How to Weatherize Your Old Double Hung Windows

If you have leaky old double hung windows in your house like millions of people do and you want to do something about it. Please, do yourself a favor and weatherize them instead of replacing them. New windows are definitely more energy efficient than those in most houses, but replacement windows will take fifteen to twenty years to save enough energy to pay for themselves. However, for just a few dollars per window, you can install some weatherstripping and keep the cold air, dust and even some noise out of your house.

There are four locations where the air leaks in: between the sash and the jamb, between the bottom of the sash and the sill, between the top of the sash and the window head, and where the two sashes meet.

The best type of weatherstripping to seal the space between the sash and the jamb is a V-Shaped Polypropylene weatherstripping. It is sold under various names: Vflex, V-shaped Fin, V-Seal among others. This type of weatherstripping is secured to the jamb with a self adhesive strip and then the other half of the V presses against sash. The polypropylene is smooth, thin Sash Window Repairs Kent and durable enough for the sash to slide easily open and closed.

First measure the height of the sash and add 2″ to this when cutting the weatherstripping to length.

Tape the end of the “V” shut with a small roll of scotch tape, open the window all of the way and insert the tapes end up between the sash and the jamb with the closed end of the V facing toward the exterior.

Peel the paper off of the weatherstripping and secure it to the jamb.

Make sure that the paper is on the inside of the window so that you can close the window and pull the paper off the rest of the weatherstripping. Repeat this step on the opposite jamb.

If the upper sash isn’t painted shut or otherwise fixed in place, and you want it to continue to be operable, then you will want to install “V” weatherstripping along its jambs too.

The gap between the two sashes can be sealed in a similar manner. However, this time you should cut the weatherstripping a inch or two short so that it won’t get caught up at the jambs. Open the bottom sash a little and install the weatherstripping on the outside of the top of the lower sash with the closed end of the “V” pointing down. You may need to use a putty knife to push the weatherstripping down between the two sashes.

Sealing the space between the sash and the sill can be easily done with a strip of compressible foam tape. One thing to be sure of here is to clean the bottom of the sash before you apply the foam tape. Repeat this step for the space between the top of the top sash and the window head.