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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.<br>
<br>
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.<br>
<br>
regards,<br>
patrick<br>
<p>[Fwd: Case 00531150: General LEED Questions</p>
<p>-------- Original Message --------</p>
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<p>Case 00531150: General LEED Questions [
ref:00D49UeD.5004GN692:ref ]</p>
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<th align="right" nowrap="nowrap" valign="baseline">Date: </th>
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<p>Mon, 17 Oct 2011 06:54:51 +0000 (GMT)</p>
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<th align="right" nowrap="nowrap" valign="baseline">From: </th>
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<p>"No reply GBCI" <a moz-do-not-send="true"
class="moz-txt-link-rfc2396E"
href="mailto:no-reply@gbci.org"><no-reply@gbci.org></a>
<a moz-do-not-send="true" class="moz-txt-link-rfc2396E"
href="mailto:no-reply@gbci.org"><no-reply@gbci.org></a></p>
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<p>patrick@<br>
</p>
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<p><br>
</p>
Dear Patrick,<br>
<br>
Thank you for contacting the Green Building Certification Institute.
<br>
<br>
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.<br>
<br>
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.<br>
<br>
The following generic LEED Review Comment applies to ventilation
systems that do not have demand controlled ventilation:<br>
<br>
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).<br>
<br>
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. <br>
<br>
The following generic LEED Review Comment applies to ventilation
systems that do have demand controlled ventilation:<br>
<br>
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).<br>
<br>
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. <br>
<br>
The following generic LEED Review Comment addresses energy recovery
in
EAc1 energy models as it relates to ventilation systems.<br>
<br>
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.
<br>
<br>
I hope that helps, but if you have any further questions or
concerns,
please feel free to use the contact form at
<a moz-do-not-send="true" class="moz-txt-link-freetext"
href="http://www.gbci.org/contactus">http://www.gbci.org/contactus</a>
and select "Follow up to GBCI Response,"
inputting your case number from this email's subject line.<br>
<br>
Best Regards,<br>
<br>
Dan Katzenberger, P.E., CEM, BEMP, LEED-AP BD+C<br>
<br>
Green Building Certification Institute <br>
2101 L Street NW, Suite 500 <br>
Washington, DC 20037 <br>
800-795-1746 (phone)<br>
202 828-5110 (fax) <br>
<a moz-do-not-send="true" class="moz-txt-link-abbreviated"
href="http://www.gbci.org/contactus">www.gbci.org/contactus</a><br>
<br>
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.<br>
<br>
<br>
_______________________________<br>
CUSTOMER EMAIL ADDRESS: <br>
patirck@<br>
<br>
CUSTOMER INQUIRY:<br>
I am trying to verify what the minimum outdoor airflow rate required
for EAc1 is and am not sure if this requires a CIR. <br>
<br>
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. <br>
<br>
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? <br>
<br>
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. <br>
<br>
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. <br>
<br>
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.
<br>
<br>
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.<br>
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