Most of the customers that I visit think that by having a broken or misted double glazed unit (glass) the whole frame needs to be replaced. Unless the frame itself has been damaged in a burglary or by accident the glass can be replaced without fitting a new frame.
Identifying the Glazing System:
The first thing to do is identify if the frame is externally or internally beaded. This is done by looking at the beads where they meet the inside edge of the window frame and identifying if there is a join there. Most new windows are internally glazed.
Removing the beads on internally beaded windows:
Insert a stiff putty knife into the join between the bead and the frame at the middle of the longest bead. You may need to push or tap the putty knife to separate the bead from the frame. Remove all of the beads one by one and the double glazed unit should be free to be removed and replaced.
Removing the Beads on Externally Beaded Windows:
There are a few different glazing systems on externally glazed windows. The most common one is the internal gasket or back wedge system. The rubber gasket on the inside of the window needs to be taken out to enable the external beads to be removed. To do this, take a stiff putty knife and press it into the rubber on the inside of the window and flick it out. Then follow the instructions for removing the beads above. Take note of which way the gasket comes out.
The next most common external glazing system is double sided security tape. The tape is put on to the window frame during manufacture and the double glazed unit is then pressed onto it, allowing the external beads to be clipped into place. Use a Stanley knife / Box cutter to cut the tape. Hold the knife flat to the glass to avoid slicing into the frame. Cut all round the taped area and you should be able to get the putty knife in and slowly lever the glass unit out. Once the glass has been taken out you can then get a scraper and remove all the old tape from the window frame, taking care not to damage the frame. Then follow the instructions for removing the beads above.
The third and least common type of glazing system is the sort that has no gasket or tape on the inside of the window. The beads on this type of frame can be removed from the outside with a putty knife. One word of caution With this type of frame, and some of the others. Some Externally glazed frames have Glass Locks fitted to them. Glass Locks are right angle pieces of metal that are inserted into special holder clips attached to the frame. If you remove the beads and see these metal clips, call a glazier as these clips can be very difficult to remove without the proper tools.
Measuring the Double Glazed Unit:
After removing the Double Glazed Unit it is advisable to take it to your local Glass Merchant for them measure it and check for any special coatings that the glass may have on it. If the Double Glazed Unit was sitting on plastic packers when you removed it, take them with you and ask the Glass Merchant if they are the correct packers for the job, if not, get the correct packers. This is very important as the cause of most Double Glazed Unit Breakdowns (misty / condensation between glass) is that they have not been fitted on the correct packers. If your window is glazed on security tape you will need to buy some new double sided security tape.
Re-Fitting an Internally Glazed Double Glazed Unit:
Make sure the unit is square in the frame and you have it sitting on your two packers. Fit the two shortest beads first by tapping the in with a nylon mallet. Then fit the two longest beads in the same way. You may need to push one end of the bead into position and bend the bead to get the other end in.
Re-Fitting an Externally Glazed Double Glazed Unit:
Back gasket system – Fit the glass and beads as described above and then push the rubber gasket back into the frame on the inside of the window. If the rubbers have shrunk you can gently stretch then out and re-fit them with a small blob of superglue in each corner to stop them from shrinking back again.
Security tape system – Fit the new tape to your window frame, taking care to keep it flush with the frame edge. Remove the covering and Spray the tape with window cleaner. This will allow you to move and align the Double Glazed Unit. The window cleaner will evaporate in a couple of hours leaving you with a Double Glazed Unit that can only be removed by cutting it out from the inside. Fit the glass and beads as described above.
One word of caution: Some Externally glazed frames have Glass Locks fitted to them. Glass Locks are right angle pieces of metal that are inserted into special holder clips attached to the frame. If you remove the beads and see these metal clips, call a glazier as these clips can be very difficult to remove without the proper tools.
If you are not sure which system you have or are not confident enough to proceed with the job, call a glazier. It will be cheaper in the long run to get someone who knows what they are doing than destroying your windows.