[Bldg-sim] ASHRAE 62 30% increase as it relates to EAc1

Michael Tillou michael.tillou at gmail.com
Tue May 19 04:22:24 PDT 2009


And the whole thing gets even more complicated if you want to pursue  
this credit in combination with the credit for Outdoor Air Delivery  
Monitoring.

Not to mention the conflict of whether you do or do not have to claim  
the added energy cost in credit EA-1 associated with 30% increase in  
ventilation.

Michael Tillou, PE LEED AP
Tillou Engineering, LLC


Sent from my iPhone

On May 18, 2009, at 12:58 PM, "James Hansen" <JHANSEN at ghtltd.com> wrote:

> I’m having a tough time deciphering how the USGBC wants you to prove 
>  a 30% increase in OA (versus ASHRAE 62) for multi-zone systems, and 
>  how this impacts the energy model for the proposed building.
>
>
>
> There is a very specific way to determine the volume of outside air  
> for a multi-zone system (VPR using the 62MZCalc spreadsheet).  This  
> takes into account, among other things, room area, population,  
> supply volume, minimum primary air volume, efficiency of transfer  
> air, system efficiency, etc.  Once you understand all of the  
> variables, it’s fairly straightforward to prove compliance with EQp1 
> , and obtain the minimum OA intake volume.
>
>
>
> However, EQc2 requires a 30% increase in outside air volume for EACH  
> zone “above the minimum rates required by ASHRAE Standard 62.1-2004  
> as determined by EQ Prerequisite 1”.  Although I’ve received  
> USGBC comments before claiming that I have to prove that EACH zone h 
> as 30% more OA than required by the VPR, can anyone confirm for sure 
>  if this is the case for multi-zone systems?
>
>
>
> To give you an example:
>
>
>
> I’ve got a 33,000 square foot floor served by an AHU.  Standard offi 
> ce space with 3 or 4 conference rooms.  I’ve used the 62MZCalc sprea 
> dsheet, and determined that my AHU needs 3,800 CFM OA.  I’ve *design 
> ed* the system to provide 7,000 CFM.  Almost twice the amount of out 
> side air as needed (I have DCV in place).  However, the critical con 
> ference room doesn’t get even the minimum required OA.  It  
> doesn’t need to – that’s the whole point of the Multizone calc,  
> and a good reason to use series fan-powered terminals.
>
>
>
> Per the NCv2.2 Reference Guide, we are supposed to include the  
> actual OA volumes in the energy model, so I guess it’s important to  
> get this right, especially for those clients that request a 30% incr 
> ease.
>
>
>
> Thanks in advance,
>
>
>
> GHT Limited
> James Hansen, PE, LEED AP
>
> Senior Associate
>
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>
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>
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>
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>
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>
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