In this video, This Old House general contractor Tom Silva explains how to install a storm window.
Steps:
1. Measure window width in three places at bottom, top and middle of window.
2. Use smallest dimension to order new storm window.
3. Measure window height from outside.
4. Unscrew and remove the old storm window from house using a drill/driver.
5. Scrape loose paint from window frame and window trim.
6. Drill small weep holes in exterior of windowsill.
7. Prime and paint the exterior window frame and trim.
8. Apply a bead of butyl caulk to the rear of new storm window, but only along top and sides.
9. Screw top of storm window to the window frame.
10. Close bottom sash, then screw sides of the storm window to window frame.
11. Use hammer and putty knife to tap down the adjustable expander tight against the windowsill.