In a double hung window, both the upper and lower sash move. Look for the sashes that tilt in for easy cleaning. Ventilation is limited to half the area of the window. What to watch out for – The windows slide on metal or plastic tracks which make double hung windows only half as air-tight as casement windows. Look for quality materials and good weather stripping.
Single hung windows are like double hung but only the lower sash moves.
Awning & Hopper
Awning windows swing out from the top hinges and Hopper windows swing in from the bottom hinges. These windows are typically used for either attic spaces or clerestories (Awnings) or basements (Hoppers). They have compression seals which are very air tight. Either can be combined with a picture window to provide ventilation. These windows have some of the same hardware problems as casement windows, but since the windows hinge up and down you don’t have the same problems with warping.
Great for large unimpeded views and ventilation. When closed, compression seals make these windows very air tight. Make sure that the sash is fully clad or it will be vulnerable to water damage. Select windows with better hardware as casement windows can have problems with stripped crank handles and broken linkages with less durable hardware. Also, larger sashes can warp out of square over time making them harder to open and close. Occasionally lubricate the crank mechanism. Look for a well-built, sturdy sash with cladding on top, and stronger, durable hardware.