Thermal insulating glass units are distinguished by the incorporation of at least one sheet of selective glass. Such glass units are an excellent choice for residential or other buildings in harsher climates.

Replacing one pane of glass with a selective pane in a standard single-chamber glass unit almost halves the thermal conductivity of the glass unit. Thermal conductivity can be further reduced by replacing the air in the glass envelope with an inert gas, by replacing argon with krypton, or by increasing the gap between the glass sheets up to 20 mm. In this case, the thermal conductivity of a single chamber glass unit will be Uf≥1.0 W/m²K. 

The best results in heat retention can be achieved with double chamber glass units. By replacing the air with inert gas and installing selective glass in place of both outer panes, a thermal conductivity of Uf=0.6 W/m²K can be achieved. 

Double chamber thermal insulating units weigh more, but are suitable for both plastic and wooden window profiles. The opening mechanisms are also perfectly capable of supporting this weight, but care should be taken when adjusting them.