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

[Carol Gardner]

Karen,

Great job on the letter. I got out my special editor's pen, shook the dust
off, and have some suggestions below:

It has come to our attention from a posting on the eQuest listserv 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 (DCV).  We have researched 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. We think that
the requirement for the ventilation rate not to change between the baseline
and proposed buildings already limits this possibility, however, and our
main concern is that energy modelers be made aware that changes to the
LEED guidelines
may be made 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 think 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 think 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,

I would be happy to be a cosigner but since I am not a LEED AP or a BEMP or
anything except a PE you may be able to find someone more impressive.

With respect to James' comment below, I have also modified the occupancy
schedule to model DCV. I simply renamed it "DCV Occ Sch", or something like
that and applied it only to the space that was using DCV. Easy enough to do
and no impact on the mechanical cooling at all. This reminds me of the
discussion the other week about using a schedule to reflect lighting W/sf
reductions vs, just reducing the W/sf itself. When I have some spare time to
mull the costs/benefits of using schedules vs. direct reductions I will. If
others have some thoughts I encourage them to share them.

The last thing I want to say is that this listserv is great! I guess I'm a
real nerd cause I love discussions like this one here about DCV where people
have obviously given the matter a lot of thought and feel free to express
their opinion, whether popular or not. We are really a lucky group of
professionals to have such a resource.

Carol


On Tue, Jul 27, 2010 at 9:57 AM, James Hansen <JHANSEN at ghtltd.com> wrote:

>  “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)
>
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>
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> 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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-- 
Carol Gardner PE
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