[Equest-users] GBCI comments on DCV (Carol Gardner)
Cam Fitzgerald
cam at energyopportunities.com
Tue Jul 27 08:57:26 PDT 2010
Paul, et al:
Without going into great detail, I take exception to the statement that
"62.1 and its user's manual throw up their hands on DCV in multi-zone
systems." It seems to me that the 62.1-2004 User's Manual is quite
specific about how the minimum ventilation rates should be determined
when a multi-zone systems serves spaces with and without DCV starting on
page A-5. You may want to review this guidance.
Cam Fitzgerald
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 11:42 AM
To: 'Karen Walkerman'; James Hansen
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] GBCI comments on DCV (Carol Gardner)
I nodded somewhat along with Karen's email but we probably need to
sharpen the saber in addition to rattling it.
Demand Controlled Ventilation (DCV) is a control approach. Std 62.1 is
a largely about quantitative ventilation thresholds. Std 90.1 requires
DCV in some instances but control approach, It does not reference
specific maximum or minimum, design or operating ventilation thresholds.
So a 90.1 compliant design can use DCV to modulate between thresholds
set by professional judgment, local code, exhaust/pressurization
concerns, or even an owner requirement such as 30% above Std 62.1.
It really is a complex intersection of LEED, Std 62.1 and Std 90.1 and
prone to collusions. Even Standard 62.1 and its users manual essentially
throw up their hands on DCV in multi-zone systems.
Consider a project that is required to implement DCV in some space, and
it does so but not to the GBCI's interpretation of Std 62.1 values. Do
the differences count for and/or against its EAp2 compliance and/or its
EAc1 points? What if the project is IEQc2 Increased Ventilation? What
if the project is also implementing DCV in spaces not required to have
it? Does it matter if it is based on sensing CO2, sensing occupancy, or
time of day? What if they proposed and baseline mechanical systems are
multi-zone, single zone, or one of each? ...
This is so complex, I can see why they are reacting project by project.
I would take the review Thomas shared as one point in the discussion,
not universal guidance for all projects. They cannot possibly be smart
enough to write guidance for all cases without sacrificing something
currently held sacred by someone.
With every model and especially every exceptional calculation the
modeler should build reasonable models and be prepared to justify them
as reasonable. With DCV the justification probably needs to be in the
initial submittal.
Paul Riemer
Dunham
From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Karen
Walkerman
Sent: Tuesday, July 27, 2010 8:33 AM
To: James Hansen
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] GBCI comments on DCV (Carol Gardner)
You are missing the fact that the rules are being changed at the REVIEW
stage. This requires the energy modeler to do a-lot of extra work to
change the baseline model during the review stage. It also means that
after changing the model, if the reviewer has any additional comments or
questions, the energy modeler will have to go through an additional
review, and pay an additional fee to have the USGBC look at their
documentation again.
Also, the fact that this rule seems to be implemented for some projects,
and not for others means that buildings are not being rated fairly
against each other.
The debate about whether this makes sense or not should be kept separate
from this discussion. My main concern is that rules are being changed
without letting the players know. Any time they make changes, it needs
to be documented publicly, preferably with changes only applying to
projects registered after the date of publication.
We can debate separately whether this rule change makes sense. Yes, I
understand that some "gaming" of the system could happen, in theorgy,
but in many cases, adding HUGE amounts of outdoor ventilation air as you
suggest is far too costly to implement.
Thanks,
--
Karen Walkerman
On Tue, Jul 27, 2010 at 9:13 AM, James Hansen <JHANSEN at ghtltd.com>
wrote:
I'm not sure I really understand what the fuss is about. If you're
designing and modeling a building that does NOT have DCV, then it seems
entirely fair (and accurate) to model the same ventilation rates in both
the baseline and the proposed. If, however, you are implementing a DCV
strategy, then regardless of what you set your "maximum" OA rate at for
the proposed model, in reality, the DCV system is going to keep OA flow
rates near or below the ASHRAE 62.1 requirements (in real life
operation).
If the TAG committee didn't require you to model the baseline building
at ASHRAE 62.1 flow rates when DCV is being implemented, then
theoretically you could input an astronomically high OA flow rate for
both models, knowing that your proposed model would NEVER run at such a
condition and would have an unfair advantage.
This seems like an entirely acceptable and fair ruling. What am I
missing?
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: equest-users-bounces at lists.onebuilding.org [mailto:
equest-users-bounces at lists.onebuilding.org] On Behalf Of Karen Walkerman
Sent: Tuesday, July 27, 2010 9:05 AM
To: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] GBCI comments on DCV (Carol Gardner)
Is anyone on this list-serve on the EA Credit 1 committee, or know
someone who is? If the the GBCI or USGBC has changed the modeling
requirements and is only letting modelers know during the documentation
review stage, I find this very disturbing for a number of reasons. It
would be great if we can get some straight answers on this from someone
at one of these organizations who actually knows what is going on.
I am happy to draft an email outlining concerns, but I don't know who to
send it to. If anyone does, or would like to help me with this, please
feel free to contact me directly.
Thanks,
--
Karen Walkerman
On Tue, Jul 27, 2010 at 8:28 AM, Peter Worley <peter.worley at arup.com>
wrote:
Sorry for what may seem like a dumb question...
Why, if you're designing to ASHRAE 62.1, would you increase the outside
air quantity beyond the minimums (unless required for lab exhaust, etc)?
I have a project where the local code (referencing IMC 2003) requires a
higher level of minimum ventilation than ASHRAE 62.1. I've therefore
designed to this amount and modeled it in both my proposed and baseline
cases. I can't imagine that this will be problematic. Do you disagree?
Thanks,
Pete
Peter Worley
Mechanical Engineer
155 Avenue of the Americas New York NY 10013 USA
t +1 212 229 2669 d +1 212 897 1339
f +1 212 229 1056
www.arup.com
From: Tom Serra [mailto:tserra at emoenergy.com]
Sent: Monday, July 26, 2010 12:14 PM
To: Karen Walkerman
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] GBCI comments on DCV (Carol Gardner)
No documentation exists supporting the new method. GBCI is pulling the
"rating authority" card and implementing their own requirements. I
tried to argue my case that they are going against the procedure in
ASHRAE, but they did not change their requirement. I have expressed my
opinion that a document should be posted on the website that shows this
new requirement but I have yet to see anything new. Otherwise you may
be expecting savings from DCV that will be rejected and then the MEP or
modeler will look foolish. They should have implemented a cut-off date
for projects already in the system similar to the "District Thermal"
change they made in May 2008.
In reality the DCV will still result in energy savings but the paper
design savings will be lost. I believe GBCI and USGBC are trying to
prevent "gaming" of the system. A designer could grossly oversize the
ventilation system and then gain tremendous savings by implementing DCV.
This new requirement forces the designer to pursue other ventilation
strategies if they want to claim savings for DCV. Unfortunately the
only way we are learning of this requirement is through clarification
questions. This lack of communication is what really upsets me.
The only solution that I see is that all spaces with demand control
ventilation should be designed to ASHRAE 62.1 minimums. Also, teams
should not pursue the 30% increase ventilation credit.
Thomas Serra
Project Manager
EMO Energy Solutions, LLC
3141 Fairview Park Drive, Suite 450
Falls Church, VA 22042
voice 703-205-0445 ex-113
fax 703-205-0449
On Mon, Jul 26, 2010 at 11:22 AM, Karen Walkerman <kwalkerman at gmail.com>
wrote:
Can anyone find documentation requiring the baseline to use ASHRAE 62.1
ventilation rates? The table in EA Credit 1 under HVAC System Selection
for the baseline design states:
"Outdoor ventilation rates should be identical to the proposed case"
There are no exceptions listed anywhere in the LEED documentation (I am
currently looking at LEED 2009, but have reviewed this in the past under
LEED 2.2).
We have had DCV be approved in the past with no questions.
--
Karen
On Mon, Jul 26, 2010 at 11:08 AM, Tom Serra <tserra at emoenergy.com>
wrote:
I've had many comments. They have changed their perspective as
the rating authority and are requiring outside air treatment procedures
that are outside of ASHRAE 90.1 section G procedures. Typically design
outside air volume is the same between the baseline and proposed, but if
you are using DCV they now require you to model the baseline with the
minimum ASHRAE 62.1 volume. So, if you have greater OA volume in your
proposed model, you may be penalized depending on your DCV method and
diversity schedule for occupants in the area with DCV control.
Here is an example clarification question:
1. CLARIFY: Demand control ventilation was modeled for
credit for RTU1 and RTU2 in the Proposed case as indicated in Table 1.4
of the Template; however, the outdoor air volume for RTU1 and RTU2 in
the Baseline model was not modeled at the ASHRAE 62.1-2004 minimum rates
(1,066 cfm for each RTU) as determined in EQp1: Minimum IAQ Performance.
Appendix G allows schedule changes for demand control ventilation as
approved by the rating authority (Table G3.1.4(Baseline)). As the rating
authority, GBCI requires that the outside air ventilation rates for the
Baseline Case be modeled using minimum ASHRAE 62.1-2004 rates wherever
credit is taken for demand control ventilation in the Proposed Case. The
Proposed case minimum rates at design conditions must be modeled as
designed.
TECHNICAL ADVICE: Revise the Baseline model so the minimum
outdoor air volume is modeled at 1,066 cfm for RTU1 and RTU2 in the
Baseline model. In addition, provide revised SV-A reports for RTU1 and
RTU2 reflecting the changes. Further, 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 must
be modeled identically in the Baseline and Proposed Case).
Thomas Serra
Project Manager
EMO Energy Solutions, LLC
3141 Fairview Park Drive, Suite 450
Falls Church, VA 22042
voice 703-205-0445 ex-113
fax 703-205-0449
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