Lockheed - Monarch™ Window System
You can choose to open double hung windows to capture ventilation as little or as much as you desire, from either the top or the bottom sash.
Picture windows are intended to provide an unimpeded view, as if framing a picture.
By adding special-shaped windows to a room, you are not only adding additional light but you are defining a room's shape and adding architectural interest.
Sliding windows are popular because they take up limited wall space and can be configured to suit virtually any size of wall.