ASHRAE Ventilation Standard 62.1
The ASHRAE (American Society of Heating, Refrigerating, and Air Conditioning) Standard 62.1 is a design guide that is used to improve indoor air quality conditions inside buildings by specifying minimum ventilation and exhaust rates in order to provide acceptable air quality that minimizes harmful health effects for building occupants.
Standard 62.1´s minimum ventilation rates vary per occupancy category and is defined by the outdoor air flow rate in cubic feet per minute (CFM) that is required in a particular space. The amount of CFM of outdoor air in a space is defined by the amount of people in a space plus the area of the space. For example, the required amount of outdoor air for an office space is 5 CFM per person plus 0.06 CFM per feet squared (ft2) of area. So if an office space is 500 ft2 and it is designed to have an occupancy of 20 people, then the required ventilation rate for that space is (5 CFM/person x 20 people) + (0.06 CFM/ ft2 x 500 ft2) = 100 CFM + 30 CFM = 130 CFM total of ventilation or outdoor air that is required for that space.
ASHRAE 62.1 and LEED
If you are designing a system to achieve LEED points for the credit that deals with ventilation rates, then you have to surpass ventilation rates by 30% at the system level. This means that you have to sum up the ventilation rates for each space in a particular system. The system would most likely be an air handler. If the outdoor air that is supplied to an air handler by design is 30% or more than the sum of the ventilation rates required by ASHRAE 62.1 for each space, then the system complies and the project will get points for this credit. It should be noted that it is mandatory for projects to meet at least the minimum ventilation requires listed in ASHRAE 62.1 to be even considered forLEED certification. The US Green Building Council has an ASHRAE 62.1 user´s manual that is available as a free download once a project has registered for LEED.