You should always replace broken glass as soon as possible, even if it is only cracked. Besides being dangerous, broken glass allows moisture to penetrate window parts which can create other more serious problems. In addition to this, broken glass panes are not only an eyesore but can greatly increase your heating and cooling cost.

To begin, the tools that you will need to complete this project correctly include a glass cutter, push points, putty knife, glazing putty, chisel, screwdrivers and a hammer. Also make certain to wear eye protection and gloves.

1. Remove all the broken glass. Use needle-nose pliers to remove small shards. Place all of the broken glass in newspapers and tape it shut before you throw it away.

2. Remove all of the glazing compound. There are a few different ways to remove glazing compound also known as putty from the rabbet. Try prying it off the sash with a scraper or a putty knife. If this method does not work, you also can try using an chisel to remove the compound from the window. Before doing so, be sure to score the compound by running a utility knife along a metal straightedge where the putty meets the wood. Be careful as you do this as you can easily damage the wood.

3. After removing all of the glazing putty, you will then need to remove the old glazing points. To do this, use some needle-nose pliers to remove all of the points. The points usually will come out easily once you have removed all of the glazing putty.

4. You will then need to measure for your replacement glass. Once you've removed all of the glazing compound and glazing points, measure the distances between the top and bottom rabbets and also the two side rabbets. Subtract 1/8 inch from both measurements to determine the height and width of the new glass pane. You can order your new piece of glass at most hardware stores.

5. Apply a exterior primer to the rabbet. Allow several hours for the primer to dry before going to the next step.

6. Install the new glass pane. Apply a 1/4-inch bead of glazing compound around the rabbet's perimeter, and press the glass pane into place to create a tight seal. Install glazing points at 8-inch intervals around the glass. Press the tip of the glazing point into the side of the rabbet, and use a stiff putty knife to wiggle the point into the wood.

7. Roll the compound between your palms to make it more pliable. Using your fingers, press the compound into the rabbet where the edge of the glass meets the window sash. Use a putty knife to smooth the glazing compound. Starting at one corner, drag the knife along the compound, molding it neatly against the glass as you go. Remove any putty that has been trimmed off.

This project is a simple fix for most homeowners. Just remember to take all of the safety precautions that I have already mentioned because broken glass can cause serious injuries. Take your time and be patient and take your time and you will be happy with the results. Good luck!