/, Contextual, Cooling, Heating, HVAC, Long term, Offices, Owners, Physical environmental, Psychological, Social/2.2.22 Convert the constant volume system to a Variable Air Volume (VAV) system

2.2.22 Convert the constant volume system to a Variable Air Volume (VAV) system

2.2.22 Convert the constant volume system to a Variable Air Volume (VAV) system


In tertiary buildings a CAV (Constant Air Volume) system is normally used for ventilation and air-conditioning. In order to keep the room temperature in required level during the summer period quite high airflow rates and higher amounts of energy for heating and distribution of air are needed. By changing the system to VAV operation, considerable energy savings can be achieved.


  • The technology saves heating and cooling energy along with fan energy

  • There is virtually no need to retrofit, demolish, or install ductwork or terminal units

  • Less system down time and disturbance to building occupants than there would be with a full VAV system retrofit

  • Improve occupant comfort and productivity


  • The system as a whole must be adapted to the new way of operation

  • Each terminal unit has an air valve and possibly a coil which require electrical and/or pneumatic service

  • VAV requires the use of diffusers with proven distribution characteristics over a wide range of air flows

  • Potential indoor air quality problems if proper precautions are not taken

Economic assessment

Investment cost: high.

Payback: between 2 to 15 years depending on the type of building and whether the system operates continuously or for 12 hours a day, 5 days a week.

References and best practices

  • Energy savings by changing Constant Air Volume systems (CAV) to Variable Air Volume systems (VAV) in existing office buildings. Experience from a plant reconstruction based on a new supply air terminal device concept: http://www.enerma.se/wp-content/uploads/2017/02/article_final_version_mlm_ljr.pdf

Image gallery


Environment or playable world:

  • Residential

  • Academic

  • Offices

  • All

Carried out by:

  • Public building users

  • Owners

  • Operators

  • All

Reduce consumption of:

  • Heating

  • Cooling

  • DHW

  • Lighting

  • Electric devices

Type of driver:

  • Physical environmental

  • Contextual

  • Psychological

  • Physiological

  • Social

Time framework:

  • Short term
  • Long term

Type of measure:

  • Envelope
  • HVAC
  • DHW
  • Lighting
  • Electrical devices
  • Other
Print to PDF
Print this page