[Bldg-sim] DOAS and baseline OA

[Mark Sorensen]

Anne,

While LEED/ASHRAE 90.1 requires the ventilation rates to be the same in 
both the Baseline and Proposed systems, the calculated difference for 
the two systems is much higher than expected. Suggest taking another 
look at the calculations and confirming that the critical zone for the 
VAV system has been properly determined and whether appropriate factors 
for the zone air distribution effectiveness (Ez) and system ventilation 
efficiency (Ev) have been applied.

Mark Sorensen
Diversified Energy Services
Fruitport, Michigan
231-578-1264

On 8/16/2011 9:12 AM, Jim Dirkes wrote:
>
> Dear Anne,
>
> I'm not sure why you think the OA requirement varies by system.  I'm 
> not well versed in Standard 62, but my basic understanding is that one 
> of the calculation methods is the result of building area and number 
> of occupants.  Those are unchanged by system selection ... which is 
> why it makes sense for Appendix G to require matching volumes.
>
> *The Building Performance Team
> **James V. Dirkes II, P.E., BEMP , LEED AP
> *1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
>
> *From:*bldg-sim-bounces at lists.onebuilding.org 
> [mailto:bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Anne Juran
> *Sent:* Tuesday, August 16, 2011 8:33 AM
> *To:* bldg-sim at lists.onebuilding.org
> *Subject:* [Bldg-sim] DOAS and baseline OA
>
> I'm curious how everyone is handling the OA for Appendix G simulations 
> when using a DOAS in the proposed system.  We have a design that is 
> DOAS + FCU with a  total OA of 8,000 CFM.  When you run the OA calcs 
> for this same building with a VAV system (the baseline), the total OA 
> required to meet Standard 62 is 39,000 CFM.  This difference in OA 
> represents a significant energy savings (in climate zone 4A), yet 
> Appendix G requires the OA volumes to match.  It does not seem "fair" 
> to me that the proposed case cannot take credit for design choice when 
> it comes to OA.  I feel like Appendix G should make an exception for 
> DOAS.  Am I missing something?  Is there a way around this?  Any 
> thoughts are appreciated!
>
> Anne
>
>
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