ventilation rate according 62.1

Marco Abdallah

LEEDuser Basic Member

24 thumbs up

February 25, 2014

Dear LEED Team, just calculated the ventilation rate according the ashrae 62.1.2007 for a office building and now really wonder about the low outdoor air rate: Density: 100 ft²/person (net occupiable area in zone) OA per person: 5 cfm OA per m²: 0,6 cfm/ft² Combined OA per person: 5 cfm + 0,06 cfm/ft² x 100 ft² = 11 cfm/person Compared to the European standard with around 20 cfm this seems to be very less. In cubicle offices with lower density it even gets worse. At the same time the ASHRAE recommends a CO2 level of 1000ppm - which is not reachable with the given 11 cfm/person. So, how can this be explained?

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Julia Weatherby

President

Weatherby Design & Co. Engineers

LEEDuser Basic Member

67 thumbs up

Wed, 03/12/2014 - 14:27

Hello- Although still widely cited, the 1,000 ppm CO2 concentration is an old ASHRAE reference from 62.1-1989. I don't believe 62.1-2007 refers to that CO2 level. ASHRAE has converted to a dual component method of recommended minimum ventilation rates, based on air flow per unit area plus air flow per person. Apparently, the new ventilation rates recommended are considered adequate even though they can result in CO2 concentrations well above 1000 ppm.

Dave Hubka

Practice Leader - Sustainability

EUA

LEEDuser Expert

510 thumbs up

Wed, 03/12/2014 - 14:45

Marco, you calculated Vbz, but you need to calculate Vot to determine how much OA is needed for compliance.

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