[Equest-users] GBCI comments on DCV (Carol Gardner)

[Jeremy Poling]

Tough situation - let me take you where I might go with this one
(hopefully it helps!):

 

ASHRAE 90.1-2004 and ASHRAE 90.1-2007 state the same thing in Appendix G
regarding energy savings from DCV with the exception of the referenced
mandatory DCV requirement (2004 is Section 6.4.3.8 while 2007 is Section
6.4.3.9):

 

"G3.1.2.5 Ventilation.  Minimum outdoor air ventilation rates shall be
the same for the proposed and baseline building designs.

 

Exception to G3.1.2.5: When modeling demand-control ventilation in the
proposed design when its use is not required by 6.4.3.8."

 

The main difference is in the referenced section.  In 2004 the mandatory
requirement was DCV for systems with supply OA exceeding 3000 CFM and
serving areas with occupant densities over 100 people per 1000 SF.  In
2007, this was made more stringent: spaces over 500SF with occupant
densities over 40 people per 1000 SF served by systems having an
air-side economizer, automatic modulating control of the OA damper, or a
design OA exceeding 3000 CFM.  Remember - these are the criteria that
disallow the exception to G3.1.2.5.

 

This is consistent with part of what your review comment states - ASHRAE
90.1 does not require you to model the DCV rates the same in the
baseline and proposed case and the rating authority (ASHRAE's term, not
the GBCI's or USGBC's term) can take a position that the exception is or
is not allowed.

 

That said, I would specifically take issue with the GBCI stating that
they are the "rating authority".  They are only allowed to determine if
the project has complied with the LEED standard as the USGBC has
published it.  If the reference guide and rating system in effect at the
time your project was registered do not state what the reviewers did,
file a customer service request with both the USGBC and GBCI outside of
the review process to request that they address this.  I have been told
the backlog on this type of issue is 4-8 weeks, but you could be lucky
(as I have been on occasion) and get a response quickly.  

 

The GBCI does not write the LEED rating system - they just certify
projects against the standard.  I would also request specific
documentation of where that requirement is referenced in ASHRAE 90.1,
ASHRAE 62.1 and/or the LEED rating system and appropriate reference
guide.

 

This is one of those areas we do bring up with clients - more outdoor
air, regardless of why you have it in the building, will carry an energy
premium.  The amount of OA for a design needs to be carefully planned.
The credit for exceeding ASHRAE 62.1 by 30% is still only worth 1 point
and the cost/benefit analysis of the extra outdoor air may not make
sense for a given project.  We've had a number of clients skip that one,
especially those who cannot use productivity as part of their financial
justification (yup - they are out there!).

 

The prerequisites trump credits usually in the LEED review, so at the
very least your reviewer is assuming that since the prerequisite
requires you to provide ASHRAE 62.1 minimum OA then any DCV strategy NOT
required by ASHRAE 90.1 6.4.3.8/9 would be optional and part of the
design model but not the baseline.

 

Good luck!

 

JEREMY R. POLING, PE, LEED AP
Associate Vice President,

Senior Sustainability Analyst
Strategic Services
Site Solutions | Operations | Sustainability

EPSTEIN

Epstein is a firm believer in sustainability. We ask that you please
consider the environment before printing this e-mail.

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Tom
Serra
Sent: Monday, July 26, 2010 11:14 AM
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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