Passive cooling is a great way to avoid using air conditioning during the spring and fall in Phoenix. Some strategies for passive cooling include cross, stack, and night ventilation as well as solar shading and radiant barriers. Cross ventilation uses the wind to move cooler outside air through your house. You can optimize this by using large openings on one side of the room and smaller openings on the opposite side to create a Venturi Effect that speeds the air flow. Stack Ventilation takes advantage of temperature stratification and relies on two basic principles that as air warms, it becomes less dense and rises and that ambient air then replaces the air that has risen. Night ventilation is controlled by the homeowner and is very effective in the spring and fall months in the desert. When the sun sets and the temperature drops significantly, usually around 30 degrees, open the windows to allow the cool night air into the house. In the morning, close the windows to seal the house through the hot part of the day. With a well insulated house you can avoid using air conditioning until the night time low exceeds 70-75 degrees. Solar shading and radiant barriers help maintain a cool house by reflecting or shading the solar radiation from transmitting the heat into the house.