System 1: Intermittent Extract Fans & Background Ventilation
This system incorporates background ventilators, such as trickle ventilators or standard hole-in-the-wall ventilators, coupled with extract fans in wet rooms. The background ventilators supply fresh air to habitable spaces, while the extract fans remove odors and excessive humidity from wet areas.
- Simple System design and installation process
- Extract Fans connected to light switches allow occupants to control ventilation
- Effortless Installation
- Lacks “intelligent” sensors found in System 3 (DCV)
- Single Facade dwellings may require additional backgrounde ventilators
- Extract Fans may generate noise nuisance
System 2: Passive Stack Ventilation and Background Ventilators
A passive stack is a non-mechanical approach to ventilation, where air vents are located in various locations around the dwelling. Using the principle of convection, currents allow the movement of air through the ducts.
With passive stack system, airflow rates are very much weather dependant. Strong gusts can cause over ventilation and surges in ventilation rates; little or no wind may result in inadequate ventilation.
The system is completely uncontrolled. Large amounts of cold air can be drawn into the building, increasing the heat load.
- No running costs unless mechanical backup is necessary
- Quiet Operation
- Ductwork can be discreetly concealed
- Challenging to replicate system design for standard dwelling formats.
- Effectiveness varies with weather conditions, requiring occasional mechanical backup, especially during warm periods.
- Increased heat loss and efficiency fluctuations based on weather conditions.
System 3: Demand Control Ventilation (DCV)
Demand Control Ventilation (DCV) automatically adjusts ventilation based on actual demand using suitable sensors. It can be triggered by occupancy, moisture, or air-quality sensors that detect carbon dioxide or other pollutants.
A central fan maintains a constant air pressure in the system, adjusting ts speed as required. Humidity-sensitive extracts in wet rooms open or close based on room humidity levels. When an extract opens, causing a pressure drop, the fans speed up to return to the target pressure. The more extracts that open, the higher the extraction rate becomes.
- Continuous ventilation at predetermined rates
- Single Penetration to the building’s external fabric (central extract)
- Controlled Ventilation system independent of outside wind and pressure
- Perceived higher running costs
- Potential noise issues, requiring careful design considerations
- Ductwork installation requires qualified professionals, adding to the overall cost.
System 4: Continuous Mechanical Supply & Extract with Heat Recovery
Mechanical Ventilation with Heat Recovery (MVHR) continously extracts stale moist air from wet rooms while supplying fresh air directly to habitable rooms. The unique feature of MVHR is the use of heat exchangers to transfer heat energy from the outgoing stale air to preheat the incoming fresh air.
Stale, humid air is continuously extracted from wet room and passed through a heat exchanger before being exhausted. Fresh cold air from outside is drawn in, warmed by the heat exchanger, and then supplied to the habitable rooms through sealed ductwork. The supply and extract rates are balanced to maintain comfortable air pressure and minimise draughts.
- Controlled ventilation for optimal airflow and comfort, reducing heat demand and minimising heat loss.
- Pre-heated fresh air for enhanced comfort and energy efficiency
- Limiting noise pollution.
- Enhances energy efficiency rating and complies with regulations, filtering incoming air for improved air quality.
- Requires qualified installers for ductwork installation.
- Incompatible with open fires; requires a room sealed stove.
- Requires commissioning using an anemometer.
- Filter maintenance, requiring periodic cleaning or replacement.
By understanding the different types of ventilation systems available, you can make an informed decision about the best approach to achieve optimal air quality, comfort, and energy efficiency for your home or building.