[Bldg-rate] [Bldg-sim] usgbc response to outdoor air question

Fri Sep 20 08:59:50 PDT 2013

Hello  All,

Please see the following relevant quote from 62.1 2010:

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] *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;
equest-users at lists.onebuilding.org; 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> 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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