[Bldg-sim] How have you approached... (UNCLASSIFIED)
Nick Caton
ncaton at smithboucher.com
Wed Jul 20 08:45:16 PDT 2011
Thanks so much for the suggestions!
I myself have tread the "extensive, realistic fractional/thermostat
scheduling" path before under similar circumstances. Upon facing a VERY
large project, where the amount of explicit scheduling required for that
approach is compounded by the sheer quantity and variety of occupied
spaces benefiting from this relay setup, I am challenged with
brainstorming any acceptable (by LEED reviewer) means of approximating
the same behavior/savings by simplifying the problem...
Here are some alternative ideas we've come up with so far - I would
very much appreciate others' thoughts on these, or any further related
LEED/USGBC experiences to share as well:
1. 90.1 already prescribes how we quantify the savings of
occupancy sensors for installed lighting (10 or 15% flat deduction on
the LPD). Rather than define & justify the quantity and timing of
unoccupied hours between varying space types (murky waters at best), one
could instead reduce the loads incident on the affected systems by the
same percentage. This might be accomplished by applying this 10/15%
deduction to the affected spaces' fractional load schedules (occupancy,
equipment & lighting). One would need to tread carefully to avoid
"double-dipping" on any spaces already claiming a LPD deduction for
occupancy sensors. Baseline model's schedules would remain unaffected
and would be documented alongside the modified ones to illustrate the
difference.
2. (Simpler to model, but requiring slightly more documentation):
Let's say a hospital has an annual average of 85% occupancy for all its
patient rooms. Treating every other room normally, select a
representative sampling (considering envelope loads) of 15% of the
patient rooms. Model those selected rooms as "empty" (set people,
lights and equipment loads = 0) but still conditioned to maintain the
thermostat setpoint (against loads incident from the envelope &
neighboring spaces). Apply the 0% minimum turndown behavior to those
"empty" rooms only. Baseline model would receive identical treatments,
excepting the 0% turndown behavior. Documentation would include
illustrating which zones were sampled against the others, and
justification for the net annual "occupancy rate" used for each space
type.
I have mixed feelings - obviously any simplification of the problem has
the potential to under/overstate the savings that might be found with a
more exhaustive scheduling approach, but may result in as good or even a
better estimation provided with solid documentation and execution. Does
anyone think the above approaches could work well, or have any
suggestions to refine the strategies?
Thanks again!
~Nick
NICK CATON, P.E.
SENIOR ENGINEER
Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com
-----Original Message-----
From: James Hansen [mailto:JHANSEN at ghtltd.com]
Sent: Wednesday, July 20, 2011 8:40 AM
To: Eurek, John S NWO; Nick Caton; bldg-sim at lists.onebuilding.org
Subject: RE: [Bldg-sim] How have you approached... (UNCLASSIFIED)
I agree with John, I've done this on a model before and its painful.
Assuming there are 10 hours in a work day, I set up 10 different
occupancy and lighting schedules, each schedule being essentially
identical except for a different hour of zero occupancy / lighting. I
then applied these 10 schedules to the different office zones on a floor
so that specific areas were vacant from 8am-9am, some vacant from
9am-10am, etc. And then for my system, I assumed relatively consistent
10% non-occupied conditions and reduced the OA at the system level
accordingly. If your non-occupied conditions are more drastic (30%),
obviously you can set up your schedules differently.
However, if your primary air is also cooling (and not some sort of DOAS
chilled water VAV box), then you are going to also have to specify 10
separate thermostat schedules (really 20 with heating and cooling) so
that the rooms do not have unmet load hours. I'm assuming you go into
setback mode when the offices are unoccupied.
However, this was under v2.0, so that was a long time ago and reviewers
were not as critical in their reviews.
GHT Limited
James Hansen, P.E., LEED AP
Senior Associate
1010 N. Glebe Road, Suite 200
Arlington, VA 22201-4749
703-243-1200 (office)
703-338-5754 (cell)
703-276-1376 (fax)
www.ghtltd.com
-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Eurek, John
S NWO
Sent: Wednesday, July 20, 2011 9:31 AM
To: Nick Caton; bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] How have you approached... (UNCLASSIFIED)
Classification: UNCLASSIFIED
Caveats: NONE
Nick,
I would do it with schedules. This would be the long method.
I have the same controls and have not got around to model it. I would
also
make many schedules. A different schedule for occupancy, lights,
equipment,
ect. Also if this applies to a lot of rooms, you'd likely make multiple
schedules, one assuming that the room is empty from 9~10 another room
empty
from 2~3. (The inverse for meeting rooms, if you have multiple meeting
rooms, not all meetings will happen at the same time.)
"Is Freedom a small price to pay to stop Global Warming?"
John Eurek PE, LEED AP
Mechanical Engineer,
-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nick Caton
Sent: Tuesday, July 19, 2011 3:59 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] How have you approached...
I have a precedent question for everyone... this is not a "how to"
procedural
question for any particular software, but to simply feel out what has
worked
for others in the past:
Here's a quick description of the situation at-hand: a VAV terminal
unit
with a "normal" minimum damper position (say, 30%) is tied by relay to
the
space occupancy sensor, which also controls the lights. Upon sensing
space
vacancy, the minimum airflow damper position is reset to 0% (airflow is
permitted to stop, provided thermostat temperature set point is
satisfied).
Upon sensing occupancy, the preset minimum damper position is restored.
For LEED/USGBC-reviewed energy models, can anyone relate success in
modeling
this or a similar energy-saving behavior in the proposed model, distinct
from
the baseline? If so, what approach did you use to model this behavior
and/or
quantify the energy savings?
I was discussing the possibilities with some colleagues and have a few
ideas
for approaches that might all be justifiable, ranging from simple (and
quick)
to complex (and time-consuming).
There are likely multiple "right" answers here, but I am hoping to
identify
some precedent to understand what we can anticipate the LEED
reviewership
will accept.
Thanks in advance!
~Nick
cid:489575314 at 22072009-0ABB
NICK CATON, P.E.
SENIOR ENGINEER
Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com
Classification: UNCLASSIFIED
Caveats: NONE
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