Ventilation

A Comprehensive Guide to different types of ventilation

Ventilation is a crucial aspect of maintaining a healthy and comfortable indoor environment. It helps in regulating air quality, controlling moisture levels, and maintaining a comfortable temperature within a property. This guide delves into various ventilation systems, elucidating their pros, cons, and typical applications.

Purge Ventilation (e.g., standard bathroom vents)

Pros:

  • Energy-Efficient: High vapour load per warm air lost to the outside.
  • Low Installation Cost: Generally less expensive to install.
  • Targeted: Good for wet rooms and areas of high moisture production.

Cons:

  • Poor Installation Risks: If not installed correctly, such:
    • flexible ducting, especially if unextended, which reduces airspeed increasing the risk of leakage and degradation over time, compared to rigid ducting,
    • back-flow shutters becoming trapped,
    • exit airspeed should be tested to ensure the exit airflow is close to or exceed:
      • 15 l/s for a bathroom,
      • 30 l/s for a kitchen extractor hood or
      • 60 l/s for a kitchen extractor on an adjacent wall.
  • Maintenance: Fans can lose air speed over time due to dirt build-up.
  • Overrun: Need to be run until all excess vapour is removed, typically 30 minutes for a bathroom.

Typical Properties: Any residential or commercial property, particularly those with wet rooms.

Positive Input Ventilation (PIV)

Pros:

  • Ease of Use: Simple systems to operate.

Cons:

  • High Installation Cost: More expensive than Purge but less than whole-house systems with heat recovery.
  • Untargeted: Blows out warm air of average vapour load, requires additional wet room extractor fans.
  • Energy Inefficient: Due to loss of warm air.

Typical Properties: Larger residential buildings or smaller commercial buildings where there’s no control over vapour production.

Heat Recovery Ventilation

Pros:

  • Air Quality: Good for maintaining indoor air quality.

Cons:

  • High Installation and Running Cost: Expensive to both install and run.
  • Untargeted to Vapour Production: Not suitable for wet rooms.
  • Energy Inefficient: Air is alternately blown in and out, causing heat loss, some energy is recovered, but the vapour load is low, making it overall energy inefficient.

Typical Properties: New properties, complete renovations, large commercial buildings like hotels.

Whole Property with Heat Recovery

Pros:

  • Comprehensive: Covers the entire property and automated.

Cons:

  • Very High Installation Cost and complex ductwork: Only justified in new builds, large renovations, or commercial properties.
  • High maintenance and sometimes running costs.
  • Hard to design efficiently: Poor design can lead to energy inefficiency, build up of vapour and consequential mould in poorly ventilated rooms and condensation within the system itself, leading to leaks.

Typical Properties: New builds, complete renovations, or large commercial buildings.

Stacks

Pros:

Cons:

  • Limited Control: Cannot easily control airflow or target specific areas.

Typical Properties: Older homes and buildings without modern ventilation systems.

Passive Vents

Pros:

  • Low Cost: Inexpensive to install.

Cons:

  • Uncontrolled: Cannot target specific areas or control airflow.

Typical Properties: Older homes and smaller commercial buildings.

Dehumidifiers

Pros:

  • Energy-Efficient: No heat is lost to the outside.
  • Targeted: Useful for areas with specific moisture issues.

Cons:

  • Running Cost: Although efficient, they do consume electricity.

Typical Properties: Any, but particularly useful for properties with zone heating or insulation imbalance.

Hybrid Systems – Mix of the above, especially adding the use of a dehumidifier

Pros:

  • Efficient and Pragmatic: Useful in properties with insulation or heating imbalance.

Cons:

  • Complexity: Requires careful design to ensure each component complements the others.

Typical Properties: Almost all residential and commercial properties, particularly those with complex moisture issues.

Conclusion

Designing the right ventilation system is a meticulous task that entails understanding the unique needs of a property. Hybrid systems, despite their complexity, often provide a pragmatic and efficient solution, especially in properties facing complex issues like insulation imbalance, heating imbalance, or zones of untargeted vapour production. Ensuring proper design, installation, and maintenance are the keys to an effective, energy-efficient ventilation system that caters to both the comfort and health of the occupants.

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