Window awnings improve comfort by stopping the sun's heat before it reaches the glass. This simple principle has been used for centuries and remains one of the most effective passive cooling strategies available today.
Why Awnings Work
Two Foundational Principles
01/ Windows Are the Primary Pathway for Solar Heat Gain Inside
Research has consistently shown solar radiation through windows is the largest contributor to heat gain in buildings. Heat from the sun entering through roofs, walls, doors, and air infiltration is significantly smaller. Blocking heat gain largely happens at the window.
When sunlight passes through window glass the solar radiation enters as short-wave radiation, it is absorbed by interior surfaces, and emits heat back as long-wave radiation, which cannot escape back out through the glass, trapping the warmth inside.
02/ The Greenhouse Effect is Real
Stop the heat before it enters to avoid the greenhouse effect!
Photo: Morningside Avenue, Harlem / Courtesy Greater Astoria Historic Society
It is not surprising that before we had air conditioning, awnings were widely adopted throughout New York City and well beyond to dramatically improve thermal comfort.