Panes

• Double-hung windows get their name from the fact they they have two individual panes of glass that can be operated. These two windows are called sashes, and they are set up one in front of the other in a frame. The sashes slide up and down vertically and are separated by a piece of wood called a parting strip. In the old days, there were pulleys and weights on the inside of the window frames that would slide up and down when the window was being operated. These days, they are built with tension-loaded springs inside the frames instead. When they are both closed, there is a turning lock in the middle that keeps them tightly together and forms a good seal so there is no air being lost.
  
  

Cleaning

• The outside of windows are always getting dirty and they are always in need of cleaning. Double-hung windows are no different. They can actually be cleaned from the comfort of the inside of your house. This is especially beneficial when they are two or more stories high. They come equipped with release mechanisms that allow you to tilt the window inside a room where you can easily clean it. They can actually even be removed altogether (See resources link for cleaning).
  
  

Replacement

• Double-hung windows are used in new construction, but they are also very popular in remodeling as well. When this is the case, a measurement is taken in the existing window that takes into account the width and height in that order. The width measurement is taken from the area that the existing window slides up and down in. You measure this distance from the right to the left at the top, the middle and the bottom. You then take the smallest of these measurements and subtract by 1/4 inch. To get the height, you measure from the top to the bottom at the right, the middle and the left. You then take the smallest measurement and deduct 3/16 of an inch. Then you write down the measurements and your windows are custom made at those dimensions.