Figure out which type of window replacement you’re doing: full frame replacement or a pocket replacement. A pocket replacement keeps the old frame and puts in a smaller window that fits within the frame. A full replacement is trickier and requires you to remove both the interior and exterior trims as well as the ext erior siding in many cases.

Measure for your replacement window. Measure the height on the right, left and middle of the window and the width and the top, middle and bottom. When ordering your windows, use the smallest height and width measurements. Double-check that the windows fit before you start installing.

Remove your old window. Please be aware that homes built before 1978 may have lead paint, and plan accordingly. First, remove your storm window or screen. It may lift out or need to be unscrewed. Next, score the window edge and then use a pry bar or putty knife to remove the frame. If your window is older, you may h ave sash weights or springs that will need to be removed. The last thing to be removed are the stops. If you are installing your window from the outside, remove only the exterior stops. If you’re installing from the inside, remove only the interior stops. Finally, fill any holes with wood filler to make sure you have solid places to screw in the new window frame.

The next step is to install the new window, which has several steps of its own. First, clean the window opening of all debris. Anything left can cause gaps and drafts. Apply flashing tape to the sill and up the bottom ledge of the interior side of the window. Check the sill for bowing and to make sure it’s level. Dr y fit your window. There should be a small gap around the frame. Apply caulk to the top of the frame, the stops, and sill. Place your window. Rest it firmly against the stops and into the caulk. From the opposite side of where you’re installing (inside if you're installing from the exterior and vice versa), drive the screws in. Make sure the sashes are laying evenly in the frame and ensure the rest of your window is even. Fill any exterior gaps with window spray foam insulation. Fill larger gaps with weatherstripping. Cut the sill adapter to the width of the sill. Drill two small holes, called weep holes, into the bottom of the adapter. This will help water drain. Lock it onto the window. Install your exterior trim. Seal the edges of the trim and the interior with caulk.