Things You'll Need
Backer rod sealant
Pella is one of the leading manufacturers of windows. The company offers a variety of windows with different styles and features, including double-hung and casement windows in vinyl, wood or a fiberglass composite. Pella also offers replacement sashes so the entire frame of the window does not have to be replaced. Replacing only the sash requires less manual labor and much less time than replacing a whole window.
Remove the interior stops running along the sides of the window with a pry bar. Slide the pry bar under the trim and pull up to begin moving the trim. Take off the stop trim on both the sides and along the top of the window.
Cut the balance cords on the lower sash with scissors and tilt the lower sash back down toward the inside of the house. Remove the bottom sash and set it aside. Remove the wedge on the bottom of the upper sash in the window with a chisel.
Slide the upper sash down the window and cut the balance cords with scissors. Tilt the upper sash toward the interior of the house and remove it from the window. Unscrew and remove the pulleys for the balance cords located along the jamb of the window frame.
Tilt the complete replacement sash into the opening and lay a level across to make sure it is plumb and square. Remove the window and run a bead of caulk along the inside jamb of the window and across the bottom sill.
Set the window back into the opening and raise the bottom sash to install two screws into the bottom of each side of the window and into the jamb. Repeat the process for the top sash and continue around the entire window. Install plastic plugs in the screw holes along the jamb liner.
Seal the space between the new window frame and the existing window frame with backer rod sealant. Reinstall the old sash stops and new trim around the window.
Apply a bead of caulk along the exterior of the window at the sill to seal it properly. For extra insulation, go around the entire perimeter of the window.