Insulated Glass, often called double glazing, is a combination of two or more panes of glass spaced apart with a spacer bar and hermetically sealed with a primary and secondary sealant to form a single unit with one or more air spaces in between. IG units improve the thermal performance, thus significantly reducing heating and air-conditioning costs. IG units also reduce interior condensation in cold climates, and increase comfort near windows, thus maximizing the usable interior space. IGU Surfaces: The IG unit consists of four surfaces. Surface 1 is that side of the glass lite that faces the exterior of the building. Surface 2 is other side of the Surface 1. Surface 4 is the side of the glass lite that faces the interior of the building. And the Surface 3 is the other side of surface 4.
The formula used to calculate the amount of gas to be filled into the IGU is given here.
Height (cm) x Length (cm) x ID (mm) x 0.001 = Number of Litres (x)
Number of Litres (X) x 1.5 = Number of litres of gas required per window