Check the Fit

• Most storm windows, both double and triple track, are hung outside of the house. This is convenient because you can continue to open and close your inside windows and do not have to take the storm windows down every year. These combination storm windows will attach directly onto the window frame on the outside window. Before you actually install the window, place it in the frame to make sure it fits properly. If there are already screw holes drilled in the flanges (the holes drilled through the storm window to attach it to the window), be sure they are all centered over the window frame.
  
  

Drill Holes and Caulk the Window

• If there are not pre-drilled screw holes in the storm window, you will have to drill them. Drill the holes in the storm window flanges about 12 inches apart. Then apply caulk to the outside edges of the top and sides of the window frame. Make sure the caulk is not in lumps or the window will not sit level. Do not caulk the bottom edge of the storm window until you have the storm window in and securely fastened.
  
  

Install the Window

• Place the storm window into the frame and center it in the main window. Check that the bottom of the storm window touches the window sill. Leave a little space at the top so the storm window casing has the room to expand when the temperatures change. Check that the window is straight. The seal will not be secure and air will seep in if the window is crooked. Once the storm window is placed, make sure the screen sash and window sash are able to move smoothly. If not, the frame is probably not straight and will have to be adjusted. Secure the window by installing sheet metal screws with a drill in the pre-drilled holes. Begin with the top and continue with the other sides. Do not tighten the screws too tight or you will warp the frame. Once the storm window is fastened, caulk the bottom edge.
  
  

Examine Your Work

• After the storm window has been installed, examine the caulk seal to make sure it is tight. Check that the frame is straight and that it is not warped around the screw holes. Make sure the sashes move smoothly, and you are finished.