If your house has drafty single-pane window sash inserts, you are losing costly energy every day. Instead of a complete replacement of your old single-pane double-hung windows, you can buy new window sash insert kits with dual-pane glass that you can install yourself in existing double-hung window frames. Sash replacement allows you to reduce window heat loss, while keeping your existing indoor and outdoor window trim.
Measure the jamb-to-jamb width of your existing window. Record the measurement. Measure the sash opening height. To measure, open the lower sash. Place the base of your tape measure at the point where the exterior side of the lower sash meets the window sill. Extend your tape measure up through the lower sash to the jamb at the top of the window. Record the measurement.