Implementing Demand-Controlled Ventilation...
Transcript of Implementing Demand-Controlled Ventilation...
page 1Implementing Demand-Controlled Ventilation Strategies© 2016 Trane, a business of Ingersoll-Rand.
ImplementingDemand-Controlled Ventilation Strategies
John Murphy, ASHRAE Fellow, LEED® AP BD+CApplications EngineerTraneIngersoll RandLa Crosse, Wisconsin
29 April 2016ASHRAE Region VI CRCMadison, Wisconsin
Implementing Demand-Controlled Ventilation Strategies2
ASHRAE Standard 62.1-2013
Section 6.2.7
6.2.7 Dynamic Reset. The system may be designed to reset the outdoorair intake flow (Vot) and/or space or ventilation zone airflow (Voz) asoperating conditions change.
6.2.7.1 Demand Control Ventilation (DCV)…
6.2.7.2 Ventilation Efficiency…
6.2.7.3 Outdoor Air Fraction…
Examples mentioned include:
• Variations in zone population(“demand-controlled ventilation” or DCV)
• Variations in ventilation efficiency due to changes in airflow(“ventilation optimization” or “ventilation reset”)
• Variations in OA fraction due to airside economizer operation(“VAV box minimum reset”)
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implementing DCV strategies
Agenda
• Requirements of ASHRAE Standard 90.1
• Common DCV technologies
• Implementing DCV is various types of systems
– Single-zone systems
– Dedicated (100%) outdoor-air systems
– Multiple-zone recirculating systems
Implementing Demand-Controlled Ventilation Strategies4
ASHRAE Standard 90.1-2010 (mandatory requirement)
Demand-Controlled Ventilation
6.4.3.9 Ventilation Controls for High-Occupancy Areas.Demand control ventilation (DCV) is required for spaces larger than 500 ft2
and with a design occupancy for ventilation of > 40 people per 1000 ft2 offloor area and served by systems with one or more of the following:
a. an air-side economizer,
b. automatic modulating control of the outdoor air damper,
or
c. a design outdoor airflow > 3000 cfm.
Exceptions:
a. Systems with exhaust air energy recovery complying with Section 6.5.6.1.
b. Multiple-zone systems without DDC of individual zones communicating with acentral control panel.
c. Systems with a design outdoor airflow < 1200 cfm.
d. Spaces where the supply airflow rate minus any makeup or outgoing transfer airrequirement is less than 1200 cfm.
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• Correctional waiting room
• Lecture classroom
• Lecture hall
• Multi-use assembly
• Restaurant dining room
• Cafeteria / fast food dining
• Bars, cocktail lounge
• Conference / meeting
• Break room
• Telephone / data entry
• Transportation waiting
• Auditorium seating area
• Place of religious worship
• Courtroom
• Legislative chambers
• Lobby
• Spectator area
• Disco / dance floor
• Gambling casino
• Stage / studio
>40
peo
ple
/1000
ft2
Implementing Demand-Controlled Ventilation Strategies6
ASHRAE Standard 90.1-2013 (mandatory requirement)
Demand-Controlled Ventilation
6.4.3.8 Ventilation Controls for High-Occupancy Areas.Demand control ventilation (DCV) is required for spaces larger than 500 ft2
and with a design occupancy for ventilation of ≥ 25 people per 1000 ft2 offloor area and served by systems with one or more of the following:
a. an air-side economizer,
b. automatic modulating control of the outdoor air damper,
or
c. a design outdoor airflow > 3000 cfm.
Exceptions:
1. Systems with exhaust air energy recovery complying with Section 6.5.6.1.
2. Multiple-zone systems without DDC of individual zones communicating with acentral control panel.
3. Systems with a design outdoor airflow < 750 cfm.
4. Spaces where > 75% of the space design outdoor airflow is required formakeup air that is exhausted from the space or transfer air that is requiredfor makeup air that is exhausted from other space(s).
5. Correctional cells, daycare sickrooms, science labs, beauty and nail salons,and bowling alley seating.
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impact of90.1-2013
• Correctional waiting room
• Lecture classroom
• Lecture hall
• Multi-use assembly
• Restaurant dining room
• Cafeteria / fast food dining
• Bars, cocktail lounge
• Conference / meeting
• Break room
• Telephone / data entry
• Transportation waiting
• Auditorium seating area
• Place of religious worship
• Courtroom
• Legislative chambers
• Lobby
• Spectator area
• Disco / dance floor
• Gambling casino
• Stage / studio
• Correctional waiting room
• Daycare
• Classroom (ages 5-8)
• Classroom (age 9+)
• Lecture classroom
• Lecture hall
• Computer lab
• Media center
• Music / theater / dance
• Multi-use assembly
• Restaurant dining room
• Cafeteria / fast food dining
• Bars, cocktail lounge
• Conference / meeting
• Lobby / pre-function
• Break room
• Reception area
• Telephone / data entry
• Transportation waiting
• Auditorium seating area
• Place of religious worship
• Courtroom
• Legislative chambers
• Lobby
• Museum / gallery
• Spectator area
• Disco / dance floor
• Health club / aerobics room
• Gambling casino
• Stage / studio
≥ 2
5p
eo
ple
/1000
ft2
>40
peo
ple
/1000
ft2
Implementing Demand-Controlled Ventilation Strategies8
ASHRAE Standard 90.1-2010 (prescriptive requirement)
Ventilation Optimization
6.5.3.3 Multiple-Zone VAV System Ventilation Optimization Control.Multiple-zone VAV systems with DDC of individual zone boxes reporting to acentral control panel shall include means to automatically reduce outdoor airintake flow (Vot) below design rates in response to changes in systemventilation efficiency (Ev) as defined by ASHRAE Standard 62.1, Appendix A.
Exceptions:
a. VAV systems with zonal transfer fans that recirculate air from other zoneswithout directly mixing it with outdoor air, dual-duct dual-fan VAV systems,and VAV systems with fan-powered terminal units.
b. Systems required to have the exhaust air energy recovery complying withSection 6.5.6.1.
c. Systems where total design exhaust airflow is more than 70% of totaldesign outdoor air intake flow requirements.
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implementing DCV strategies
Agenda
• Requirements of ASHRAE Standard 90.1
• Common DCV technologies
• Implementing DCV is various types of systems
– Single-zone systems
– Dedicated (100%) outdoor-air systems
– Multiple-zone recirculating systems
Implementing Demand-Controlled Ventilation Strategies10
Demand-Controlled Ventilation (DCV)
An energy-saving control strategy that responds to theactual “demand” (need) for ventilation in a zone by varyingthe rate at which outdoor air is delivered to that zone.
cfm required = cfm/person number of people
local code,ASHRAE 62.1
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ASHRAE Standard 62.1-2013, Section 6.2.7.1
Demand-Controlled Ventilation
6.2.7.1 DCV shall be permitted as an optional means of dynamic reset.Exception: CO2 -based DCV shall not be applied in zones with indoor sourcesof CO2 other than occupants or with CO2 removal mechanisms, such asgaseous air cleaners.
6.2.7.1.1 The breathing zone outdoor airflow (Vbz) shall be reset in response tocurrent occupancy and shall be no less than the building component(Ra × Az) of the DCV zone. Note: Examples of reset methods or devices includepopulation counters, carbon dioxide (CO2) sensors, timers, occupancyschedules, or occupancy sensors.
6.2.7.1.2 The ventilation system shall be controlled such that at steady-state itprovides each zone with no less than the breathing zone outdoor airflow (Vbz)for the current zone population.
6.2.7.1.3 The current total outdoor air intake flow with respect to the coincidenttotal exhaust airflow for the building shall comply with Section 5.9.2.
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Time-of-Day (TOD) Schedule
• Scheduling function of the BAS is used to define theamount of outdoor air required in a zone for each hour… based on estimated population
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0
50
100
150
zo
ne
po
pu
lati
on
,P
z
midnight 6 a.m. noon 6 p.m. midnight
example: high school cafeteria
Occupancy/Ventilation TOD Schedule
200 estimated Pz
each hour
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People Counters
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Occupancy Sensor / Motion Detector
• Sensor is used to determine if people are present
– Simple, binary input
• When a zone is occupied:
– Zone ventilation setpoint is set to design outdoor airflow
• When a zone is unoccupied:
– Zone ventilation setpoint is reduced to“building” ventilation airflow (Ra × Az)
Implementing Demand-Controlled Ventilation Strategies16
example: conference room
Occupancy Sensor
• Floor area (Az) = 300 ft2
• Design population (Pz) = 10 people
• Required outdoor airflow at design population
Vbz-design = Rp Pz + Ra Az
= 5 cfm/p 10 people + 0.06 cfm/ft2 300 ft2
= 68 cfm
• Required outdoor airflow at zero population
Vbz-standby = 5 cfm/p 0 people + 0.06 cfm/ft2 300 ft2
= 18 cfm
6.2.7.1.1 The breathing zone outdoor airflow (Vbz) shall be reset in response tocurrent occupancy and shall be no less than the building component (Ra × Az) of theDCV zone.
8.3 Systems shall be operated such that spaces are ventilated in accordance withSection 6 when they are expected to be occupied.
ASHRAE Standard 62.1-2013 (see official interpretation 62.1-2010-4)
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“occupied-standby” mode
Addendum P to ASHRAE 62.1-2013
6.2.7.1.1 For DCV zones in the occupied mode, breathing zone outdoor airflow(Vbz) shall be reset in response to current population.
6.2.7.1.2 For DCV zones in the occupied mode, breathing zone outdoor airflow(Vbz) shall not be less than the building component (Ra x Az) for the zone.
Exception: Breathing zone outdoor airflow shall be permitted to be reducedto zero for zones in occupied-standby mode for the occupancy categoriesindicated in Table 6.2.2.1 provided that airflow is restored to Vbz wheneveroccupancy is detected.
Section 3 Definitions
occupied mode: when a zone is scheduled to be occupied
occupied-standby mode: when a zone is scheduled to be occupied andan occupancy sensor indicates zero population within the zone
addendum P to ASHRAE Standard 62.1-2013
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physical activity level, MET
0 1 2 3 4 5
0.5
0
1.0
1.5
2.0
CO
2p
ro
du
cti
on
,L/
min off
ice
work
sle
epin
g
walk
ing
lightm
achin
ew
ork
very light moderatelight
Source: ASHRAE Standard 62.1-2013, Figure C-2
CO2 Sensor
• Production of CO2 isrelated to the person’slevel of activity (MET).
• Therefore, CO2 can beused as a "tracer gas"for occupancy.
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CO2-Based DCV
0
200
400
600
800
1000
1200
1400
1600
CO
2co
ncen
trati
on
,p
pm
steady state conditions
time
CO2 outdoors
15 cfm/p
20 cfm/p
10 cfm/p
CO2 indoors
Implementing Demand-Controlled Ventilation Strategies20
Mass Balance: CO2-Based DCV
CO
2co
ncen
trati
on
,p
pm
time
CO2 indoors
COA = 350 ppm
Cspace = 1050 ppm
Cspace – COA = N / VOA
N = CO2 generation rate, cfm/personVOA = ventilation rate, cfm/person
0
200
400
600
800
1000
1200
1400
1600
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CO2-based DCV
Setpoints Vary by Application
• CO2 generation rate (N) varies with activity level– Refer to Appendix C of ASHRAE 62.1
• Ventilation rate (VOA) differs by space type andcfm/person varies as zone population changes
• Outdoor CO2 concentration (COA) varies by location
– Most designers use a one-time reading from the site ora conservative value from historical local data
"Unless combustion fumes are present, the outdoor CO2
concentration in most locations seldom varies more than 100 ppmfrom the nominal value."
ASHRAE Transactions, 1998
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implementing DCV strategies
Agenda
• Requirements of ASHRAE Standard 90.1
• Common DCV technologies
• Implementing DCV is various types of systems
– Single-zone systems
– Dedicated (100%) outdoor-air systems
– Multiple-zone recirculating systems
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DCV in a Single-Zone System
SASAOAOA
RARAEAEA
space
CO2
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implementing DCV in a single-zone system
ASHRAE 62.1 User’s Manual (Appendix A)
Example: University lecture classroom• Floor area (Az) = 1000 ft2
• Peak population (Pz) = 65 people
• CO2 generation rate (N*) = 0.0105 cfm/person(light desk work)
• Outdoor CO2 concentration (COA) = 350 ppm
For this occupancy classification, Table 6.2.1.1of ASHRAE Standard 62.1-2013 requires:
• Rp = 7.5 cfm/person
• Ra = 0.06 cfm/ft2
* N, cfm/person = MET 0.0084 for average adult population(Standard 62.1-2010 User’s Manual, p. 158)
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implementing DCV in a single-zone system
Example: University Lecture Classroom
1) Calculate breathing-zone outdoor airflow (Vbz)for both design population and with zero people
Vbz = Rp × Pz + Ra × Az
Vbz-design = 7.5 × 65 + 0.06 × 1000 = 550 cfm (8.5 cfm/p)
Vbz-DCVmin = 7.5 × 0 + 0.06 × 1000 = 60 cfm (>68 cfm/p)
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implementing DCV in a single-zone system
Example: University Lecture Classroom
2) Calculate steady-state indoor CO2 concentration (Cs)for both design population and with zero people
Cs = COA + N / ( Vbz / Pz )
Cs-design = 350 + 0.0105 / (550 cfm / 65 people) = 1600 ppm
Cs-DCVmin = 350 + 0.0105 / (60 cfm / 0 people) = 350 ppm
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implementing DCV in a single-zone system
Example: University Lecture Classroom
Vbz-design = 550 cfm
indoor CO2 concentration, ppm
Vbz-DCVmin = 60 cfm
ou
tdo
or
air
flo
w,cfm
set position of OA damper to bring in60 cfm when indoor CO2 equals 350 ppm
set position of OA damper to bring in550 cfm when indoor CO2 equals 1600 ppm
For single-zone systems, Vot = Voz = Vbz/Ez (assumes Ez = 1.0)
Cs-design = 1600 ppmCs-DCVmin = 350 ppm
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implementing DCV in a single-zone system
Control Coordination Issues
SAOAOA
EAEA RA
1. Economizer operation should override DCV2. Don’t forget about building pressure control
space
CO2P
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implementing DCV strategies
Agenda
• Requirements of ASHRAE Standard 90.1
• Common DCV technologies
• Implementing DCV is various types of systems
– Single-zone systems
– Dedicated (100%) outdoor-air systems
– Multiple-zone recirculating systems
Implementing Demand-Controlled Ventilation Strategies30
implementing DCV in a dedicated OA system
OA Delivered Directly to Each Zone
SAlocalHVAC unit
CACA
EA
VAV
dedicatedOA unitOA
VFD
CO2
RA CA
SA
CO2
RA
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implementing DCV in a dedicated OA system
Control Coordination Issues
• Requires pressure-independent OA dampers forany non-DCV zones also
• Requires variable airflow at the dedicated OA unit(added benefit of fan energy savings)
• Don’t forget about building pressure control!
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implementing DCV strategies
Agenda
• Requirements of ASHRAE Standard 90.1
• Common DCV technologies
• Implementing DCV is various types of systems
– Single-zone systems
– Dedicated (100%) outdoor-air systems
– Multiple-zone recirculating systems
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implementing DCV in a multiple-zone recirculating system
1) CO2 Sensor in Every Zone?
SASA
OAOA
RARAEAEA
space
space
CO2
CO2
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implementing DCV in a multiple-zone recirculating system
1) CO2 Sensor in Every Zone?
• Requires a CO2 sensor in every zone– CO2 level doesn’t change much in many of the zones
– Non-critical zones will always be over-ventilated
– Increases installed cost, maintenance, and risk of energy waste
• Requires BAS to poll all sensors and then determinerequired OA damper position
• Requires method to ensure minimum outdoor airflow
6.2.7.1.1 The breathing zone outdoor airflow (Vbz) shall be reset in responseto current occupancy and shall be no less than the building component(Ra × Az) of the DCV zone.
ASHRAE Standard 62.1-2013
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implementing DCV in a multiple-zone recirculating system
2) CO2 Sensor in Common Return Duct?
SASAOAOA
RARAEAEA
space
space
Under-ventilates some zones while over-ventilating others
CO2
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implementing DCV in a multiple-zone recirculating system
2) CO2 Sensor in Common Return Duct?
6.2.7.1.2 The ventilation system shall be controlled such that at steady-state itprovides each zone with no less than the breathing zone outdoor airflow (Vbz)for the current zone population.
ASHRAE Standard 62.1-2013
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implementing DCV in a multiple-zone recirculating system
3) DCV at Zone Level + Ventilation Reset
lounge restroom
storage office
office conference rm computer roomreception area ele
vato
rs
vestibule corridor
CO2
CO2
OCC
OCC
TOD TOD
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implementing DCV in a multiple-zone recirculating system
3) DCV at Zone Level + Ventilation Reset
• Use all zone-level DCV approaches,each where it best fits
– CO2 sensors: densely-occupied zones with highly-variable population
– Occupancy sensors: low-density offices or densely-occupied zones where population varies only minimally
– Time-of-day schedules: zones with predictable patterns
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implementing DCV in a multiple-zone recirculating system
3) DCV at Zone Level + Ventilation Reset
CO2 OCC
SA RA
CO2TOD TODOCC
• Current required outdoor airflow (Voz)(TOD schedule, OCC sensor, CO2 sensor)
• Current primary airflow (Vpz)• Current OA fraction (Zpz)
communicating VAV controllers
AHU or rooftop unit withflow-measuring OA damper
• Reset intake airflow (Vot)
Building Automation System• Find highest OA fraction (Zpz)• Calculate current system
ventilation efficiency (Ev)• Calculate current system
intake airflow (Vot)
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implementing DCV in a multiple-zone recirculating system
3) DCV at Zone Level + Ventilation Reset
• Saves energy during partial occupancy
• Lower installed cost, less maintenance, and morereliable than installing a CO2 sensor in every zone
– Use zone-level DCV approaches where they best fit(CO2 sensor, occupancy sensor, time-of-day schedule)
– Combine with ventilation reset at the system level
• Earn LEED EQc1: Outdoor Air Delivery Monitoring
• Monitor CO2 concentrations within all densely occupied spaces ...
• Provide a direct outdoor airflow measurement device capable ofmeasuring the minimum outdoor air intake flow ...
IEQ credit 1, LEED-NC (v2009)
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implementing DCV in a multiple-zone recirculating system
4) DCV + VAV Box Reset + Ventilation Reset
CO2
SA RA
CO2TOD TODOCC
• Current required outdoor airflow (Voz)(TOD schedule, OCC sensor, CO2 sensor)
• Current primary airflow (Vpz)• Current OA fraction (Zpz)• OA fraction limit (max Zpz)
communicating VAV controllers
AHU or rooftop unit withflow-measuring OA damper
• Reset intake airflow (Vot)
Building Automation System• Find highest OA fraction (Zpz)• Calculate current system
ventilation efficiency (Ev)• Calculate current system
intake airflow (Vot)
OCC
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CO2-Based DCV for Multiple-Zone HVAC Systems
ASHRAE Research Project 1547
• Compares various control sequences
• Further enhances control sequencesand setpoints for multiple-zonerecirculating ventilation systems
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Implementation of RP-1547 CO2-Based DCV Control Sequences
ASHRAE Research Project 1747
“Valid logic was developed in RP-1547, but it is not readily implemented inreal control systems.”
“This project will develop practical control sequences, then test them in areal-world building environment with a commercial-grade DDC system.”
RFP for ASHRAE Research Project 1747
• Project began in September 2015… with expected completion by February 2017
Implementing Demand-Controlled Ventilation Strategies44
Seventhwave (2015) field study of DCV in Minnesota
DCV Control Sequences Implemented
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Seventhwave (2015) field study of DCV in Minnesota
Measured/Calculated Energy Savings
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Seventhwave (2015) field study of DCV in Minnesota
Findings From Recommissioning
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Seventhwave (2015) field study of DCV in Minnesota
Most Critical DCV Commissioning Steps
• During design, verify that designer has defined:
1. Control sequence
2. CO2 setpoint(s)
3. OA flow limit(s)
4. Sensor location(s)
5. Airflow measurement
• During installation, verify CO2 sensors are calibrated
• After occupancy, verify that system performs accordingto the sequence, for at least a week of operation
• Ensure that the owner is trained, and understands whatthe sensors should do and why they do it
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implementing DCV strategies
Summary
• ASHRAE Standard 62.1 allows dynamic reset ofventilation air as operating conditions change
• ASHRAE Standard 90.1 is requiring DCV in moretypes of spaces
• Consider CO2-based DCV in densely-occupied zoneswith widely-varying population
• Use other DCV technologies (occupancy sensors,time-of-day schedules) where they make sense
• Combine DCV with ventilation reset in a VAV systemto avoid the need to sense CO2 in every zone
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implementing DCV strategies
Further Reading• American Society of Heating, Refrigeration and Air-Conditioning Engineers,
Inc. 2011. 62.1 User’s Manual. Atlanta, GA: ASHRAE.
– Appendix A: CO2-Based Demand-Controlled Ventilation
– Appendix B: Ventilation Reset Control
• Murphy, J. 2005. “CO2-Based Demand-Controlled Ventilation withASHRAE Standard 62.1,” Trane Engineers Newsletter (ADM-APN017-EN).
• Seventhwave. 2015. “Energy Savings from Implementing and EnergySavings from Implementing and Commissioning Demand Control Ventilation.”
• Stanke, D. 2006. “Standard 62.1 System Operation: Dynamic Reset Options”,ASHRAE Journal (December): pp. 18-32.
• Stanke, D. 2010. “Dynamic Reset for Multiple-Zone Systems,”ASHRAE Journal (March): pp. 22-35.
• ASHRAE Research Project 1547. CO2-Based Demand-Controlled Ventilationfor Multiple-Zone Systems. January 2014.
• ASHRAE Research Project 1747 (in progress). Implementation ofRP-1547 CO2-based DCV for Multiple-Zone Systems in DDC Systems.