[Equest-users] Demand Control Ventilation - LEED Model

[Sheila]

Good morning gentlemen,

 

May I suggest that since eQuest has implemented DCV as an OA control
method, you should no longer have to rely on schedule changes to
document savings from DCV.  Set the OA control method to "DCV Return
Sensor" and the Min OA sizing method to "Set by Critical Zone".   As
stated in the DOE2 help screen for min OA sizing method, "Set by
Critical Zone" uses the same method that ASHRAE 62 uses to determine the
minimum OA for multi-zone systems.

 

Even though Appendix G allows schedule changes to model DCV, be aware
that both the initial schedule and the revised schedule must be
presented along with a complete narrative justification for the changes
in the schedule.  And, it should NOT be the occupancy schedule which
changes, but the minimum OA schedule which changes in response to the
hourly variation which exists in the occupancy schedule.

 

Regards,

 

Sheila Sagerer

Energy Engineer, EIT, LEED AP

Energy Opportunities, Inc, a 7group company

Phone: 717-880-9069

www.sevengroup.com

 

From: equest-users-bounces at lists.onebuilding.org
[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Scott
Janssen
Sent: Wednesday, August 11, 2010 10:30 AM
To: Bishop, Bill
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Demand Control Ventilation - LEED Model

 

The baseline model is dependent on the hourly occupancy schedule
fraction as well, even though it's using "Fraction of Design Flow" as
the OA control method (I just tried adjusting the baseline model and it
is significantly affected by changing the occ schedule fractions);  The
baseline system is a packaged VAV, that may be why.

 

Table G3.1 of Appendix G states that the schedules may be allowed to
differ between the proposed and baseline case to model nonstandard
efficiency measures including DCV, provided the revised schedules have
the approval of the rating authority.  I'm not sure what the rating
authority will allow, but it seems to me that in this case using a
revised schedule in the proposed case would be appropriate.

 

Scott Janssen EMIT, LEED(r) AP 

Energy Analyst

 

EYP Energy 

NanoFab East, Suite 1400 / 257 Fuller Road / Albany, NY 12203

T (518) 438 - 1497 / C (518) 421 - 1267 / eypae.com
<http://www.eypae.com> 

 

/ 2009 Best Firm to Work For

 

From: Bishop, Bill [mailto:wbishop at pathfinder-ea.com] 
Sent: Wednesday, August 11, 2010 10:17 AM
To: Scott Janssen
Cc: equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Demand Control Ventilation - LEED Model

 

Scott,

 

The baseline model ventilation will be constant during occupied hours
and equal to peak occupancy x cfm/person when using "Fraction of Design
Flow" as the OA control method. The proposed model hourly ventilation
rate will vary and will be equal to peak occupancy x cfm/person x hourly
occupancy schedule fraction.

 

Bill

 

________________________________

From: Scott Janssen [mailto:sjanssen at eypae.com] 
Sent: Wednesday, August 11, 2010 10:03 AM
To: Bishop, Bill
Cc: equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Demand Control Ventilation - LEED Model

 

Bill,

 

Thanks for the response.  I'm a bit confused as to how that would reduce
ventilation in the proposed case though if everything is the same
between the two models (same fractions in occ schedules, same space peak
occ, same zone level OA cfm/person).  Am I missing something?

 

Thanks, 

 

Scott Janssen EMIT, LEED(r) AP 

Energy Analyst

 

EYP Energy 

NanoFab East, Suite 1400 / 257 Fuller Road / Albany, NY 12203

T (518) 438 - 1497 / C (518) 421 - 1267 / eypae.com
<http://www.eypae.com> 

 

/ 2009 Best Firm to Work For

 

From: Bishop, Bill [mailto:wbishop at pathfinder-ea.com] 
Sent: Wednesday, August 11, 2010 9:15 AM
To: Scott Janssen
Cc: equest-users at lists.onebuilding.org
Subject: RE: [Equest-users] Demand Control Ventilation - LEED Model

 

Scott,

 

Check the equest-users archives since this has been discussed many
times. You are on the right track.

 

You have to use the same occupancy schedule(s) for your proposed and
baseline models. Enter the peak occupancy for your space and then
create/adjust your occupancy schedule so that it fluctuates somewhere
between 0 and 100% during occupied hours, according to how the space is
actually used. If you set your zone-level OA with the same cfm/person
value in both the proposed and baseline, the proposed will decrease the
ventilation during occupied hours based on the fraction of occupancy in
the schedule. Make sure you are not "gaming the system" - your peak
occupancy and cfm/person values that you use should be consistent with
the actual mechanical design peak ventilation rate.

 

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 Scott
Janssen
Sent: Wednesday, August 11, 2010 9:00 AM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Demand Control Ventilation - LEED Model

 

My question is in regards to setting up the design case model to reflect
demand control ventilation.  So far, I've set the min OA schedules for
the zones to 0 during unoccupied hours to limit OA and set the HVAC
system min OA method to DCV return, and this has shown some savings.
The occupied hours for some of the spaces are roughly 12 hrs/day, but
the spaces will be occupied roughly 1/3 of the time during those hours.
As this project is going for LEED, is it acceptable to adjust the
occupancy schedules in any way to account for the effectiveness of the
DCV system when these spaces are "unoccupied" during occupied hours, or
does anyone have any suggestions for other changes I can make to the
design case model?  This is really an ideal scenario for DCV as the
occupied schedule for the building is long (at least 12 hrs per day),
but the actual occupancy of the building will be sporadic and I'm
concerned that the model isn't reflecting the full-effectiveness of the
DCV system.

 

Thanks in advance, 

 

Scott Janssen EMIT, LEED(r) AP 

Energy Analyst

 

EYP Energy 

NanoFab East, Suite 1400 / 257 Fuller Road / Albany, NY 12203

T (518) 438 - 1497 / C (518) 421 - 1267 / eypae.com
<http://www.eypae.com> 

 

/ 2009 Best Firm to Work For

 

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