[Bldg-rate] [Bldg-sim] usgbc response to outdoor air question
Bill Talbert
btalbert at aeieng.com
Fri Sep 20 09:20:26 PDT 2013
Dennis,
Attached is an interpretation from ASHRAE indicating the area based ventilation rate cannot be turned off during unoccupied hours (applicable to 2007 and 2010). Subsequently, ASHRAE is in the process of issuing an addendum that does allow the area based rate to be turned off based on occupancy controls. The addendum (also attached) went out for public review last spring. I don't see that it has been published on the ASHRAE website yet, so I'm not sure whether it has been fully approved by the committee yet.
Also, in my experience, LEED (v2009) requires that the baseline ventilation rate comply with the ASHRAE 62.1 minimum when DCV controls are implemented in the proposed design for spaces not required to have it per 90.1. This would be the only scenario where baseline ventilation rates differ from the proposed (i.e. no energy penalty for over ventilating). This changes for LEED v4 which used 90.1-2010.
Regards,
Bill
Bill Talbert PE, LEED(r) BD+C
Sustainable
AEI | AFFILIATED ENGINEERS, INC.
5802 Research Park Boulevard | Madison, WI 53719
P: 608.441.6677 | C: 608.234.3803 | F: 608.238.2614
btalbert at aeieng.com<mailto:btalbert at aeieng.com> | www.aeieng.com<http://www.aeieng.com/>
From: bldg-rate-bounces at lists.onebuilding.org [mailto:bldg-rate-bounces at lists.onebuilding.org] On Behalf Of Mike Karpman
Sent: Friday, September 20, 2013 11:00 AM
To: Dennis Knight; Fred Betz
Cc: equest-users at lists.onebuilding.org; bldg-sim at lists.onebuilding.org; bldg-rate at lists.onebuilding.org
Subject: Re: [Bldg-rate] [Bldg-sim] usgbc response to outdoor air question
Hello All,
Please see the following relevant quote from 62.1 2010:
[cid:image001.jpg at 01CEB5F2.A52AED10]
To me this implies that all of the requirements in section 6 (which include both the area and occupant components) are only applicable "when [spaces] are expected to be occupied".
Regards,
Mike
From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> [mailto:bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org>] On Behalf Of Dennis Knight
Sent: Thursday, September 19, 2013 5:47 PM
To: Fred Betz
Cc: Kevin Kyte; bldg-rate at lists.onebuilding.org<mailto:bldg-rate at lists.onebuilding.org>; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>; bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: Re: [Bldg-sim] usgbc response to outdoor air question
ASHRAE 62.1-2010 may be viewed online for free from the ASHRAE website at: https://www.ashrae.org/standards-research--technology/standards--guidelines. Its a little slow and painful to view and navigate since it is a free.
Also, all approved addenda may be downloaded in PDF from here: https://www.ashrae.org/standards-research--technology/standards-addenda.
I reviewed both documents and did not see any rulings, interpretations or addenda that would indicate that the area based portion of the ventilation rate is required to operate 24/7 or during unoccupied periods. If anyone has a better resource than this please post.
Thanks,
Dennis
On Thu, Sep 19, 2013 at 4:34 PM, Fred Betz <fbetz at aeieng.com<mailto:fbetz at aeieng.com>> wrote:
My understanding is that for a 90.1-2007 outside air is modeled at the same CFM even if it's beyond ASHRAE 62.1 requirements with no energy penalty. However, this is no longer true in 90.1-2010 where the baseline is to follow ASRAE 62.1.
Also, I thought there was a ruling or interpretation to 62.1 that only allowed the elimination of the occupant portion of the ventilation to be shut off during unoccupied hours, but the area based outside air needs to be maintained at night to handle off-gassing. I believe the 90.1 folks are still discussing how to incorporate this ruling into the standard.
If you don't have more DCV than the baseline, just use show in a calculation the total CFM and fraction of outside air for each AHU and show them the total is approximately the same. There is some latitude here for rounding errors and the like as some complex buildings may be off by a few percent. If your proposed outside cfm is slightly greater than your baseline outside cfm, then you should definitely be ok as your model will be conservative.
Hope that helps,
Fred
Fred Betz PhD., LEED AP (r)BD&C
Sustainable Systems Analyst
AEI | AFFILIATED ENGINEERS, INC.
5802 Research Park Blvd. | Madison, WI 53719
P: 608.236.1175<tel:608.236.1175> | F: 608.238.2614<tel:608.238.2614>
fbetz at aeieng.com<mailto:fbetz at aeieng.com> | www.aeieng.com<http://www.aeieng.com/>
From: Kevin Kyte [mailto:KKyte at watts-ae.com<mailto:KKyte at watts-ae.com>]
Sent: Thursday, September 19, 2013 2:59 PM
To: Reba Schaber; Jim Dirkes; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>; 'bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>'
Cc: 'bldg-rate at lists.onebuilding.org<mailto:bldg-rate at lists.onebuilding.org>'
Subject: Re: [Bldg-sim] usgbc response to outdoor air question
Ok, so I received this comment. The one with the provide ASHRAE minimums in the Baseline for spaces with DCV. I understand this is a generic comment - Ok.
However, LEED IEQ Credit 2 is not being pursued and the ASHRAE minimum ventilation requirements are what is being Proposed for in each space that has DCV.
Does this not mean that the Baseline ventilation rate and the Proposed ventilation rate will still be equal?
Not sure how to respond other than to simply say what is stated here.
Thanks,
Kevin
From: Reba Schaber [mailto:Rschaber at PHMECH.com]
Sent: Tuesday, November 15, 2011 9:42 PM
To: Jim Dirkes; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>; 'bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>'
Subject: Re: [Bldg-sim] usgbc response to outdoor air question
RE: ". . . can't find) anything in 621.1 which says that unoccupied ventilation should be zero."
I think this requirement comes from the mandatory provisions of 90.1.
6.4.3.4.3 Shutoff Damper Controls. Both outdoor
air supply and exhaust systems shall be equipped with motorized
dampers that will automatically shut when the systems or
spaces served are not in use. Ventilation outdoor air dampers
shall be capable of automatically shutting off during preoccupancy
building warm-up, cool down, and setback, except
when ventilation reduces energy costs (e.g., night purge) or
when ventilation must be supplied to meet code requirements.
Thoughts??
Reba
From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Jim Dirkes
Sent: Monday, October 17, 2011 9:32 AM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>; 'bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>'
Subject: Re: [Bldg-sim] usgbc response to outdoor air question
Dear Patrick,
Thank you for sharing this GBCI response! It is very informative and, while I won't admit that I've been modeling anything incorrectly, I am going to change a couple of things :).
In particular, I have heard on several occasions that the Increased Ventilation credit was a clear case of "IEQ vs. energy"; you make a decision to trade one against the other. After reading the GBCI response below and then double-checking with ASHRAE 90.1, I find that they are consistent with each other and effectively allow no penalty for the increased energy caused by increased ventilation. Very curious, considering there is no science which demonstrates a health benefit for outdoor airflows greater than that required by ASHRAE 62.1!
The other item is that I failed to notice (and still can't find) anything in 621.1 which says that unoccupied ventilation should be zero. I guess that is OK, but is also curious, since a portion of the ventilation calcs in 62.1 include consideration for off-gassing materials (which are always present.)
All in all, I'm smarter than I was as a result of your post, so it's a good day! Thanks again.
The Building Performance Team
James V. Dirkes II, P.E., BEMP , LEED AP
1631 Acacia Drive NW
Grand Rapids, MI 49504
616 450 8653<tel:616%20450%208653>
From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Patrick J. O'Leary, Jr.
Sent: Monday, October 17, 2011 11:46 AM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>; bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>
Subject: [Bldg-sim] usgbc response to outdoor air question
back in september there was a thread about what the outdoor air rate in a baseline simulation should be compared to a proposed simulation, specifically when one is adding 30% more outdoor air to meet the ieqc2 requirement and earn 1 leed point. there were differences of opinions about the flow rates between baseline and proposed being either the same (as required in 90.1 app g) or the baseline being the calculated per 62.1 and the proposed being as designed.
so i submitted a support request to the usgbc and the reply i received is below, but in short the response is that unless you're using dcv optionally the outdoor air rates in the baseline and proposed energy simulations for eac1 should be the same. the response below gives the standard responses to differing outdoor air rate scenarios.
regards,
patrick
[Fwd: Case 00531150: General LEED Questions
-------- Original Message --------
Subject:
Case 00531150: General LEED Questions [ ref:00D49UeD.5004GN692:ref ]
Date:
Mon, 17 Oct 2011 06:54:51 +0000 (GMT)
From:
"No reply GBCI" <no-reply at gbci.org><mailto:no-reply at gbci.org> <no-reply at gbci.org><mailto:no-reply at gbci.org>
To:
patrick@
Dear Patrick,
Thank you for contacting the Green Building Certification Institute.
You ask very good questions related to the relationship between ASHRAE Standards 62.1 and 90.1, and how these standards are applied across multiple LEED Rating System prerequisites and credits.
The simple answer to your question is that, for systems without demand controlled ventilation, the outdoor air included in EA Credit 1 energy simulations must be the same in the Baseline and Proposed cases. If the project is attempting IEQ Credit 2 Increased Ventilation, then the values calculated in IEQc2 must be used in the EAc1 Basline and Proposed case energy models. Note that IEQc2 does not limit the project to providing only 30% more outdoor air than AHRAE 62.1 Ventilation Rate Procedure minimums, so higher amounts are acceptable, as long as they are modeled identically in both the Baseline and Proposed case energy models.
The following generic LEED Review Comment applies to ventilation systems that do not have demand controlled ventilation:
It is unclear whether the minimum outside air rates (in CFM) were modeled identically in the Baseline and Proposed case for all zones not having Demand Control Ventilation in the Proposed case. Please confirm that minimum outside airflow (in units of cfm) was modeled identically in the Baseline and Proposed cases using the proposed case rates. Additionally, please verify that all systems in both the baseline and proposed case are modeled with zero outside air flow when fans are cycled on to meet unoccupied setback temperatures unless health or safety regulations mandate an alternate minimum flow during unoccupied periods (in which case, the unoccupied outside air rates should be modeled identically in the Baseline and Proposed case).
The situation becomes a bit more complicated in you have systems that have demand controlled ventilation (often implemented as Carbon Dioxide control of outdoor air or as programmed control of outdoor air based on occupancy sensors.) In this case the Baseline case energy model must include the minimum outdoor air as determined by the ASHRAE 62.1 Ventilation Rate Procedure calculations for all systems having demand controlled ventilation.
The following generic LEED Review Comment applies to ventilation systems that do have demand controlled ventilation:
Demand control ventilation was modeled for credit in the proposed case. Appendix G allows schedule changes for demand control ventilation as approved by the rating authority (Table G3.1#4(Baseline)). As the LEED Certification rating authority, GBCI requires that the outside air ventilation rates for the Baseline case be modeled using minimum ASHRAE 62.1-2004 (or 2007 for LEED-NC 2009 projects) rates wherever credit is taken for demand control ventilation in the Proposed case. The proposed case minimum rates at design conditions should be modeled as designed. Please verify that the Baseline Case model reflects ASHRAE 62.1-2004 (or 2007) minimum rates for any spaces where credit is taken for demand control ventilation, or revise the model accordingly. For all other spaces, please confirm that minimum outside airflow (in units of cfm) was modeled identically in the Baseline and Proposed cases. Additionally, please verify that all systems in both the baseline and proposed cases are modeled with zero outside air flow when fans are cycled on to meet unoccupied setback temperatures unless health or safety regulations mandate an alternate minimum flow during unoccupied periods (in which case, the unoccupied outside air rates should be modeled identically in the Baseline and Proposed case).
Finally, even though you don't address energy recovery in your question, whether or not you have energy recovery in your ventilation systems may affect how much better (or worse) your Proposed case energy models perform in relation to your Baseline case energy models.
The following generic LEED Review Comment addresses energy recovery in EAc1 energy models as it relates to ventilation systems.
Energy recovery is modeled for credit in the Proposed case. Please provide further information regarding the energy recovery efficiency, verify that outside air is modeled with zero flow in both the Baseline and Proposed cases during unoccupied periods when fans are cycled on to meet unoccupied setback temperatures unless health or safety regulations mandate an alternate minimum flow during unoccupied periods (in which case, the unoccupied outside air rates should be modeled identically in the Baseline and Proposed Case), and indicate the bypass mechanism used to bypass the energy recovery during mild conditions.
I hope that helps, but if you have any further questions or concerns, please feel free to use the contact form at http://www.gbci.org/contactus and select "Follow up to GBCI Response," inputting your case number from this email's subject line.
Best Regards,
Dan Katzenberger, P.E., CEM, BEMP, LEED-AP BD+C
Green Building Certification Institute
2101 L Street NW, Suite 500
Washington, DC 20037
800-795-1746<tel:800-795-1746> (phone)
202 828-5110<tel:202%20828-5110> (fax)
www.gbci.org/contactus<http://www.gbci.org/contactus>
The text above represents a staff opinion of a particular issue, and does NOT set any precedent to be upheld during a LEED Certification Review. For official rulings in advance of a LEED Certification Review, customers should utilize the Formal Inquiries process available in LEED Online that results in a Project Credit Interpretation Ruling (Project CIR) and possibly a LEED Interpretation (formerly CIRs or Public Rulings). Applications for LEED Certification will be thoroughly reviewed based on USGBC Member balloted and approved LEED Rating Systems, with addenda, and USGBC approved LEED Interpretations, or Project CIRs administered by GBCI, as applicable. Please note that certain inquiries submitted to USGBC are forwarded to GBCI for reply as appropriate.
_______________________________
CUSTOMER EMAIL ADDRESS:
patirck@
CUSTOMER INQUIRY:
I am trying to verify what the minimum outdoor airflow rate required for EAc1 is and am not sure if this requires a CIR.
If the Proposed outdoor air ventilation is a minimum of 30% higher than the minimum required by ASHRAE 62 in order to achieve 1 LEED point for credit IEQC2 is the Baseline outdoor air rate also 30% higher than the minimum required by ASHRAE 62? or would the Baseline outdoor air ventilation rate be the minimum outdoor air rate per ASHRAE 62 calculations.
In other words, if ASHRAE 62 requires a minimum of 1,000 CFM of outdoor air, and 1,300 CFM is provided to attain 1 LEED point via IEQC1, is the Baseline outdoor air flow rate 1,000 CFM or 1,300 CFM in the energy simulation?
90.1-2007/2004 both say the minimu m outdoor airflow rates shall be the same for both the proposed and baseline building designs, as does the user manual.
But this logic seems to reward the Proposed simulation by conditioning the additional outdoor air supplied (300 cfm in the example above) to achieve IEQC1 in the Baseline system as well as the proposed.
The logic of using the minimum required in the Baseline case is reflected in EAC1 in the equipment efficiency requirements. Baseline efficiencies are the minimum required, e.g. SEER 13 for packaged units.
It is the intent of the requirement that I am not sure is clear. Increasing the outdoor air ventilation rate increases the energy used to condition the outdoor air, so if the intent is to put the onus on Proposed design to show energy reduction/LEED compliance over the 90.1/62 requirements shouldn't the Baseline outdoor air be the minimum air flow rate per the ASHRAE 62 calculations? This puts the onus on the design team to provide a design that compensates for the increase in energy to meet IEQC2 by providing some method of processing the increase in outdoor air while still reducing energy consumption.
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