Replacement Window GuideAn awning window is hinged along its top edge and opens outward from the bottom. That geometry produces two practical effects that define the style: the open sash sheds rain like a small awning, and the sash seals by compression when closed, which is why awning windows rank among the most energy-efficient operating windows.
How an awning window operates
The defining feature is the top hinge. Andersen states that an awning window opens outward and is hinged at the top, so it creates a canopy over your window.
That canopy is what lets the window stay open during light weather. Andersen notes that the unobstructed opening it creates when fully extended allows in lots of fresh air and means you can even leave your window open in the rain.
Why awning windows seal so tightly
The awning's energy advantage comes from how the sash closes against the frame. Andersen states that with their single sash design that seals like a refrigerator door, awning windows are one of the most energy efficient types of windows.
Wind actually helps that seal rather than defeating it. Andersen notes that their seal tightens when the wind blows against them, because the pressure pushes the sash harder against the frame.
Reading the energy label
A tight seal shows up as low air leakage, but it is only one of the numbers on the label. ENERGY STAR explains that U-Factor measures the rate of heat transfer and tells you how well the window insulates, with lower being better, and that Solar Heat Gain Coefficient measures the fraction of solar energy transmitted.
Those figures are third-party results, not marketing. ENERGY STAR states that the energy performance of all certified windows must be independently tested, certified, and verified.