The glass skins may cover the entire structure or a portion of it, or they may span several structures. The purpose of dual glass layers is to create an air space that works as insulation against temperature extremes as well as noise, while allowing maximum daylight.
Undivided facades allow air to flow freely within the space between the inner and outer skins.
They are simple and inexpensive to build. This type presents several problems, but most importantly, noise, smoke, fire, and odors can move, unimpeded, from one space into another. Also, warm air accumulates at the top of the air space, while cool air pools at the bottom. Unless there are openings at the top of the facade to vent that hot air, the upper floors of the building will be hot on sunny days. Natural ventilation is best in shaft-type facades.