A building facade must consider a few functional and performance criteria:
The façade provides a barrier between the weather outside and the comfort expected by the building occupants inside. It protects the building from harsh weather, high winds as well as air and noise pollution.
A façade can aid the energy efficiency of the building by insulating walls and shading windows. This reduces the amount of energy required to heat or cool the building.
Façade materials must be durable and low maintenance. After all, they can be twenty floors up and hard to get to. They must withstand the most powerful storms and they must stay looking good without the need for regular cleaning and maintenance.
Façade safety is important too. The materials and designs should not contribute to the spread of fire. They should also help control condensation and moisture.