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NC-2009 IEQp1:Minimum IAQ Performance

Increasing Space Ventilation Efficiency by Increasing Vpz

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Ed Floyd
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Question seems to simple to me but I can not find a definate answer. Is it acceptable / Common to increase the primary air flow to a critical zone to increase the over system ventilation efficiency? I have a typical office building with typical zones. Of course conferance & board rooms are causing the Ev to plumit (around the .275 range). Will LEED Reviewers allow me to model the baseline as is with the design primary air flow rate and model the proposed with and increase supply to my critical zones to get my Ev closer to 1.0? The small amount of fan power and possible reheat required will be far less then the over ventilation.

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Thu, 01/24/2013 - 23:19

The ASHRAE tool created for use with Standard 62.1 was intended to be a design tool, not a compliance tool. To use the tool correctly you should adjust the airflows to zone from a specific system until zone EV values are reasonable similar. You can also reduce the specific system OA to "optimize" the ventilation. For all the projects I work one if the zone Ev are very dissimilar I try to get the design engineers to make adjustments. The simplest adjustment, particularly if a something is already built, is to divert ventilation air from a high Ev zone to a lower EV zone. In terms of adjusting TAB that is the easiest and lowest impact. The OA setting doesn't have to to change, in many cases. For projects where the Reviewers have doubted the accuracy of the ventilation calculations, I have redone the calculations for the engineers, had the owner make some ventilation adjustments, get a amended TAB to make the changes, and submitted the TAB along with the owner's amendment for LEED review.
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Ed Floyd
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Fri, 01/25/2013 - 00:31

Hernando, Thank you for the quick response. I was not very clear in the wording of the question. I will add some details if I may. Location: Detroit Michigan Equipment: Water cooled DX and gas heat packaged roof tops Interior Zones: VAV Perimeter Zones: Fan powered VAV with electric heat Demand control ventilation in the densly occupied spaces and CO2 sensors in the roof top units I was denied some energy credits because my baseline outside air quantities did not match my proposed numbers. This is due to me running the calculations in the proposed systems and increasing the primary minimums to the critical spaces until I got to a very good Ev. I left the baseline with minmum air flows to all zones. This really leans the model in my favor. I guess my question is: In LEED's eyes is it incumbant on me to model the baseline with increased primary supply air to critical zones if I have done the same in my proposed model? Thank you again for the insight, Edward.

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