When selecting windows for a project, it’s also important to consider how they’re operated. Some operating types have lower air leakage rates than others, which will improve your home’s energy efficiency. 

There are numerous window operating types to consider. Traditional types include the following:

• Awning
  Hinged at the top and open outward. Because the sash closes by pressing against the frame with mechanical closing devises, they generally have lower air leakage rates than sliding windows.
• Casement
  Hinged at the sides. Like awning windows, they generally have lower air leakage rates than sliding windows because the sash closes by pressing against the frame.
• Fixed
  Fixed panes that don’t open. They are the most airtight but not suitable in places where window ventilation is desired. In rooms with many windows, consider using some fixed ones to reduce cost and air leakage.
• Hopper
  Hinged at the bottom and open inward. Like both awning and casement, they generally have lower air leakage rates because the sash closes by pressing against the frame. This type will allow rain in more easily if left open.
• Single- and double-hung
  Both sashes slide vertically in a double-hung window. Only the bottom sash slides upward in a single-hung window. These sliding windows generally have higher air leakage rates than projecting or hinged windows.
• Single- and double-sliding
  Both sashes slide horizontally in a double-sliding window. Only one sash slides in a single-sliding window. Like single- and double-hung windows, they generally have higher air leakage rates than projecting or hinged windows. 

Click here to read more about Operating types from the Efficient Windows collaborative.

* US Department of Energy. ONLINE. 2006. Available: http://www.eere.energy.gov/consumer/your_home/windows_doors_skylights/index.cfm/mytopic=13370

 [24Mar2006]