[Equest-users] [Bldg-sim] usgbc response to outdoor air question

[Christopher Schaffner]

Two quick thoughts:
1. Benefits of increased ventilation: There are actually several studies
that have concluded that increased ventilation rates provide benefits. Here
is  a link to two:  http://eetd.lbl.gov/news-archives/news-ventilation.html
2. While LEED 2009 and ASHRAE 90.1-2007 (Appendix G) require identical
ventilation rates, that will change with 90.-2010 and LEED 2012.  So in LEED
2012, if you take the increased ventilation path, you'll be required to
model the potential energy impact.

--

Chris Schaffner, PE
LEED Fellow
Founder and Principal

The Green Engineer, LLP
Sustainable Design Consulting
50 Beharrell Street
Concord, MA 01742
T: 978.369.8978
M:978.844.1464
chris at greenengineer.com
www.greenengineer.com

The Green Engineer, LLP is a Certified B Corporation

From:  Jim Dirkes <jim at buildingperformanceteam.com>
Date:  Mon, 17 Oct 2011 12:31:40 -0400
To:  <equest-users at lists.onebuilding.org>,
"'bldg-sim 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 won¹t admit that I¹ve 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 ³IEQ vs. energy²; 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 can¹t 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, I¹m smarter than I was as a result of your post, so it¹s 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.

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 (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:
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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