If you have a cracked or foggy double insulated glass window panes, you don't have to replace the whole window. Insulating glass is two glass panes that have an air pocket between them to serve as insulation for your home, so it is important that you replace the panes right away to keep energy costs low. Here are some tips to replace double insulated window panes.  

Prepare to Work

For this project, you need:

• work gloves
• an assistant
• pencil
• tape measure
• masking tape
• pry bar or chisel
• utility knife
• hammer
• single-edge razor blade,
• insulation
• glazing stops
• caulk and caulk gun,
• replacement double pane insulating glass

Before removing the glass, measure the height and width of the window opening at the broadest point. Make an "X" over it with the masking tape to help secure it while you remove it.

Order replacement insulating window glass within an eighth of an inch of these measurements. The extra measurements allow room for the window to expand or contract. Look for the wedge-shaped setting blocks on each side of the window, and mark their location with a pencil, because you will replace them later.

Remove the Broken Glass

Pull the glazing points that secure the glass with a pry bar or chisel on the inside and outside of the window; taking care not to break the trim. Get an assistant to hold the glass from the other side of the window, and slice through caulk with the utility knife.

Press the top of the glass in the direction of your assistant, then remove the pane and setting blocks. Use the utility knife to scrape extra caulk around the window sash.   

Install the New Glass

Apply a bead of caulk around the window frame, and add an extra bead of caulk where the setting blocks sit. Press the setting blocks firmly into the caulk. Center the bottom of the replacement glass on the lower part of the window frame, and press it against the caulk.

Caulk around the lower inside edge of the glass, and apply caulk six to eight inches up the sides of the glass. Reinstall the glazing points, and dab some caulk on them. Gently tap them with a hammer to push them in place.

Remove extra caulk on the glass with a single-edge razor blade. Let the caulk dry, then insulate any spaces around the window.

Replacing the double insulating glass window panes yourself saves money. If you don't feel comfortable working with glass, or the glass has shattered into many pieces, hire a glass repair service.