Natural ventilation is the removal of vehicle exhaust and heat from a parking structure through openings in its exterior walls, using wind and air movement rather than fans. A garage that qualifies is classified as an open parking garage and avoids the cost and energy of mechanical ventilation.
Under the International Building Code, an open parking garage must have uniformly distributed openings on two or more sides. The area of the openings in each tier must be at least 20% of the total perimeter wall area of that tier, and the aggregate length of the openings must be at least 40% of the perimeter of the tier. Interior wall lines and columns must also be at least 20% open. Local amendments can differ.
Why it matters
- Cost. No exhaust fans, ductwork or carbon monoxide controls, and lower operating energy.
- Code path. Open garages are treated more favorably for fire protection, construction type and allowable size than enclosed garages. See open-air facility and enclosed parking garage.
- Design. The openness rules shape facades, screening and how much of the structure can be buried or wrapped. See openness calculation.
Design cautions
- Decorative screens and mesh count against openness unless their free area is credited.
- Below-grade levels and wrapped garages usually cannot qualify and need mechanical ventilation.
- Openings bring rain, snow and noise into the structure, which affects drainage and durability.
The Parkonomics view
Natural ventilation is free air that pays for itself every year. Protect it early in design, because a facade decision made late can quietly turn an open garage into an enclosed one.
Related terms: Openness Calculation, Open-Air Facility, Mechanical Ventilation, Enclosed Parking Garage, International Building Code