[Equest-users] Fwd: Re: [Bldg-sim] usgbc response to outdoor air question
gems at spiritone.com
Mon Oct 17 11:09:32 PDT 2011
-------- Original Message --------
Subject: Re: [Bldg-sim] usgbc response to outdoor air question
Date: Mon, 17 Oct 2011 11:08:03 -0700
From: Carol Gardner <gems at spiritone.com>
To: Patrick J. O'Leary, Jr. <poleary1969 at gmail.com>
CC: bldg-sim at lists.onebuilding.org
Chances are they don't have a "straight answer" to give you. I would
recommend modeling it the way that feels right to you, using your
knowledge of how the building works and your expertise as a modeler, and
providing documentation for the choices you made and why you believe
they are correct. If your arguments hold together you might not have any
trouble at all.
On 10/17/2011 10:37 AM, Patrick J. O'Leary, Jr. wrote:
> you're welcome james. now if i could only get a straight answer on
> how to address baseline system sizing/outdoor air rates when the
> proposed building is evaporatively cooled with 100% outdoor air ....
> sizing a baseline building system of packaged dx just doesn't sit
> right when the proposed is providing 20,000 cfm with 100% outdoor
> air. and i get mixed comments from reviewers about too much energy
> savings ... or providing too much outdoor air in the baseline ...
> On 10/17/11 9:31 AM, Jim Dirkes wrote:
>> 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] *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.
>> [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: *
>> 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 (phone)
>> 202 828-5110 (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:
>> 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
>> 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
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