[Bldg-sim] How to Model Parkade CO2 Levels for Exhaust Requirements

Dónal O'Connor oconnor_dj at hotmail.com
Wed Nov 28 10:03:53 PST 2012

Hi all,

Thanks for all of your responses! They're greatly appreciated!



From: Paul.Riemer at dunhameng.com
To: fbetz at aeieng.com; bquitadamo at RDKEngineers.com; oconnor_dj at hotmail.com; bldg-sim at lists.onebuilding.org
Date: Wed, 28 Nov 2012 11:42:21 -0600
Subject: RE: [Bldg-sim] How to Model Parkade CO2 Levels for	Exhaust	Requirements

Donal,We have discussed this previously so I suggest reviewing both the Bldg-Sim and equest-users archives.  I vaguely recalled posts about GBCI pushing back on crediting CO-based control, so I found one and pasted it below. As for ‘while it lasts’ - if addendum bm succeeds in rolling Appendix G back to align with 90.1-2004 then it seems like CO-based control of garage fans could be back in play as we simulate to demonstrate 40%-50%-60%-? savings vs. 90.1-2004 baseline. Paul Riemer, PE, LEED AP BD+C DUNHAM  -----Original Message-----From: James Hansen [mailto:JHANSEN at ghtltd.com] Sent: Tuesday, August 02, 2011 10:08 AMTo: Nick Caton; Ömer Moltay; equest-users at lists.onebuilding.orgSubject: RE: [Equest-users] Modelling Parking Garage Exhaust Combined withJetFans Please also note that if this is for a LEED project, one of the "default" review comments now for CO-based control of garage fans is that the design professional must demonstrate that this is not a "standard practice" for new base-building projects in the area.  I personally think this is a ridiculous comment, but regardless, be prepared to provide a list of new projects in the area that you've worked on that have not had CO-based control of the parking garage fans, otherwise you might have to include it in both the baseline and proposed models.  I would love to hear how other people have addressed this comment. GHT LimitedJames Hansen, P.E., LEED AP  From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Fred Betz
Sent: Wednesday, November 28, 2012 9:02 AM
To: Quitadamo, Bob; Dónal O'Connor; Building Sim Forum
Subject: Re: [Bldg-sim] How to Model Parkade CO2 Levels for Exhaust Requirements Donal, Yes, the fans are controlled based on CO, not CO2.  You would just create different schedules for the exhaust. The baseline is constant flow during the occupied hours plus 1 hr before and after occupancy to capture people arriving early and leaving late. ASHRAE 62.1 requires 0.75 cfm/ft2 of outside air flow. You’ll have to determine what flow rate your local code requires.  For the proposed model, create a new air flow schedule that gets you approximately 80-95% energy savings. There are several reports online that provide these ranges. Look for the ones from building owners or researchers, not manufacturers that claim 98-99% savings. The 80-95% range is based on a number of studies of these systems, as the fans spend most of their time at minimum flow, ~0.15 cfm/ft2. In general, if the building operates many hours you’ll be closer to 95%, and 80% if the building operates few hours. I like to create a profile so I capture demand charges properly rather than a flat average curve. For an office space, you’d have peaks from 7-9, a bump from 12-1 for those people going out to lunch, and another peak from 4-6 as people go home. For a hospital parking garage I just modeled, I had peaks from 11pm - 1am, 7-8am, and 4-6pm to capture shift changes. You’ll have to decide what makes sense for your specific project.  Hope that makes sense.  Fred  P.S. CO demand control ventilation will be included in the Baseline model for ASHRAE 90.1-2010 per section Enclosed Parking Garage Ventilation. Enjoy the model savings while it lasts!  Fred Betz  PhD., LEED AP 
Sustainable Systems Analyst AEI | AFFILIATED ENGINEERS, INC.  
5802 Research Park Blvd. | Madison, WI  53719

P: 608.236.1175 | F: 608.238.2614  
fbetz at aeieng.com  |  www.aeieng.com    From: Quitadamo, Bob [mailto:bquitadamo at RDKEngineers.com] 
Sent: Tuesday, November 27, 2012 2:46 PM
To: Dónal O'Connor; Building Sim Forum
Subject: Re: [Bldg-sim] How to Model Parkade CO2 Levels for Exhaust Requirements Hi Donal, You’ll want to control outside air off CO (not CO2) in a parking garage and be sure the controls sequence utilize the correct ppm setpoints.  Generally there is a minimum ventilation/exhaust rate to maintain even when CO levels are in check for code compliance.  For modeling the system, a specific ventilation schedule correlating to expected usage of the car garage has worked for me in the past.  I would imagine similar schedules for this facility have been created for occupancy and lighting/plug loads. Regards, Bob Quitadamo  From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Dónal O'Connor
Sent: Tuesday, November 27, 2012 9:55 AM
To: Building Sim Forum
Subject: [Bldg-sim] How to Model Parkade CO2 Levels for Exhaust Requirements Dear building-sim,I'm currently working on a LEED NC sports facility with an underground parkade for approximately 200 cars.The parkade exhaust system (100% OA) turns on if the CO2 levels detected in the parkade exceed a particular threshold. Has anybody modeled such a system? What assumptions can be made for the CO2 profile? As it is in a northern climate, I do not want to overestimate the usage of the system which would skew the heating energy required to heat the OA to the required supply temperature.Your help is greatly appreciated.ThanksDonal 		 	   		  
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