• A bay window expands your view.view through the window image by Ni Chun from Fotolia.com
  
  A bay window is not one window; instead, it is three windows that function as one unit. A bay window configuration projects from an outer wall and forms a recess, or bay, on the corresponding interior wall. The design is especially useful for its ability to gather light and provide an expansive view. Window manufacturers sell bay window packages that are already assembled and ready for installation. Their frames are made from aluminum, vinyl and wood.
  
  

Three Window Frames

• In a bay window design, a center window projects out from the house wall. Two side windows meet the house wall at an angle of about 30 to 45 degrees. The center panel sash---also known as a frame---is customarily larger than the windows on either side. Often, the center window is fixed and does not open. The two windows on the sides of the center window are usually operable windows, meaning they permit ventilation. They are commonly either casement windows, meaning they are hinged, or they are double-hung sashes that open via a sliding mechanism.
  
  

Three Window Panes

• For energy efficiency, new high-performing bay windows often use two layers of glass with argon gas between, and the glass is coated with a microscopic film called a Low-E coating. This window technology maximizes the window's ability to halt damaging ultraviolet rays of the sun without obscuring the view through the window. At the same time, it insulates to keep the interior cool in hot weather and keep the heated air in during the cold season.
  
  

Window Roof

• Because a bay window juts out from the house exterior, it must be roofed to seal out weather. In some bay window designs, the three-panel window has a roof made of materials that match the house roof. In other designs, the window covering is made of a contrasting material.
  
  

Window Seat

• Large bay windows often include shelves or window seats in the interior space they create. A shelf that aligns with the interior house wall and extends to the base of each window can be a place to set potted plants, books or curios. A window seat that extends across all three windows provides a decorator touch and allows for seating with storage space under it.