• EBV - Building Ventilation
• Working - Office ventilation
• Learning - School ventilation
  • What makes a good indoor climate?
  • School ventilation
  • Principle means of control

Principal means of control

On-demand control is a way to reduce the energy consumption of ventilation units. By reducing the airflow when there is no-one in a room or building, or regulating the airflow to the required load, energy is saved (less fresh air to warm) and at the same time, the electrical consumption of the fan unit is reduced.

CAV principle – constant airflow

CAV (Constant Air Volume) constant airflow in the zone:

• Uniform requirements for ventilation
• Small changes in the number of people
• Small changes in the heat load
• Examples: copy room, passages, toilets, heating kitchen

VAV principle – variable airflow

VAV (Variable Air Volume) – control of airflow in two steps in the zone:

• Rooms that are used periodically
• The same number of people when in use
• The same heat load when in use
• Examples: classrooms (facing east), single-roomed office without sunlight

DCV principle – load regulation

DCV (Demand Controlled Ventilation) – variable individual regulation of airflow in a single zone

• Large changes in the number of people
• Large changes in the heat load
• Examples: staff room, classroom, IT room, school leisure organisation, Gymnasium, bath and changing room and conference rooms facing south

Economics and financials

Many older ventilation units installed in schools have no form of control. They run constantly, providing ventilation at times when there is no need to, which can waste significant energy.

On the other hand, it is all too easy to over-invest in control systems. It would not be sensible to install an extensive BMS system in a small school where there would be no possibility of exploiting the potential of the control system. Whenever possible, the energy savings gained from improved control system should always be weighed up against the extra initial investment. This requires a thorough assessment of the anticipated daytime running periods at the school.

There will always be a need to determine how many of the school's requirements can be met with the funds available.

Total cost of ownership = Purchase cose + Operating cost

EXHAUSTO documentation and guidance is designed to be used in every phase of a project - from planning and tendering through to installation, operation and servicing. As well as this project planning guide, more technical information is available in our individual product brochures or by contacting EXHAUSTO directly.