Glazing A Double-Pane Window With A Single Pane Of Glass

At the glass repair company where I work in Philadelphia, Pennsylvania, at least once a week we get a call from a business or homeowner with a broken double-pane window who asks us if we can replace it with just a single pane of glass.

Why in the world, you ask, would someone want to replace a double-pane window with a single pane? There are two reasons for this. One is the time factor. Double-pane windows (also referred to as a thermal or insulated windows) have to be custom-ordered and typically take between five and ten working days to be manufactured, whereas installing a single pane into the opening is something that can be done that very same day. The other reason is cost. As one would imagine, a double-pane window is more expensive After all, a single pane of glass is just that. Conversely, a thermal window, in addition to obviously having two panes of glass, also has quite a bit of technology built into it. And technology isn’t cheap. Replacing a large double-pane windows can be a significant expense.

As far as the actual job is concerned, converting a commercial double-pane window to a single pane is a relatively simple matter. For modern storefront glazing (known as “flush-glaze”) manufacturers sell a simple converter system that drops into the existing frame and re-configures it to a single-glazing width. Converting a residential window, however, is a different story. Residential frames and sashes are designed to hold a double-pane window (known as a “unit”) of a very specific thickness, and due to the proprietary nature of residential windows and no doubt a general lack of demand, there exists no converter system for this task. But that doesn’t mean it can’t be done. And done well, at that.

On a fairly regular basis I come across a homeowner or, more typically, an apartment dweller who, for one reason or another absolutely insists that they need to have their double-pane window repaired that very same day. It is for these customers I have developed the following method for doing such a repair, the result of which is semi-permanent (it can be easily reversed), and has an air-tight, water-tight seal.

After removing and disassembling the sash, then de-glazing the old thermal unit, a single piece of plate glass with a thickness of 3/16 or 1/4 inch (as opposed to the two pieces of 5/32 inch glass which is usually found in residential thermal windows) is cut to a size that fits snugly into the sash and is laid flat in a continuous bead of silicone on the inside of the exterior side of the frame. 1/16th inch thick neoprene setting blocks are then wedged along the edge of the glass, two per side. These act as a very effective shock absorber between the glass and the sash, and keep the pane from moving in any direction.

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