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A typical ‘double skin’
building basically just adds double glazing to the exterior wall.
Such facades provide solar heating, cooling and ventilating in a variety of ways, like Trombe 
walls or greenhouse windows. Heat rises due to the thermal stack effect and air movement 
between the skins. This sucks interior air out of the building and expels it through exterior 
dampers. External and internal heat loads from office equipment or machinery may require 
extra high solar stacks. Extraction fans can be powered by solar-powered fans or wind turbines 
(or mechanical support in extreme conditions). Double skins can also warm the building by 
trapping warm air between inner and outer skins by closing dampers. The space between the 
two skins can have louvers which, if close to the outer glass skin, can reduce heat gain by 50 
per cent more than internal louvers. Reflectors on louvers can be used to reflect light into 
the interior on dark days and bounce sunlight away on hot days.
Operating energy savings alone will often not justify retrofitting a building with a double skin.
However, it may be economical, where, for example, the building façade needs rehabilitation, 
or where noise from the exterior (eg the street) or interior (other rooms) is a problem. The 
type of double skin structure used will depend on particular user needs, building function, the 
existing building’s structural system, and/or priorities such as wind, noise, pollution or security.
There are several kinds of double skins, such as:
•
The ‘window box’ type where space is divided by rooms horizontally and vertically, like 
a bay window. This allows individual control of air intake and extraction as old air is 
expelled at the top of each window.
•
The ‘vertical shaft’ type, which uses a shaft configuration several storeys high. The used 
air can be vented into a garden storey for air cleansing. 
•
The ‘horizontal shaft’ type, which separates air circulation on each storey. It can be 
easily combined with balconies. In this case, vents are staggered to avoid bad air 
entering the next floor. 
Unfortunately, the vast majority of double skin buildings increase the heat island effect and 
create ‘dead’ spaces that do not have eco-productive or psychological benefits.