I have a wine tasting room space that utilizes mechanical ventilation (with ERV units) for most of the year. In spring and fall weekend use, the occupant load increases and natural ventilation is utilized to meet fresh air requirements. I see that mixed mode ventilation must still be calculated to meet the chapter 6, ASHRAE 62.1-2007 requirements, using the VRP calculattions. How do you include natural ventilation in the VRP calculations? Is there a way to convert the operable window area to occupiable area ratio (used in the Chapter 5, natural ventilation section of ASHRAE 62.1-2007) to an estimate of CFM of air flow to use in the calculations?
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Roger Chang
Principal, Energy and Engineering LeaderDLR Group | Westlake Reed Leskosky
LEEDuser Expert
398 thumbs up
November 30, 2012 - 9:57 am
Thomas, if the mechanical ventilation system meets ASHRAE 62.1 requirements, base the VRP calculations for LEED on that system. To represent the natural ventilation mode, you'll want to comply with the open area requirements specified in the Natural Ventilation portion of ASHRAE 62.1.
Tom O'Neil
architectO'Neil Architects, Inc.
1 thumbs up
December 2, 2012 - 12:42 pm
Roger, When the tasting room if fully occupied during a few hours of the afternoon on weekends, the mechanical ventilation system does not meet the ASHRAE 62.1 requirements. That is when it was intended for natural ventilation to be used to replace or supplement the mechaninacal ventilation, thus the "mixed mode". The natural venitalation does meet the requirements of the Natural Ventilation portion of 62.1, but the reviewer said that if we had both systems in the same space, it is considered "mixed mode" and must follow the requirements of the mechanical ventilation requirements of 62.1. That is why I was asking if there was some way of converting or estimating natural ventilation intake amounts to use in the VRP calculations. Or, is the reviewer telling me that when using "mixed mode" I must meet the ventilation requirements with only the mechanical ventilation? This would seem to defeat the purpose of providing natural ventilation during the limited times that it is needed, and force me to increase the size of the ERV units or introduce another mechanical outside air source..
Roger Chang
Principal, Energy and Engineering LeaderDLR Group | Westlake Reed Leskosky
LEEDuser Expert
398 thumbs up
January 5, 2013 - 10:50 am
Tom, there's not a good way to convert airflow from a natural ventilation scheme to a mechanical ventilation equivalent in a way intended for compliance with ASHRAE 62. Could you expand upon the fully occupied situation you mentioned that occurs on the weekends? There are other approaches to reduce the mechanical ventilation rates you use, based on the short-term averaging provisions of ASHRAE 62. The main issue here is that there is still the potential for the mechanical ventilation system to be used in lieu of the natural ventilation system during a weekend event?
Tom O'Neil
architectO'Neil Architects, Inc.
1 thumbs up
January 14, 2013 - 2:31 pm
Roger, The fully occupied period is 1-5 pm on Saturdays and Sundays. The space is open from 11 am to 6 pm Wednesday through Monday. Fully occupied is approximately 70 visitors and four employees in the tasting room. All other open times it averages about 12 visitors and two employees. How do I calculate short term averaging? There is a mechanical ventilation system in place that could be used instead of the natural ventilation system, although currently it does not have the capacity for the peak load periods. Thanks.
Tom O'Neil
architectO'Neil Architects, Inc.
1 thumbs up
February 12, 2013 - 9:05 am
Roger,
I have looked at ASHRAE 62.1, section 6.2.6.2, Short Term Conditions, and can't figure out how to apply the formulas they have listed for short term averaging. Have you dealt with these before and can you describe how to use them properly? Thank you.