Ventilation Rates and Technologies

What is ventilation?

Ventilation is the supply of outdoor air to a space through a ventilation system, via flow through open doors and windows, and by infiltration through the building envelope, for example, cracks in the walls and around doors and windows.

• Natural Ventilation

Is ventilation that occurs primarily through open windows and doors and by infiltration through cracks in the building envelope, such as walls, around windows and any penetration through the walls. Natural ventilation is driven by wind or pressure and/or temperature differences between inside and outside a building.

• Mechanical Ventilation

Outside air is delivered indoors typically with a fan(s), which draws air from outside and forces it through ducts to the place where occupants are located. Mechanical ventilation can exacerbate infiltration and/or exfiltration. Leaks in ducts can also increase the ventilation rate. Researchers at LBNL have developed a method of sealing ducts.

What are ventilation rates?

Ventilation rates express the flow rate of outside air brought into a building and are typically normalized by the volume of space being ventilated (air changes per hour), by the area of the floor being ventilated (cubic feet per min (cfm) per ft²) or by the number of people being served (cfm per person).

What are the ventilation rate standards and codes?

Standards and codes establish minimum ventilation rates to protect human health. An attempt is made to balance health and productivity benefits of increased ventilation with energy use.

• ASHRAE Ventilation Standard

The American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., develops standards for minimum ventilation rates for many different kinds of buildings and spaces. Municipalities and other code making organizations may use the ASHRAE Standards as guidelines for their enforceable codes. Typically the minimum ventilation rates in standards and codes specify minimum ventilation rates per person or per unit floor area that vary with the type of building or space usage.

California code requirements for the minimum ventilation rates for California buildings, see the Nonresidential Compliance Manual For California's 2005 Energy Efficiency Standards.