Insulated Glazing - Construction

Construction

IGUs are manufactured on a made to order basis on factory production lines. The width and height dimensions, the thickness of the glass panes and the type of glass for each pane as well as the overall thickness of the unit must be supplied to the manufacturer. On the assembly line, spacers of specific thicknesses are cut and assembled into the required overall width and height dimensions and filled with desiccant. On a parallel line, glass panes are cut to size and washed to be optically clear.

An adhesive sealant (polyisobutylene - PIB) is applied to the face of the spacer on each side and the panes pressed against the spacer. If the unit is gas filled, two holes are drilled into the spacer of the assembled unit, lines are attached to draw out the air out of the space and replacing it with the desired gas. The lines are then removed and holes sealed to contain the gas. The more modern technique is to use an online gas filler, which eliminates the need to drill holes in the spacer. The units are then sealed on the edge side using either polysulphide or silicone sealant or similar material to prevent humid outside air from entering the unit. The desiccant will remove traces of humidity from the air space so that no water appears on the inside faces (no condensation) of the glass panes facing the air space during cold weather. Some manufacturers have developed specific processes that combine the spacer and desiccant into a single step application system.

The double glazed window was invented in 1930s, and was commonly available in USA in the 1950s under the ThermopaneTM brand name, registered in 1941 by Libbey-Owens-Ford Glass Company. After so many decades, the manufacturing process is well established. The brand name Thermopane has entered the vocabulary of the glazing industry as the genericized trademark for any IGU.

Materials which can be used for double glazing are versatile and include aluminum, PVC, and wood (timber).