Demand Controlled Ventilation

Demand Controlled Ventilation (DCV) is a system of ventilation that automatically adjusts air flow rates into buildings in response to actual air quality. The systems are controlled by a central unit containing sensors linked via ducting into each room to be ventilated. Each sensor controls mechanical ventilation equipment that regulates the air flow. This has two key benefits versus traditional systems: indoor air quality should be enhanced, and energy usage should be lower due to the ventilation system only being switched on when needed, rather than running continuously.

Suitable for:

Demand Controlled Ventilation is particularly suitable for new build properties and major renovations.

The system requires ducting to be installed between each room and the control unit, which is normally situated in a loft space (see picture to the right of a Renson Health box system). It can be installed as a retrofit but a careful plan for locating the duct-work is required.

Each property requires trickle vents in the windows to allow the air to enter the building.

Technical information

Over the last decade, the drive to create energy efficient buildings has resulted in increasing levels of insulation and much tighter air tightness levels.

Unfortunately this can prevent houses from ‘breathing’, and pollutants can accumulate affecting indoor air quality. Indoor air is permanently polluted, with many causes:

  • People themselves (e.g. CO2, water vapour, odours)

  • Human activity (e.g. cooking, bathing, going to the toilet)

  • Building materials (e.g. radon and formaldehyde)

  • Production processes (e.g. dust, smells and VOC)

The build-up of moisture-laden air can cause damp homes. The unhealthy indoor climate created by damp almost doubles the risk of developing asthma. Unfortunately 30.7 million Europeans had asthma in 2004.

A DCV system set up to maximise internal air quality adapts the airflow rate to the actual pollution load, which often is proportional to the occupancy. For example, all the rooms in an office building or in a school are almost never occupied at the same time. It is most unlikely that the peak level of occupancy occurs simultaneously in all occupied rooms. The bigger the variation between the minimum and peak loads, the more energy savings can be expected with a DCV system based on air-quality control.

The benefits which occupants of homes with good indoor air quality are:

  • We sleep better & feel better / more active during the day

  • Better concentration, performance

  • Less susceptibility to allergies

  • Asthmatics suffer less

  • Better “smells” in the house / improved air movement

  • Less pollution

The DCV control modules can be programmed based on the type of room. The installer can indicate whether the room is a wet or dry room. The control modules are then set to the required flow rate per room and will communicate with the motor unit to determine the optimum total flow rate of all wet and dry rooms. This minimises the risk of errors during set-up and is a major timesaver. Total adjustment time will be limited to an average of 12 minutes.

Some manufacturers will provide a choice of decorative aluminium vent covers for the ducting exits into rooms.

Typically a system would involve sensors in the control box that measure the air flow through the ducting from the relevant rooms. The sensors monitor pollutants, moisture, CO2 levels and VOCs and control flaps in the ducting to optimise the level of extracted air.

To help property owners understand how their air indoor quality is performing, some manufacturers provide wall-mounted touch display screens.

With some systems it is possible to extend the system to include a motorless cooker extraction hood in your kitchen. The kitchen module can be activated using the TouchDisplay and/or KitchenTimer. When switching to cooking mode, the ventilation system can use its full extraction capacity in the kitchen, while the airflow in the other rooms remains at a minimum level. If the kitchen mode is not used, your extractor hood will provide the basic ventilation (basic ventilation 12-75 m3/h - 250m3 cooking function/h).

Why Ventilate? The secret to Healthy Living

This video from DCV manufacturer, Renson, explains the health benefits of ventilating properties.

Related Products


Hints & Tips

Make sure you consider your ventilation solution at design stage, in order to ensure your windows have trickle vents.

DCV installations can be much simpler than for Mechanical Ventilation with Heat Recovery (MVHR). The entire system can be automatically calibrated, achieving the appropriate flow rate for each control module, regardless of the length and type of the ducting.

Designing an optimum layout is vital for a Demand Controlled Ventilation system to ensure optimum ducting positioning and providing clear guidelines for installers. SBS can provide a design solution.

Ventilation Design & Estimation

It is important to properly layout the ducting designs for each Ventilation system.

If you could use some impartial expert advice, try our renewable heating design and estimation service. We use full REVIT-based software linked to Building Information Modelling, can show a 3D representation of the ducting, and offer a fast turnaround.