[Hap-users] LEED requirement for Baseline Ventilation matchingProposed Ventilation

Reba Schaber Rschaber at PHMECH.com
Thu Nov 1 18:55:09 PDT 2012


Using ASHRAE ventilation sizing will find the critical space and correct the outdoor air accordingly.  The supply air affects this calculation.  Sum of the spaces simply adds the outdoor air requirement for each space.  I don't think the space supply air matters for this.

I use the USGBC LEED 62MZCalc excel spreadsheet and calculate the required OSA based on my proposed design.  USGBC likes to see this spreadsheet, especially if I'm going for the increased ventilation credit.  Then I enter the ventilation at the space level as a user defined cfm.  Since the spreadsheet has already calculated the critical space, in the system I use Sum of Spaces OA airflows.  When I create the Baseline system, the user-defined ventilation remains the same in the baseline space.

It's a little more work up front.  The corrected OSA, as calculated by the spreadsheet, is always greater than the sum of the spaces.  So the space ventilation has to be proportionally increased.  But it's convenient when the baseline systems are different from the proposed system.   Like when my proposed VAV air handler with 20 VAV boxes turns into 20 baseline package rooftop units.

I have one question for the Carrier techs.  I understand that when calculating the space supply air, HAP will never go below the required ventilation airflow.  So when a ventilation rate is entered at the system with the user-defined sizing, how does HAP make sure the space supply air is always greater than the ventilation requirement for each space?

                 PH MECHANICAL ENGINEERING
         Reba Schaber      Mechanical Engineer, P.E.
                                     LEED Accredited Professional
1660 N. Alvernon Way                Voice: (520) 731-2060
Tucson, Arizona 85712                Fax: (520) 731-2061
                        rschaber at phmech.com<mailto:rschaber at phmech.com>

From: hap-users-bounces at lists.onebuilding.org [mailto:hap-users-bounces at lists.onebuilding.org] On Behalf Of Matthew Scott
Sent: Thursday, November 01, 2012 3:43 PM
To: Systems, Software CCS
Cc: hap-users at lists.onebuilding.org; nef mail
Subject: Re: [Hap-users] LEED requirement for Baseline Ventilation matchingProposed Ventilation

I was hoping there was a more elegant way to do it, but ok.

Just to clarify, in the "first run" of the Baseline system to size the supply CFM, should the "ventilation sizing method" be set to ASHRAE-2007 or Sum of Spaces or does it matter? I have a feeling the calculated supply CFM could be influenced by the ventilation calculation.

Thanks for your help. I have used the tech support extensively; just wanted to get some feedback from other users.

Matt Scott
N.E. Fisher & Associates, Inc.
329 East Second St, 2nd Flr
Boyertown, PA 19512
e: mscott at nefisher.com<mailto:mscott at nefisher.com>
p: 610-369-3190
f: 610-369-3194

From: Systems, Software CCS [mailto:Software.Systems at carrier.utc.com]
Sent: Thursday, November 01, 2012 6:15 PM
To: Matthew Scott
Subject: RE: [Hap-users] LEED requirement for Baseline Ventilation matchingProposed Ventilation

Matt,

The approach you describe is the correct procedure.

Also, please not that as a HAP software licensee you and your firm can get answers to questions like these from the Carrier software help desk by e-mailing software.systems at carrier.utc.com<mailto:software.systems at carrier.utc.com>

Best Regards,

Jim Pegues
Carrier Software Systems

From: hap-users-bounces at lists.onebuilding.org<mailto:hap-users-bounces at lists.onebuilding.org> [mailto:hap-users-bounces at lists.onebuilding.org] On Behalf Of Matthew Scott
Sent: Thursday, November 01, 2012 5:50 PM
To: hap-users at lists.onebuilding.org<mailto:hap-users at lists.onebuilding.org>
Cc: nef mail
Subject: [Hap-users] LEED requirement for Baseline Ventilation matching Proposed Ventilation

What is the proper way in HAP to get your Baseline model to use the exact same amount of ventilation air as your proposed model when LEED requires that HAP auto-calculate the supply CFM based on a 20 degree rise?

Do you run the simulation once with the 20 degree rise to calculate your supply CFM. Then switch to User-Defined Sizing mode and input the Proposed ventilation CFM and the supply CFM that was calculated in the first run?

Matt Scott
N.E. Fisher & Associates, Inc.
329 East Second St, 2nd Flr
Boyertown, PA 19512
e: mscott at nefisher.com<mailto:mscott at nefisher.com>
p: 610-369-3190
f: 610-369-3194

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