[bldg-sim] Occupancy Sensors

[Molly Curtz]

Hi Bill-
I do not have direct experince obtaining LEED credit for Occupancy Sensors,
but I too am currently looking into this issue for a LEED project.

As you note, It's my understanding that USGBC has not yet formally adopted
either 90.1-2001, or addendum e to 90.1-2001. (Rumor has it that they will
update directly to 90.1-2004 when they do update.)

I interpret the table G3.8 in addendum e to 90.1-2001 to show the suggested
adjustments to proposed L.P.D levels. I agree that the language of:
'automatic lighting controls in *addition* to those required  for minimum
code compliance.' is very confusing. However, I think that adjustments are
suggested according to the table listings based on use type either " Non
24-hour use and Less than or equal to 5,000 sq.ft." OR "All Other Spaces".
My reading is that even though automatic shutoff controls are listed as a
mandatory measure for "All other" spaces in 90.1 1999 section 9.2, that the
listed L.P.D. adjustments for installation of either programmable timing
control, Occupancy Sensor, or Both are allowed. (Note that the listed
adjustment under "All Other", " Programmable timing control" is zero
adjustment.)

Still , keep in mind that addendum e is not offically adopted by USGBC yet.

For now, I'm working from 90.1-1999 and the published USGBC CIRs. There is a
Credit Interpretation Request that you have access to on the USGBC web site
if your organization is a USGBC member. I've copied the text below in case
some list members do not have access to the CIRs.(see below.) The ruling on
Measure 1 is the pertinent one, which states adjustment of L.P.D. may be an
acceptable means of approximating Occupancy sensors without modifying the
schedules between proposed and baseline.

I have anecdotally heard that other projects used an adjustment of 20% in
the proposed L.P.D. for an office use and received credit. I'm planning on
trying this adjustment for the model I'm working on (since it's 5% more than
the addendum e listing).

Best wishes,
Molly Curtz
Ecotope Inc.                   p: (206) 322-3753
4056 9th Avenue NE      f: (206) 325-7270
Seattle, WA  98105        www.ecotope.com


      12/2/2003 -  Credit Interpretation Request
      Four energy-efficiency measures, which are not covered under ASHRAE
90.1-1999 or the LEED Energy Modeling Protocol, are outlined below for a
106,000 square foot chemistry research laboratory building with numerous lab
fume hoods. These four measures generate significant energy cost savings.

      Based on the following USGBC Credit Rulings posted on 06/07/2001,
06/27/2001 and 01/20/2002:
      "To document savings for [energy reducing strategies not covered under
ASHRAE 90.1-1999 or the LEED Energy Modeling Protocol], follow the ECB
Exceptional Calculation Method. See Section 11.5 of the ASHRAE 90.1 User''s
Manual. Under the ECM, schedule variations may be used as a basis of
engineering calculations for discrete measures that are precluded by the
reference standard or the LEED EMP."

      We assume each energy-efficiency measure listed below should be
modeled discreetly and "exceptional" savings must be subtracted from the
Design Energy Cost in the same fashion as renewable energy.

      Based on the USGBC''s LEED Credit Ruling posted on 11/09/2001:
      "It is acceptable to use [the same simulation tool that is used for
the base simulation] to triangulate on projected savings for discrete
measures that can ONLY be approximated through schedule manipulations."

      We assume that these Exceptional Calculation Methods (ECM''s) are to
be performed using the same simulation tool that is used for the base
simulation.

      For the first three energy-efficiency measures listed below, a
corresponding reduction in energy use can only be approximated by altering
the Base Building schedules (based on sound engineering judgement).
Therefore, we hereby request preliminary approval for the first three energy
saving measures listed. Hourly schedules for lighting power density and
fumehood exhaust in both the Design Building and Base Building are available
for each case for review.

      1. Lighting Occupancy Sensors
      When motion and/or infrared sensors determine a space to be unoccupied
for a period of at least 15 minutes (adjustable), lighting within the space
is automatically reduced to minimum levels.

      2. Fumehood Zone Presence Sensors
      When locally mounted infrared sensors determine the zone in front of a
particular fumehood to be unoccupied for a period of at least 15 minutes
(adjustable), laboratory exhaust quantities shall be adjusted to reduce sash
velocity from 100 fpm to 70 fpm for that individual fumehood.

      3. Fumehood Occupancy Sensors
      Similar to Lighting Occupancy Sensors, when motion and/or infrared
sensors determine a space to be unoccupied for a period of at least 15
minutes (adjustable), laboratory exhaust quantities shall be adjusted to
reduce the minimum total room air change rate from 12 ACH to 6 ACH.
      Additionally, we request preliminary approval for the following energy
saving measure, to be modeled as noted below:

      4. Laboratory Air Cascading
      A portion of the makeup air required for fumehood exhaust shall be
delivered to offices and support areas and then "cascaded" to labs via a
ducted transfer air system. Ducts shall be sized so that the external
pressure drop realized along the path of the transfer air shall be a maximum
of 0.05" w.g.

      The Exceptional Calculation Method proposed would compare two
analogous air-handling system (one for office/support areas and one for the
laboratories), by breaking the air-handling system into two discreet pieces,
to facilitate comparison of the Base and Design building models.

      2/4/2004 -  Ruling
      ENERGY EFFICIENCY MEASURE 1:
      It appears that altering the schedule to approximate energy savings
from the lighting occupancy sensors (as described) fits within the context
of the 90.1 Exceptional Calculation Method. When calculating the energy
savings associated with these measures for EAc1, it is necessary to justify
both the proposed and budget schedules for occupied hours and provide
detailed space by space usage schedules that are both reasonable and
defensible. The budget and proposed building should have the same lighting
schedules for regularly unoccupied periods. Additionally, it may be possible
to arrive at a reasonable estimate by manipulating the lighting power
density in the proposed and design case.

      ENERGY EFFICIENCY MEASURES 2 AND 3:
      Fumehoods are considered process loads, which are not applicable to EA
Prerequisite 2 and EA Credit 1. The appropriate treatment of laboratory
process loads is the subject of numerous LEED CIRs. Please refer to the EAp2
credit ruling dated 12/15/03 and EAc1.1 credit ruling dated 12/15/03 for a
discussion of the appropriate treatment of ASHRAE 90.1 non-regulated energy
loads in EAc1. To maintain consistency with the referenced standard,
optimization of non-regulated energy loads is recognized by award of an
Innovation in Design (ID) credit rather than award of EAc1 points.
      For ID credit calculations, it appears that altering the schedule to
approximate energy savings from the fumehood zone presence sensors and the
fumehood occupancy sensors (as described) fits within the context of the
90.1 Exceptional Calculation Method. When calculating the energy savings
associated with these measures for ID credit award, it is necessary to
justify both the proposed and budget fumehood schedules for occupied hours
and provide detailed laboratory usage schedules that are both reasonable and
defensible. The budget and proposed building should have the same
ventilation rates for regularly unoccupied periods. If any of the zones are
internally load driven, the potential energy savings from reducing the
ventilation requirements must account for the possibility of higher
ventilation rate requirements imposed by internal loads.

      ENERGY EFFICIENCY MEASURE 4:
      The ECM proposal does not contain sufficient detail from which to make
an informed determination. It is likely that it will be allowed during LEED
certification review if ASHRAE 90.1 Section 11.5 guidance is followed (i.e.,
provide theoretical and empirical information verifying accuracy). Also
consider this alternative approach: the lab could be modeled as a 100%
outside air system for the baseline case but as a recirculating system for
the proposed design. The outside air quantities and relief quantities for
the office space would be modeled as identical. The fan power and schedule
would be identical for the supply and exhaust systems for laboratory and
office areas. To model the cascading system in the proposed design, the
laboratory system recirculates the volume of relief air that would be
cascaded from the office space to the laboratory space. The total amount of
outside air drawn into the building is reduced in the proposed design by the
amount of relief air that is cascaded from the office occupancy to the
laboratory. The outside air ventilation volumes and exhaust volumes are
identical for the two cases (the outside air discrepancy is due to a make-up
air, rather than a ventilation air requirement).

----- Original Message ----- 
From: "Bill Talbert" <btalbert at aeieng.com>
To: <bldg-sim at gard.com>
Sent: Friday, January 21, 2005 8:56 AM
Subject: [bldg-sim] Occupancy Sensors


> Does anyone have experience obtaining LEED credit for energy savings due
> to occupancy sensors? ASHRAE 90.1-1999 requires automatic lighting
> shutoff control (9.2.1.1) and occupancy sensors are one strategy for
> meeting this requirement. Addendum e to 90.1-2001 allows power
> adjustment percentages for the use of 'automatic lighting controls in
> addition to those required  for minimum code compliance.' If occupancy
> sensors are used for meeting the automatic shutoff control requirement
> with no additional shutoff controls provided, then my interpretation is
> that no energy savings credit can be taken. If anyone has a different
> interpretation or has had success achieving LEED credits, please let me
> know.  I am not aware of the USGBC adopting 90.1-2001 Addendum e yet,
> but if there is an opportunity to achieve savings through the use of
> occupancy sensors, it could be accomplished through the Exceptional
> Calculation Methods outlined in A90.1-1999 (11.5). Any assistance would
> be appreciated.
> Thanks,
>
>
> Bill Talbert, LEED AP
> Mechanical Engineer
> Phone: (608) 441-6677
> E-mail: btalbert at aeieng.com
>
> Affiliated Engineers Inc.
> 5802 Research Park Blvd.
> Madison, WI. 53719
> Tel. (608) 238-2616
> Fax. (608) 238-2614
>
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