Expert Series Part 1: What is an Insulating Glass Unit?

Source: Guardian Glass Expert Series

An insulating glass unit (IGU) is a glazing assembly comprised of two or more lites of glass separated by one or more hermetically sealed cavities, filled with either air or inert gas. The configuration delivers superior insulating performance compared to monolithic (single pane) glazing, by reducing air-to-air heat transfer in the building envelope. When used in conjunction with low-emissivity (low-E) glass coatings, IGUs become an efficient mechanism in reducing heat-transfer, conserving energy and enhancing occupant comfort while also providing the benefits of natural light.

Measuring Performance, read more...

The unit of measure for how well an IGU insulates is U-value. U-value measures how much heat will transfer through an IGU. The lower the U-value, the better the IGU insulates by reducing heat flow. The U-value of a 1” overall width IGU with argon fill and a low-E coating is 0.25 (Btu/h-ft2-F) which can be compared to the U-value of monolithic 6mm glass which is 1.0 (Btu/h-ft2-F).