How to Replace Insulating Glass | The Family Handyman

Repair strategy and buying materials

It used to be that a broken window was a cheap fixa piece of glass, some glazing compound and a few minutes workand then tell the kids to play ball somewhere else next time.

But its not always that easy these days. Theres a lot of high-tech, double-pane insulating glass around that not only gets broken but also can lose the seal between the panes and permanently fog up. Replacing a piece of insulating window glass gets expensive. And often you have to hire a pro to do the job, which can get very expensive.

This article shows how you can cut this cost by replacing insulating glass yourself. Sometimes the job is so easy that almost any novice can do it. But other windows can be so difficult that youre better off turning them over to a pro. Well tell you how to figure out whether you can do it yourself.

Repair strategy Start by removing, if possible, the entire sash containing the broken or fogged-up insulating glass (see Removing Window Sashes). Take it to a window repair specialist at a glass shop. Look under Windows or Windows, Repair in the Yellow Pages, and call first.

The specialist will measure the size and thickness of the glass panel, help you identify the manufacturer and determine if a fogged-up window is still under warranty (see Window warranties). Some special kinds of glass like low-E and gas-filled units must be special-ordered.

The window specialist will estimate the price of new glass and also tell you the cost to install it in the old frame. Installation costs will double or triple if the specialist has to come to your home. Prices can vary quite a bit, so call around to compare prices of both the glass and the installation.

If you buy the glass and install it yourself following our step-by-step photos, also buy any of the supplies youll need from the repair specialist. Ask for advice so youll know whether the jobs just too big for you to get into, or not worth the money youll save. Keep in mind that glass dealers may not warranty the glass if you install it yourself. Be sure to ask. You should expect a 10- to 20-year warranty against seal failure.

Manufacturers install glass in window frames in three different ways: with gaskets, adhesive tape or caulk. Well show each method, starting with the easiest.

Most insulating glass sashes are easy to remove if theyre the type that you can open. But you cant always remove stationary sashes. These have to be repaired in place. Here are the most common types of openable sashes and how to remove them.

Take out the screws that secure two diagonally opposite corners. Leave the other two corners fastened to help you reassemble the frame squarely.

Tap the frame loose from the gasket and glass with a wooden block and hammer. Be careful not to mar or damage the frame. Use a piece of old carpeting if necessary

Remove the old gasket and wrap it around the edges of the new insulating glass unit. Then push the frame pieces back together around the gasket, tapping it tight with a hammer if necessary.

Seal the gaps in the corners with a small bead of clear neutral-cure silicone to keep out water.

In this installation method, the edges of the insulating glass are wrapped in a one-piece molded gasket of vinyl or neoprene. The frame is held together by four screws, one at each corner. The grooves in the frame hold the window in place. Sashes assembled by this method usually come apart easily, and they are just as easy to reassemble.

Some additional tips:

Pry out the stops with a thin pry bar or thin-blade putty knife. Usually you'll need to begin at the top, then do the sides and finally the bottom.

Flip the window over. and slice through the tape bond with a thin, flexible putty knife or a utility knife. If you can't slide the knife in, you'll probably have to break out the glass, as shown in Method 3, Photo 3 below .

Lay the new tape in place after you scrape the old tape and adhesive from the frame and clean off any remaining adhesive with paint thinner or solvent.

Position the glass against the setting blocks and drop it in place. Take care: Once the glass touches the tape, it adheres and can't be adjusted. For accurate placement of a glass panel larger than the one shown, lean the frame against a wall and have a helper steady the frame while you set the bottom edge in place, then tip the panel into the frame. After the glass is in place, replace the stops and caulk any gaps at the corners with clear silicone.

Some windows are sealed with double-face adhesive setting tape. Usually these windows have removable vinyl, aluminum or wood stops on one side, with the adhesive tape placed between the glass and the frame on the other. The tape is usually 1/16 in. or 1/8 in. thick, so youll have enough room to slip a thin-blade putty knife or utility knife between the glass and frame to slice through the tape.

Some additional tips:

This is a cross-section of an insulated-glass window.

Pry off the stops with a thin pry bar and/or stiff putty knives. Work them off gradually to avoid breaking them and damaging the frame

Flip the window over and try to cut the caulk with a utility knife. Sometimes the caulk is weak, and the glass comes free. But usually it won't, and you'll have to break the glass, as in Photos 3 and 4.

Turn the window over again, cover the glass with cardboard and smash it as close to the frame as possible with a hammer. Wear goggles, a dust mask and leather gloves for safety.

Pry the glass out piece by piece. If the frame shows signs of cracking or chipping, use a heat gun to soften the adhesive. Then scrape and clean the edges. Keep the work surface clean or padded so you don't damage the frame surfaces.

Apply a bead of clear neutral-cure silicone to the frame and drop in the new insulated glass. Make sure any setting blocks are properly positioned. Then run a thin bead of caulk along the backside of the stops and tack them in place with 3/4-in. brads spaced every 6 in. Let excess caulk dry, then scrape it off with a razor scraper.

Insulating glass thats caulked in place is virtually glued to the frame. In addition, its held by a stop, which might also be caulked and very difficult to cut through with a knife. You might have to smash out the window, then pry out the glass piece by piece (Photos 3 and 4).

Tip: For easy cleanup, place glass on top of a sturdy tarp to catch all the shards. Many wood frames have the glass caulked in place, and its difficult to replace the glass without damaging the frame. So you might want to consider having a window repair specialist handle this glazing method. If you do it yourself, allow at least a couple of hours to remove the old glass and clean the frame. Some additional tips:

This shows the anatomy of an insulated-glass window with caulk.

Most insulating glass now carries a 20-year warranty against defects and seal failure. Older windows may carry a 5- or 10-year warranty. Seal failure is the most common problem. You know the seal has failed when moisture begins to appear between the two panels of glass.

Tip:: Check your warranty at the first sign of fogging.

The fogging might not be all that irritating at first, but in a few years it will be, and by then your warranty may have expired. If you dont know the window manufacturer, a repair specialist can help you identify the unit.

Major manufacturers usually put tiny identifying marks on the window hardware, the glass spacer or the glass itself. Sometimes these marks include the date the unit was made.

KEEP IN MIND: Warranties cover the new insulating glass unit but not the cost of installation.

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How to Replace Insulating Glass | The Family Handyman