[Bldg-sim] ASHRAE 62.1

RobertWichert robert at wichert.org
Fri Mar 27 20:51:43 PDT 2009


Thanks David,

I have learned a lot since I first posted on this topic.

Peter Moberg was nice enough to provide great information and a 
spreadsheet from 62.1: 2004.  I also bought the User's Guide for 62.1: 
2007.  In it there was a spreadsheet that, although it was difficult for 
me to decipher originally, gave a great tool for solving this dilemma.

I had already developed my own spreadsheet, which was much more 
rudimentary than the ASHRAE spreadsheet.  Although my spreadsheet wasn't 
up to snuff, it helped me to understand the issue and to enter the data.

I am still not done with the analysis, but I do believe the I am well on 
my way to understanding the issue and providing a solution.  You are 
quite correct, once the critical zone is identified, changes can be made 
to effect a solution


Thanks for helping me to understand this issue,



-- 
Robert P. Wichert, P.Eng.
+1 916 966 9060
FAX +1 916 966 9068




================================================





David Yuill wrote:

>Robert,
>
>I haven't seen any replies to your Std. 62.1 question, so I'll assume you're
>still wondering.  
>
>The standard calculation of the required outdoor air (OA) amount already
>includes population diversity, which typically reduces the total OA
>required.  So, to your question:  yes, diversity can be used to reduce
>system OA requirements (and is a normal part of the Std. 62.1 calculation).
>Diversity is calculated with equation 6-7, and it's factored into the total
>uncorrected OA intake amount in equation 6-6 (referencing 62.1-2007).
>
>If you're correctly using the standard for a system that serves multiple
>zones and uses some recirculated air, you will have calculated which zone is
>the critical zone: the that zone needs the greatest fraction of primary air
>at the ventilation design condition.  (Note that the ventilation design
>condition is not the cooling or heating design condition, necessarily).  The
>critical zone drives the total OA requirement.  All other zones
>automatically get the required OA allotment or more.  
>
>To know which zone is the critical zone, look at Appendix A.  There's a
>section called "Selecting Zones for Calculation".
>
>To your comment "every room with only one person gets the required OA
>allotment", note that every zone has a population AND an area component to
>the required OA.  
>
>There are ways to meet the standard and reduce the total OA required.  These
>generally involve changing the critical zone until it becomes non-critical
>(the next most ventilation intensive zone becomes the critical zone).  This
>can be done with a transfer air fan (bringing air from an over-ventilated
>zone to reduce the required primary air in the critical zone), or by
>increasing the minimum VAV flow setting on the critical zone (this zone may
>use more reheat energy, but this can be offset by the cooling energy saved
>by reducing the total OA, for example).  It depends on your particular case.
>
>If that doesn't answer your questions, feel free to email me off-list.
>
>
>
>David Yuill, P.E.
>Principal
>==================
>Building Solutions, Inc.
>3315 S. 96th Street
>Omaha, NE 68124
>402-556-3382
>bsiengineering.com
>==================
>
>-----Original Message-----
>From: bldg-sim-bounces at lists.onebuilding.org
>[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of RobertWichert
>Sent: Wednesday, March 25, 2009 2:24 PM
>Cc: bldg-sim at lists.onebuilding.org
>Subject: [Bldg-sim] ASHRAE 62.1
>
>
>I posted an ASHRAE 62.1 question to this list a few days ago.  I have 
>made a lot of progress since then, but there are still a few nagging 
>questions.  I know that ASHRAE 62.1 is not a primary focus of this list, 
>but I hope that some of you LEED gurus out there will help me out.
>
>Basically I am looking to find out if population diversity can be used, 
>across the board, to reduce the system outside air requirements in 62.1 
>and if you can do that, how do you document room-by-room compliance as 
>required by LEED Existing Building requirements?  My thoughts right now 
>are to use population diversity to reduce the entire system OA 
>requirement, but to check that every room with only one person gets the 
>required OA allotment.
>
>This is perhaps more strict than necessary.
>
>All ideas are welcome, but if somebody is an ASHRAE 62.2 guru, I 'd love 
>to correspond off-list on this.
>
>Cheers!
>
> 
>
>  
>





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