Window Repair

• If you want to keep the look of your existing windows while increasing the energy efficiency of your home, repair your window sash. The window sash includes the pane of glass, along with the frame surrounding it. Most windows come with two sashes: a lower, movable one for opening and closing and an upper one.
  
  To repair the sash, begin by removing it from the window fittings. Take care when removing the sash to keep the cords or chains that operate the window from being drawn into the weight pockets holding the counterbalances. You can do this by tying a knot in the cord or chain ends after removing them from the lower sash.
  
  Once you've removed the sash, remove the glass from the frame. Soften the old putty holding the glass with a heat gun set to medium, using a nozzle shield. Scrape away the softened putty using a putty knife and pry the glass from the wood.
  
  Clean any loose or open joints, removing damaged or softened wood, and then rebuild the joints using epoxy filler. When the epoxy has cured, sand it smooth with 100-grit sandpaper, and seal the wood with oil-based primer to keep the wood from drying out the epoxy. Replace the glass in the frame, bedding the glass in glazing compound. Once bedded, give the glazing compound a week to dry. Paint the sash and glazing, including an oil-based primer beneath the final coat of paint. When the paint has dried, return the sash to the window frame, installing the cords and weights where necessary. For additional energy efficiency, install new weather-stripping when you're reinstalling the sash.
  
  

Replacing a Sash

• At times, repairing the sash isn't an option, and the entire sash must be replaced. For complete replacements, buy a sash kit, which includes everything you'll need to do the job. Kits are available from many of the largest window makers, such as Pella, Marvin and Anderson. Replacing a sash lets you get the full effect of energy-efficient design while retaining the existing window frame.
  
  You can find a kit to fit most common window sizes, and sash kits can be made to measure for irregular windows. Sash replacement using a kit is a simple process. You remove the old window sash and the accompanying hardware for controlling the window, including any counterweights, cords and chains. You then attach the new supporting system and slide in the new sash.
  
  You can replace a sash quicker than repairing one and with a savings in cost over hiring a carpenter to do the job for you. In 2009, a carpenter charges on average $415 for a 30-inch-by-54-inch window, whereas the average kit of the same size costs $325.