[Equest-users] Demand Controlled Ventilation and EA Credit 1

[James Hansen]

"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

 

 

 


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