We explain Demand Controlled Ventilation

There are two different kinds of demand controlled ventilation, Variable Air Ventilation (VAV) and Demand Controlled Ventilation (DCV). As both terms imply, these are ventilation solutions that manually or automatically regulate the airflow to meet the exact need at a given time. If a room is empty, supply of air is reduced and if another room is full of people, the system will increase the air volume in that area. In this guide we will explain how it works.

Save energy without compromising on indoor climate

The reason for adjusting the airflow is simple. It is not necessary to supply the same air volume to rooms when they are empty as when they are crowded. With Constant Air Ventilation (CAV), the airflow is constant and often set to a higher volume to avoid low air supply when the room is filled. Of course, this means that an unnecessary amount of air is supplied when the room is completely empty. The solution to this is called demand controlled ventilation. VAV and DCV are two types of demand controlled systems that allow adjusted air flows which help to save energy.

One purpose - two different systems

VAV and DCV systems fulfill the same purpose, to adapt ventilation and air conditioning to varying levels of people and activity in the premises. In general, it is possible to achieve greater energy savings and better indoor climate with a more advanced system. However, there are of course applications where simpler systems work well. What, then, are the differences and benefits of the two options respectively?

VAV - Variable Air Volume

  • Less advanced demand control where the air flow may vary over an operating time and may be adapted to e.g. temperature or air quality
  • Meet the requirements for most simpler projects, such as preschools and smaller schools
  • Normally implies lower investment costs compared to DCV
  • Often provides good energy savings compared to CAV

DCV - Demand Controlled Ventilation

  • Advanced demand management that adjusts air flows and temperature depending on the activity and occupancy of the premises e.g with different operating cases
  • Greater opportunity to adapt comfort according to different customer needs
  • Most often air and waterborne products may be combined for a complete indoor climate system
  • A clearly contributing installation to reach high classifications in various building certification programs, for instance BREEAM, WELL and LEED
  • Great opportunities to save energy as the system is highly adaptable

→ Read more in our blog DCV & VAV - What is the difference?

Advanced, not complicated

It is of great importance to keep the premises ventilated correctly for the best productivity and performance, health and well-being. However, in most types of buildings, the level of activity varies around the clock, meaning that empty rooms are far too often ventilated as if they were full.

The most advanced system to cope with varied activity and occupancy is DCV. In terms of demand controlled ventilation, advanced means a smart system that is technically well developed and that doesn’t add complexity. The smart system enable extra opportunities to maximize comfort, avoid unnecessary energy consumption and thereby minimise cost.

Three basic functions with DCV

  • The air is directed to where the actual need is
  • Always stepless
  • Always supervised

DCV regulates based on

  • Temperature - to keep the right temperature in the room
  • Air quality - to ensure an optimal indoor climate for performance, health and well-being
  • Humidity – to make certain the building is not exposed to mold-promoting moisture content
  • Occupancy - to save energy when the room is empty

Since the ventilation is based on peoples’ presence and their needs, the system runs on "economy speed" as soon as the demands decrease in the building

→ See our solutions for demand-driven systems


Why demand controlled ventilation?

Investigations in i.a. schools show how the attendance rate in different types of spaces is generally low, which means that a system that adjusts ventilation and air conditioning according to actual needs can save up to 80% of the fan energy and 40% of the heating and cooling energy. In addition, the system usually requires smaller ventilation units and cooling machines, which reduces the investment cost. This is also applicable to many other types of premises, e.g. offices, housing and hotels.

Attendance in the classroom during school hours
TeknDr. Dennis Johansson, Presence in Buildings - Measurements and Estimates, 2010

It is clear that it is not sustainable from an energy and environmental perspective to ventilate at full power around the clock. It is not necessary even during the most active hours of the day. There are systems that help keeping the energy consumption low, the economic savings high and the indoor climate still excellent. A simpler VAV system may be fully sufficient in smaller projects where the requirements are not particularly advanced and the cost of investment a decisive factor. For projects where the expectations on the indoor climate is higher and the building possibly larger there is the DCV system. To be certified according to any green or well-being based building program, the latter more advanced DCV systems are required.

The occupant

The past few decades have meant major changes in where and how most of us spend our days, but humans basically function the same way they did thousands of years ago. By starting from the human being when designing our indoor climate systems, it is possible to keep comfort high, which positively affects both performance, wellness and long-term health.

What is the relationship between occupants and interiors?

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