In this video, This Old House general contractor Tom Silva explains how to install a replacement window.
1 Pry the interior trim from around the old window.
2 Cut the sash cords, then lift the sash from the window frame.
3 Remove any storm sash or screens from the window.
4 Pull out old window frame from the opening.
5 Remove the sash weights from inside the wall on each side of the opening.
6 Fill any voids in the wall with fiberglass insulation.
7 Squeeze a bead of butyl caulk around window opening.
8 Apply expanding insulating foam along sill and to underside of expander flashing.
9 Place the expander on top of the new window.
10 Set the bottom of the window on sill, then press the top tight to the wall.
11 Secure window with four 2-inch stainless steel screws.
12 Apply butyl caulk along the jamb and new window frame.
13 Install PVC trim around the inside of window.
14 Caulk around the PVC trim, then nail on the window stops.