Double panes of glass lock in an air space between them to give an insulated window its energy efficiency. But care must be taken to remove all the moisture in the air space so the window won't fog up with moisture later.

To achieve that, the perimeter bars that will form the outer edges of the window are filled with a dessicant called sodium chloride. It's a base salt that will absorb any residual moisture that might remain after the window is put together. That moisture is absorbed through tiny holes on the inside edge of the perimeter bars. And the sodium chloride will never let go of that moisture once it's been absorbed.

The perimeter bars are then assembled, and crossbars are snapped into place. At this stage, every surface the glass will touch is cleaned, and the panes of glass are washed and thoroughly dried in a machine. The panes are placed on each side of the frame, and Lucite powder is sprinkled between the windows to keep them from sticking together.

A sealant is applied to the perimeter of each window. Then they're moved into an oven and heated to 100 degrees for several hours. It's here in the oven that the sodium chloride in the perimeter bars absorbs any humidity that may have been trapped between the panes of glass.

When they come out of the oven, the insulated windows are ready to be placed in whatever frames are desired, and they'll be 50% more energy efficient than a single, glazed window.