[Equest-users] Demand Controlled Ventilation and EA Credit 1
David Bastow
dbastow at mcclure-engineering.com
Tue Jul 27 16:35:51 PDT 2010
Below is some discussion that we had on the same subject month's ago.
Normally the base model, I set up with the min. percentage amount of OSA
coming in through the air side (air handler) required by code during all
occupied hours and then with this OSA closed by schedule during
unoccupied hours. Typically this is what is required by code (usually
15-20 CFM per person for all occupants), unless you have a CO2 demand
control system installed. Also, make sure the OSA and Exhaust are set
up on the Zone inputs so that the air handler OSA intake is not
overridden by the inputs in the the zones. On each Zone under the
system under Outside Air & Exhaust enter as follows: Under Outside Air
Flow/Person - Leave this blank. Under Outside Air Flow - Leave this
blank. Under Outside Air Changes - Leave this blank. Under Outside
Air/Flow/Area (CFM/FT2) - Leave this blank.
Then when you do the Revised ECM model with the CO2 demand control then
I would suggest that you set the revised model up something like as
noted below on the 3-23-10 e-mail. This set up will vary the amount of
OSA that is brought in based on the occupancy schedule (which would be
the same on both models) but not allow the ventilation rate to go below
the code required 0.06 CFM/FT2 during occupied times. The OSA is again
closed by schedule when the building is unoccupied.
David Bastow dbastow at mcclure-engineering.com
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Tue Mar 23 08:50:18 PDT 2010
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________________________________
I have used the DCV ventilation method with OA from the system and it
has worked great, as long as you have inputs in correctly under the zone
outside air & exhaust. If you have inputs under the zone incorrectly
then the OA control on the system will be overridden by the inputs under
the zone.
Inputs in the model would be something like this to get it to work:
-Air side HVAC System under outdoor air - vent & economizer:
-Under Min. outside air (ratio)- set at whatever, such as 0.10
for 10% OSA (if using an economizer the minimum must be set at least to
0.001, or the economizer feature will not work in the model).
-Under Min. OA Method - I always use DCV Return Sensor.
-On each Zone under the system under Outside Air & Exhaust:
-Under Outside Air Flow/Person - Input CFM required by code or
usually 15 to 20 CFM per person.
-Under Outside Air Flow - Leave this blank.
-Under Outside Air Changes - Leave this blank.
-Under Outside Air/Flow/Area (CFM/FT2) - Normally I input 0.06
here, which is typically the amount required by the code.
As long as you have your hourly occupancy schedule set up correctly with
the % of the number of people that are in each zone then these inputs
have always worked for me. The Outside Air entering the system will
vary down to as low as 0.06 CFM/FT2 of the area of the applicable zones
depending on how many people your occupancy schedule shows you have in
each of the applicable zones that you have under the HVAC air system.
The Outside air reduction will, of course, also always be limited by the
amount of exhaust CFM that you have input under the zone. Be careful
with what you enter under the zone regarding the CFM of the ventilation
and the exhaust, as the program will always override what you enter
under the system by what you have entered under the zone.
David A. Bastow
McClure Engineering, Inc.
________________________________
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Demba
Ndiaye
Sent: Tuesday, July 27, 2010 1:44 PM
To: Paul Riemer; ron lamarre; 'Carol Gardner'; equest-users
Subject: Re: [Equest-users] Demand Controlled Ventilation and EA Credit
1
I also do not think that modifying the occupancy schedule is a proper
way to account for DCV savings. Doing that, one modifies the loads due
to people.
And the Baseline and Proposed should always have the same occupancy
schedules.
________________
Demba NDIAYE
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Paul
Riemer
Sent: Tuesday, July 27, 2010 2:51 PM
To: ron lamarre; 'Carol Gardner'; equest-users
Subject: Re: [Equest-users] Demand Controlled Ventilation and EA Credit
1
Ron and Carol,
Would you please clarify by referencing EQUEST/DOE-2.2 commands? Are you
modeling DCV by changing the space occupancy schedule (SPACE:
PEOPLE-SCHEDULE)? What are your outside air inputs? Is this the dummy
space in a DOAS system? Are you making other creative changes like
putting all of your occupant heat gain in as a process load? I am
gasping to understand the validity of changing the people schedule.
I have always valid DCV modeling is best done in eQUEST/DOE-2.2 by
changing the system minimum outside air schedule (SYSTEM: MIN-AIR-SCH).
Even just changing the system minimum outside air control method
(SYSTEM: MIN-OA-METHOD) seems iffy because I think the approach that
ignores the floor area component of Std 62.1.
Thanks,
Paul Riemer
Dunham
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bishop,
Bill
Sent: Tuesday, July 27, 2010 1:32 PM
To: James Hansen; ron lamarre; equest-users
Subject: Re: [Equest-users] Demand Controlled Ventilation and EA Credit
1
Ron,
I'm with James on this one. I can see changing lighting or equipment
schedules to capture ECMs but changing occupancy schedules makes no
sense unless you're modeling telecommuting or 4-day work week. You can
capture DCV savings in eQUEST by selecting DCV as the Minimum OA Control
Method for the system and having an occupancy schedule with a varying
percentage (not 100%) during occupied hours. Using the same occupancy
schedule, the model with DCV will heat/cool less OA air and show
savings.
Regards,
Bill
William Bishop, PE, BEMP, LEED(r) AP | Pathfinder Engineers & Architects
LLP
Mechanical Engineer
134 South Fitzhugh Street
Rochester, NY 14608
T: (585) 325-6004 Ext. 114
F: (585) 325-6005
wbishop at pathfinder-ea.com
www.pathfinder-ea.com
P Sustainability - less is more.
________________________________
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of James
Hansen
Sent: Tuesday, July 27, 2010 2:23 PM
To: ron lamarre; equest-users
Subject: Re: [Equest-users] Demand Controlled Ventilation and EA Credit
1
"For the record, the occupancy schedule refers to the people present
within the space. For instance, a space within the baseline (not
required by ASHRAE to have DCV) would have the max number of occupants
for the entire occupied-mode schedule; however, the proposed would have
the max number of people for only as many hours as submitted in the
project narrative for FTE usage of the space, and a minimum number of
people (or no one) for the remaining occupied-mode time. Thus we create
an occupancy (people) schedule for the space. During the unoccupied
mode the fans would cycle as required with no people, no lighting
(automatic shut off), acting on the heating & cooling loads. We would
not install DCV if the occupant loads didn't change during the occupied
mode."
Ron, please educate me if I'm reading your email wrong, but are you
saying that your occupancy schedule in the proposed design does not
match the baseline design? This is strictly prohibited in App G I
thought... You can change schedules to take advantage of non-standard
ECMs like DCV, and automatic lighting reductions for the use of
occupancy sensors (in rooms NOT already required to have them by code).
But having a conference room 100% occupied from 7am-6pm in the baseline
model and only 100% occupied from 9am-noon in the proposed model is not
a valid way to demonstrate savings from DCV, since there will be energy
savings related to the people latent/sensible production that has
nothing to do with DCV. Don't you have to create a minimum outside air
schedule to demonstrate DCV savings? If you have received credit for
simply reducing the Occupancy Schedule in the proposed model, that is
very interesting...
Thanks!
GHT Limited
James Hansen, PE, LEED AP
Senior Associate
1010 N. Glebe Rd, Suite 200
Arlington, VA 22201-4749
703-338-5754 (Cell)
703-243-1200 (Office)
703-276-1376 (Fax)
www.ghtltd.com <http://www.ghtltd.com/>
From: ron lamarre [mailto:lamarre_arch at yahoo.com]
Sent: Tuesday, July 27, 2010 2:08 PM
To: James Hansen; equest-users
Subject: Re: [Equest-users] Demand Controlled Ventilation and EA Credit
1
Hi James:
For the record, the occupancy schedule refers to the people present
within the space. For instance, a space within the baseline (not
required by ASHRAE to have DCV) would have the max number of occupants
for the entire occupied-mode schedule; however, the proposed would have
the max number of people for only as many hours as submitted in the
project narrative for FTE usage of the space, and a minimum number of
people (or no one) for the remaining occupied-mode time. Thus we create
an occupancy (people) schedule for the space. During the unoccupied
mode the fans would cycle as required with no people, no lighting
(automatic shut off), acting on the heating & cooling loads. We would
not install DCV if the occupant loads didn't change during the occupied
mode.
We also use general lighting schedules that take advantage of installed
occupancy sensors, and process load schedules that take advantage of
Energy Star computers and monitiors.
The HVAC engineer decides the minimum design rate for each space to work
(heating & cooling) if fully occupied with all the lights, process
loads, and people during the occupied mode. This is normally at or
above the 62.1 and/or other code-required minimums (never below due to
the LEED pre-requisite). Sharing the reduction schedules placed into
eQuest with a template-narrative to support the reductions (based on
ASHRAE 90.1, Energy Star, etc... %-reductions) has been accepted by
LEED.
We utilize an integrated design team method, where the engineers and I
review the models that I construct. We also get peer reviews when we
think it's necessary and/or when LEED throws us a curve. We pay for our
peer reviews. I'm confident that anything we've submitted does not
prove inconsistency within the review of EAc1.
Ron Lamarre, AIA, NCARB
Architect - LEED AP BD+C
Design + Energy Modeling + LEED Administration
________________________________
From: James Hansen <JHANSEN at ghtltd.com>
To: ron lamarre <lamarre_arch at yahoo.com>; Karen Walkerman
<kwalkerman at gmail.com>;
Sent: Tue, July 27, 2010 12:57:21 PM
Subject: RE: [Equest-users] Demand Controlled Ventilation and EA Credit
1
"Each model that I've done for LEED utilizes the same ventilation rates
between the proposed and design; whether it was ASHRAE 62.1 or IMC 2003;
however, the occupancy schedules changed in spaces where DCV was
installed."
Ron, that's an interesting statement in itself - modifying occupancy
schedules has an impact on the mechanical cooling (not just the cooling
associated with reduced ventilation air), which isn't really fair. Was
that approved by GBCI? If so, I guess it's further proof that there is
still a lot of inconsistency in the review of EAc1.
Karen, I think your letter does a good job of requesting an official
"ruling" from the USGBC.
GHT Limited
James Hansen, PE, LEED AP
Senior Associate
1010 N. Glebe Rd, Suite 200
Arlington, VA 22201-4749
703-338-5754 (Cell)
703-243-1200 (Office)
703-276-1376 (Fax)
www.ghtltd.com <http://www.ghtltd.com/>
________________________________
From: Karen Walkerman <kwalkerman at gmail.com>
To: equest-users <equest-users at lists.onebuilding.org>
Sent: Tue, July 27, 2010 12:10:27 PM
Subject: [Equest-users] Demand Controlled Ventilation and EA Credit 1
All,
below is a draft letter to the EA Credit 1 TAG chair. I welcome any
edits, or critiques, and if anyone would like to be a co-signer of the
letter, please let me know.
Thanks,
--
Karen
It has come to our attention from a posting on the eQuest list-serve
that a fellow energy-modeling professional has been asked to model
proposed design and baseline design ventilation rates differently where
the proposed design model utilizes demand controlled ventilation. We
have searched the ASHRAE 90.1 documentation as well as the LEED
reference documentation and consistently find the requirement that
baseline ventilation rates be modeled the same as the proposed design,
and that credit can be taken for demand controlled ventilation.
We understand that large energy savings can be gained from demand
controlled ventilation and that in certain cases, 'gaming' of the system
could result in abnormally high ventilation rates for the baseline
design, while the DCV system keeps ventilation rates low in the proposed
design, however, our main concern is that energy modelers are being made
aware of changes to guidelines during the design review process. At
this stage, the energy modeler has already completed a significant
amount of work in preparing the proposed and baseline design energy
models, and all associated documentation. Changing the baseline design
ventilation rates requires re-modeling of the building and increases the
likelihood that the project will have to challenge a 'rejected' result
if the LEED reviewer is not satisfied with the energy modeler's response
and modeling changes.
We feel that it may be time to develop modeling guidelines for demand
controlled ventilation, and that these guidelines should be developed,
released, and required in a similar fashion to the district energy
guidelines published by LEED for NC 2.2 Furthermore, we feel that any
changes made to EA Credit 1 energy modeling guidelines should be made
with adequate notice to the energy modeling community.
Thank you for your consideration on this issue,
--
Karen Walkerman
Second Law
________________________________
The information contained in this communication is confidential, may be
privileged, and is intended only for the use of the addressee. It is
the property of GHT Limited. Unauthorized use, disclosure or copying of
this communication or any part thereof is strictly prohibited and may be
unlawful. If you have received this communication in error, please
notify me immediately by return e-mail or by e-mail to ght at ghtltd.com
<mailto:ght at ghtltd.com> , and destroy this communication and all copies
thereof, including all attachments. Thank you.
________________________________
The information contained in this communication is confidential, may be
privileged, and is intended only for the use of the addressee. It is
the property of GHT Limited. Unauthorized use, disclosure or copying of
this communication or any part thereof is strictly prohibited and may be
unlawful. If you have received this communication in error, please
notify me immediately by return e-mail or by e-mail to ght at ghtltd.com
<mailto:ght at ghtltd.com> , and destroy this communication and all copies
thereof, including all attachments. Thank you.
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