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How to Replace Insulating Glass

Don’t put up with foggy or cracked double pane windows. You can replace them yourself and save the major cost of professional repair. We show you three ways to take the sash apart so you can install the replacement glass.

By the DIY experts of The Family Handyman Magazine

  • ComplexityComplexityComplexity Moderate
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    Complexity depends upon the window assembly method. Two of the three replacement techniques are simple. One is more difficult.

Repair strategy and buying materials

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

But it’s not always that easy these days. There’s 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 you’re better off turning them over to a pro. We’ll 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 you’ll need from the repair specialist. Ask for advice so you’ll know whether the job’s just too big for you to get into, or not worth the money you’ll 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. We’ll show each method, starting with the easiest.

Removing window sashes

Most insulating glass sashes are easy to remove if they’re the type that you can open. But you can’t 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.

  • DOUBLE-HUNG windows slide up and down. Those with insulated glass almost always slide against vinyl jamb liners on the sides. To remove the sash, depress the liners slightly, then pull out the top part of the sash. Twist the sash to release one side from the counterweighted springs that connect to the sash bottom. To reinstall it, put the bottom in first and reverse the procedure.
  • CASEMENT windows are hinged on one side and swing outward when you turn a crank. The swing arms that hold them usually have release catches. But if you can’t figure out the release mechanisms, simply unscrew the arms at the top and bottom to release the sash. Have a helper support the window while you unscrew it.
  • SLIDER windows move horizontally. You can usually remove them just by lifting the sash and swinging out the bottom. If nails holding the trim in place prevent you from lifting the sash, cut the nails with a side-cutting pliers or a hacksaw blade, or pull them out.

Method 1: Gasket seal

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:

  • Our photos show dismantling a wood sash, but sashes may also be vinyl or aluminum, and they usually come apart the same way.
  • Be careful not to damage the old gasket, so you can reuse it. Replacement gaskets can be hard to find.
  • Always use “neutral cure” silicone for caulking (Photo 4).
Gasket seal on window

Gasket seal on window

Figure A: Window with gasket seal

Method 2: Adhesive tape seal

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 you’ll 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:

  • Pry out the stops, being careful not to bend or break one. Replacements can be hard to find.
  • Some stops can’t be removed without ruining them. Ask the repair specialist if your windows are this type, and buy new stops.
  • Buy double-face glass sealing tape of the correct thickness and width from the repair specialist.
  • If the stops are caulked in place, slice through the caulk with a utility knife.
  • If the window has “setting blocks” (to keep the glass centered in the frame, as in Photo 4), reposition them exactly as you found them around the old glass. But check the fit of the glass first. You may have to alter the thickness of the blocks.
Setting tape seal

Setting tape seal

Figure B: Window with a setting tape seal

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

Method 3: Caulk seal

Insulating glass that’s caulked in place is virtually glued to the frame. In addition, it’s 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 it’s 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:

  • Wood stops are usually stapled and painted in place. There’s a pretty good chance you’ll crack them when prying them off (Photo 1). Pros break them too. Work carefully, save the pieces and glue them together later. Finding matching replacement stops can be tough.
  • The wood frames themselves sometimes crack when you pry out the glass. A heat gun, set on low, will soften the adhesive to get the glass out easier, and you’re less likely to damage the wood.
  • Careful; don’t nick the glass when you nail the stops back in.
Caulk seal

Caulk seal

Figure C: Window with caulk seal

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

Glass warranties

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 don’t 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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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

    • Hammer
    • Caulk gun
    • 4-in-1 screwdriver
    • Drill/driver, cordless
    • Dust mask
    • Pry bar
    • Putty knife
    • Utility knife

Gloves, Goggles, Heat gun

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

    • New insulating glass unit
    • Silicone, neutral cure
    • Glass setting tape

Comments from DIY Community Members

Share what's on your mind and see what other DIYers are thinking about.

1 - 8 of 8 comments
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June 05, 1:47 PM [GMT -5]

I have tried to find a supplier of dual pane glass - it is near impossible. They all want to install for a fortune and give the glass for a fair price - where do they get the glass from?

PS the guy that responded is fake - the website is for sale - 280.- !!

December 17, 1:48 PM [GMT -5]

More times than not, you have to be a glass company (glazier) to purchase insulated glass. You may be able to find a local vinyl window manufacturer to make you a glass unit byt the odds are slim. windowRepairGuy .com is a good start to find a local glazier in your area.

December 17, 1:44 PM [GMT -5]

Let's face it. By the time you remove the sash from the frame, find a place to buy the insulated glass, purchase all the proper adhesives to glaze the glass back into the sash, purchase safety glass and cut proof gloves, etc. etc. This job may be better suited for a pro not to mention it will probably cost less in the long run.

December 08, 12:14 PM [GMT -5]

I cannot find anyone that will provide just the double pane glass. Adding a list of companies who will do this would be helpful.

November 27, 11:17 PM [GMT -5]

E Glass Company is a full service manufacturer providing Low Profile Insulated Glass units. We offer a full line of Low E glass, Grid options as well as Argon and Krypton gas. We offer many more products as well such as mirrors, tempered glass, laminated glass, restorations glass and much more. If you are looking for a competitive glass manufacturer look no further give us a call today. We ship to anywhere within the United States.

We look forward to hearing from you!

Erik Slapp
E Glass Company
Tel (717) 479-6745
Fax (717) 441-3821

October 27, 6:51 PM [GMT -5]

Neither of these 2 scenarios match my situation. I have a single hung, aluminum window. The upper, fixed sash is compromised. I have a replacement sash, have successfully removed the old sash which is held in place by 2 vinyl retention strips, one on each side. When installing the new, replacing the vinyl stop strips was a problem that I did not resolve for fear of breaking the new sash. I ended up reinstalling the old sash with little difficulty and that's where it stands.

The new sash is identical to the old BUT, these windows have a felt, weather strip seal on the outside panel that is a little thicker on the new panel. I suspect this is normal in that the old is compressed but the slight increase in thickness makes installation of the vinyl retention strips require more than just firm pressure.

I would contact the manufacturer of the window but have no idea who that is. Not having any prior experience with this I'd like some insight from one who does.

I'm thinking a little WD-40, a wooden block, a corrugated cardboard sheet to protect the glass and some gentle taps with a hammer..........maybe. Any advice would be appreciated.

July 26, 12:51 PM [GMT -5]

By following the directions given on your site, I was able to replace the glass on the fixed portion of my vinyl slider window. I used a 3" putty knife, tapping it in between the glass and the frame with a rubber mallet, to break the seal of the glazing tape on the frame. Very easy. Then while my wife gently pushed the panel from the inside, I removed the panel (from the outside). Tedious was the removal of the residue left over from the glazing tape UNTIL I got out the Goof-Off. Cleaned up quickly. Advise caution when handling the replacement glass: take great care not to subject the edges, especially the corners, to any stress---the glass will chip. Special handling needed when you actually insert the replacement glass: don't force the replacement panel. Further, with glazing tape, you only get ONE chance to seat the glass in position--if it is misaligned after it has contacted the tape, it cannot be adjusted. My guess is that caulk is more forgiving. If you are having problems figuring out how to measure the glass so that you can order the correct size, if you take off the plastic trim pieces on the outside of the window, you can measure the exact size of the old glass (still in place). This includes, length, width and thickness. The place I ordered the glass from merely wanted the "daylight only" size, meaning, when you look out your window from the inside, what is the actual glass opening. Then they added the appropriate length/width to accomodate the actual frame size. I did have to eyeball/measure the thickness. I think the choice given me by the glass company was "5/8 or 1 inch" and it was clearly more like 1 inch. The panel they delivered was the exact same size as the old one so the "daylight only" method worked quite well. The window I replaced was a small unit. For my first attempt, I'm glad it was small. Took a lot of stress out of the project because the unit was easy to handle. If one is contemplating replacing a large unit, I strongly suggest they have a helper, especially when it comes time to actually seat the new unit.

June 19, 12:11 AM [GMT -5]

Hardest part of this project is finding someone to custom make your replacement window panes. Measure for the replacement glass pane very carefully. If the replacement glass pane is too tight a fit to the frame, beat on the frame with a rubber mallet until the glass fits. I have successfully used butyl caulk to seal the glass to my frames rather than the sealing tape. The butyl caulk does not harden like regular caulk. I also bought a set of suction cups to pull the glass from the frame. Breaking out the glass seems so crass. Many outlets sell the suction cups including Harbor Freight. I bought two sets, one for me and one for my helper. If you have to leave the frame in place, you will need the suction cups to lift the new glass pane into place anyway.

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