[Bldg-sim] usgbc response to outdoor air question

Dennis Knight dknight at wholebuildingsystems.com
Thu Sep 19 14:47:19 PDT 2013


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> 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 ®BD&C
> 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:* Kevin Kyte [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; '
> bldg-sim at lists.onebuilding.org'
> *Cc:* '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 <Rschaber at PHMECH.com>]
> *Sent:* Tuesday, November 15, 2011 9:42 PM
> *To:* Jim Dirkes; equest-users at lists.onebuilding.org; '
> 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<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; '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
> J.****
>
> 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****
>
> ** **
>
> *From:* bldg-sim-bounces at lists.onebuilding.org [
> mailto:bldg-sim-bounces at lists.onebuilding.org<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; 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> <no-reply at gbci.org>
> <no-reply at gbci.org> <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/contactusand 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 (phone)
> 202 828-5110 (fax)
> 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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-- 
M. Dennis Knight, P.E., FASHRAE
Founder & CEO
*W*hole *B*uilding *S*ystems, LLC
P.O. Box 1845
Mt. Pleasant, SC 29465
Phone: 843-437-3647
Email: dknight at wholebuildingsystems.com
Website: www.wholebuildingsystems.com
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