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Choosing the Right Ventilation System

Approx. 10 min read

Introduction

Selecting the correct ventilation system is crucial for maintaining indoor air quality, energy efficiency, and regulatory compliance. With multiple options available — MVHR, PIV, dMEV, and cMEV — understanding the differences and benefits of each system helps ensure the right choice for your property type, budget, and occupancy.

System Comparison

MVHR (Mechanical Ventilation with Heat Recovery)

  • Operation: Centralised system supplying fresh air while extracting stale air, using a heat exchanger to recover up to 95% of heat.
  • Best for: New builds and airtight properties where energy efficiency is a priority.
  • Benefits: Energy savings, improved air quality, condensation control, and acoustic comfort.
  • Considerations: Higher upfront cost, ductwork installation, and regular maintenance.

PIV (Positive Input Ventilation)

  • Operation: Single-unit system introducing filtered air under slight positive pressure, pushing stale air out naturally.
  • Best for: Retrofit homes with condensation or mould issues, moderate airtightness.
  • Benefits: Low energy consumption, minimal disruption, continuous background ventilation.
  • Considerations: Limited energy recovery, effectiveness depends on property airtightness.

dMEV (Decentralized Mechanical Extract Ventilation)

  • Operation: Independent room-based extract fans remove moisture and pollutants from wet rooms.
  • Best for: Existing homes or small-scale retrofits where ducting is impractical.
  • Benefits: Targeted extraction, low running costs, simple installation and maintenance.
  • Considerations: Limited to wet rooms, may require multiple units.

cMEV (Continuous Mechanical Extract Ventilation)

  • Operation: Central fan extracts air from wet rooms via ducting, operating continuously with boost function.
  • Best for: New builds or homes needing discreet, centralised ventilation.
  • Benefits: Balanced extraction, low maintenance, low noise, regulatory compliance.
  • Considerations: Requires ducting and careful design to minimise pressure loss.

Factors to Consider When Choosing a System

  • Building Type and Airtightness – MVHR favours highly airtight properties; PIV and dMEV are suitable for less airtight homes.
  • Energy Efficiency Goals – MVHR provides heat recovery; other systems focus on moisture control.
  • Installation Complexity – Centralised systems require ducting; decentralized options are simpler to retrofit.
  • Maintenance Requirements – MVHR units need regular filter changes; PIV and dMEV require minimal servicing.
  • Occupancy and Lifestyle – High-humidity households benefit from humidity-controlled systems.
  • Budget – MVHR is higher cost upfront but offers long-term energy savings; other systems are more economical initially.

Compliance and Standards

All systems should meet Building Regulations Part F requirements for dwellings, with performance verified through:

  • Correct extraction and supply rates.
  • Noise level compliance.
  • Proper commissioning and documentation.

Flexivent Expertise

Flexivent provides professional guidance on selecting the most suitable ventilation system for your property. We deliver design, installation, and commissioning services, ensuring regulatory compliance and optimal performance for energy efficiency, comfort, and air quality. Contact Flexivent to evaluate and specify the right ventilation system for your home or project.