a double skin … rather than a thick skin



Wall systems with an inner and an outer face and a gap between the two is one type of facing or cladding system for more recent buildings that is not always obvious from the outside. In traditional systems, panels that form the outside wall - glass, metal, thin blocks of stone or whatever - usually have some form of insulation behind and sometimes integral systems for services such as wiring for power or even pipe work for fresh air or heating - although these services are more often set within a floor structure, hung from the ceilings or taken up through internal service ducts - and then there is an internal face of plaster or panels of wood or some form of composite but together these form a single integrated wall panel that is fitted between the floors or hung from the beams that form the roof. 

However, in some buildings, there is actually a substantial gap between the external face and an internal surface. Sometimes, this is because a façade was remodelled or upgraded and that space is necessary for a system that supports the outside wall and fixes it to the earlier building or the gap can be for an enhanced thermal barrier or a sound barrier or can be for an extensive system of beams or wires or ties whose structure allows thin internal and external walls, for instance in glass, but spanning a very wide opening or an opening rising up to a considerable height with little of what appears to be solid support.

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