Achieving Demand Control Ventilation Based on Occupancy

a measurable difference!

Achieving Demand Control Ventilation Based on Occupancy

Effi cient venŸ laŸon is a key challenge for schools, requiring a balance between maintaining indoor air quality (IAQ) and opŸ mizing energy efficiency. At South Lafourche High School and Thibodaux Middle School in Louisiana, fl uctuaŸng occupancy levels—parŸcularly in classrooms and gymnasiums—highlighted the need for a more innovaŸve approach to venŸ laŸon. Tasked with enhancing the HVAC systems at these schools, Castagnos Goodwin Utley (CGU) Engineers implemented a cu« ng-edge soluŸon to ensure both energy savings and compliance with ASHRAE standards.

Background on the Schools

South Lafourche High School, located in Galliano, Louisiana, serves students from several coastal communi•es. Established in 1966, the school accommodates over 1,100 students in grades 9–12. AL er a two-story addi•on in 2000 and a renova•on of the outdoor air handling units in 2016, the district sought to ensure the building’s ven• la• on system could meet new demands—especially with many rooms remaining empty most days—without was• ng energy.

Thibodaux Middle School serves grades 6–8 in nearby Thibodaux, Louisiana. Spaces such as the gymnasium, where occupancy can shiL rapidly during events or physical educa•on classes, posed a unique challenge for maintaining proper IAQ without incurring high energy costs.

The VenƟ laƟ on Challenge

Proper venŸ laŸon is crucial in schools to protect the health of students and staff and ensure occupant comfort. Proper pressur-izaŸon is also crucial, especially in humid climates, to ensure no biological growth or moisture damage. However, tradiŸ onal CO2DCV oLen falls short in large-volume spaces and spaces where occupancy changes quickly. This is due to sampling errors, CO2 sensor lag in response, or sequences that do not consider the venŸ laŸon rates. The result can be over-venŸ laŸ on, wasŸ ng energy, ineffi cient venŸ laŸ on, impacŸng air quality, and not complying with the codes.

Robert Utley of CGU Engineers recognized the limita•ons of CO2based systems, par•cularly in dynamic spaces like gymnasiums. Addi•onally, compliance with ASHRAE Standard 62.1, which sets ven• la•on requirements based on actual occupancy, required a more precise approach.

There were several key ques• ons raised:

• How can ven• la•on systems adapt to real-•me changes in occupancy?
• Can airflow be dynamically managed to reduce energy consump•on while ensuring compliance with IAQ standards?

IntroducƟon to EBTRON

Paul Trammel, Sales Engineer at Product Engineering, introduced Robert Utley to EBTRON’s advanced airfl ow measurement solu•ons. Recognizing their poten•al, Paul invited Robert to EBTRON’s Bring-A-Guest (BAG) event. This event provided Robert with hands-on technical demonstra•ons and in-depth knowledge about innova• ve solu•ons for real-• me airfl ow management. The event also facilitated collabora•on with HVAC professionals, including engineers, architects, and contractors, helping Robert develop the best strategy for the schools’ unique challenges.

ImplemenƟng a Dynamic Airfl ow SoluƟ on

CGU Engineers implemented a strategy combining occupancy counters and airflow measurement devices at both schools. This approach allowed ven• la•on rates to be dynamically adjusted in real-•me, ensuring op•mal IAQ while minimizing energy con-sump• on.

• Occupancy Counters: Installed at entrances to classrooms and gyms, these devices provided real-•me data on the number of occupants in each space.
• Airflow Measurement StaŸons: These staŸons allow precise control over venŸ laŸon rates and limit the minimum and maximum venŸ laŸon required for IAQ and energy effi ciency.

In gymnasiums, where occupancy could shiL from a handful of individuals to hundreds during events, this system was parŸ cularly eff ecŸve. By integraŸng the soluŸon with the building automaŸ on system (BAS), the HVAC system automaŸcally adjusts venŸ laŸ on and temperature based on occupancy.

“The integra•on of EBTRON’s occupancy counters and airflow measurement devices allowed us to create a system that dynamically adjusts ven• la• on based on real-•me occupancy,” said Robert Robert Utley Utley, Principal at Castagnos Goodwin CGU Engineers Utley Engineers. “This approach ensured compliance with ASHRAE standards while signifi cantly reducing energy consump•on. It was par• cularly impac•ul in areas like gymnasiums, where occupancy levels fl uctuate drama• cally, enabling us to maintain comfort and air quality without unnecessary energy costs.”

Key Results

South Lafourche High School

• Installed 54 occupancy counters across classrooms and shared spaces.
• Adjusted ven• la•on rates dynamically, ensuring no under- or over-ven• la•on while reducing energy waste.
• Conducted annual system accuracy checks to maintain performance.

Thibodaux Middle School

• Installed eight occupancy counters in key areas, including the gymnasium.
• The gym now adjusts venŸ laŸon based on real-Ÿ me occupancy, effi ciently accommodaŸ ng fl uctuaŸons from a few students to the enŸre school populaŸ on.
• Addi•onal energy savings were achieved through a Variable Refrigerant Flow (VRF) system.

The Benefits of Real-Time VenƟ laƟ on

U•lizing occupancy counters in South Lafourche and Thibodaux schools demonstrated the importance of integra• ng real-• me data into ven• la•on strategies. Relying on CO2-DCV without real-•me measurement of airflow or a fi xed ven• la•on rate leads to poten•al IAQ problems or was•ng energy in spaces with unpredictable occupancy. Combining occupancy coun•ng with precise airflow measurement ensured both schools could:

• Provide adequate ven• la•on for health and comfort
• Avoid the cost of over-condi•oning outside air
• Maintain compliance with IAQ standards

By tailoring ven• la•on to actual occupancy in real-• me, buildings can achieve significant energy savings without compromising air quality or occupant comfort. Airflow measurement devices and occupancy counters helped both schools become more sustainable by ensuring the health of students and staff and validaŸ ng compliance with ASHRAE standards.

Broader ApplicaƟ ons

This case illustrates the use of counŸng people for demand control venŸ laŸon and climate control. However, these counters could also be used for traffi c counŸng in restrooms and dining areas, especially within the educaŸon, restaurants, and nursing home central areas for people counŸng and cleaning opŸ miza-Ÿon. In addiŸon to controlling proper venŸ laŸ on, real-Ÿ me data can be used to schedule cleaning staff effi ciently, thereby minimizing labor costs while maintaining high standards.aintaining high standards.

Thermal Imaging Occupancy Counter

• Dual sensor diff erenŸal thermal imaging
• Bi-direc• onal coun• ng
• Typically be©er than ±5% of the actual popula•on or 3 people, whichever is greater
• Temperature (recommended limits): 65 to 85⁰F [18.3 to 29.4⁰C]
• Humidity: 5 to 95%

High Sensor Density MulƟ point Airflow and Temperature Measurement Monitoring Device

• Thermal dispersion technology
• Supports up to 16 Sensor Nodes
• NIST-traceable Calibra• on
• Velocity-weighted Temperature
• Airflow: ±2% of reading
• Temperature: ±0.15⁰F [0.08⁰C]

EBTRON.,Inc.

1663 Highway 701 South

Loris, South Carolina 29669 www.EBTRON.com

a measurable difference!