|Emissions Reduction Toolkit||Climate Resilience Toolkit||Climate Resilience Guidelines|
Benjamin Benschneider and Olson Kundig Architects
Cross ventilation relies on wind for cooling. When wind blows on a building, a pressure difference is created between the windward (wind-facing) and leeward walls. Openings (i.e. windows) placed on opposite sides of a building will allow the cooler external air to enter the building while warmer internal air is sucked out from the leeward side openings. The degree of passive cooling is determined by the size and placement of the building and ventilation openings, as well as the regularity of wind. As a result, while cross ventilation can provide effective cooling, it can also be unreliable when naturally occurring wind is not available. As a result, larger buildings will typically require mechanical ventilation systems or passive stack ventilation in order to ensure ventilation continues in the winter and when wind is unavailable.
For cross ventilation to be effective, the building must be in a location with regular summer winds. The windward wall should ideally be oriented to be perpendicular to typical summer wind; perpendicular orientation may not always be possible in existing buildings. The building itself should ideally be relatively narrow to ensure fresh air is distributed throughout the building. Extensive internal partitions will inhibit air flow and render cross ventilation impractical. Assuming a building’s location and orientation allow for cross ventilation, operable windows/openings are required to ensure effective ventilation. Given the extensive building conditions required, it is typically more practical to design a new building for cross ventilation rather than retrofit an existing building. However, if the building conditions are met, retrofitting for cross ventilation can be a cost-effective, energy efficient passive cooling strategy.