Double glazing units are consisted of two (or three) panes of glass separated by a spacer bar – the spacer bar being filled with an insulating desiccant in order to absorb moisture – and sealed together at the edges with an inner primary seal (butyl) plus a secondary seal (polyisobutylene). Between the two panes, air cavity can be filled with gas, i.e. argon for an enhanced insulation.

External facades are mainly responsible for the energy balance inside buildings and as such with the installment of double and triple glazing and choosing between combinations; an excellent thermal insulation performance can be realized. During winter the cold is restricted from penetrating indoors, while on summer solar radiation is reflected away and heat inside the buildings is significantly eliminated.