Ventilation Best Practices in UK Housing

Adequate ventilation is fundamental to healthy indoor environments. It removes moisture, pollutants, and stale air while providing fresh air for occupants. In UK housing, ventilation requirements are set out in Building Regulations Approved Document F, with specific provisions for different room types and building strategies.

Building Regulations Overview

Approved Document F (2021 edition, effective June 2022) sets minimum ventilation rates for dwellings. Key requirements include:

• Extract ventilation in wet rooms: Kitchens (30 l/s intermittent or 13 l/s continuous), bathrooms (15 l/s or 8 l/s)
• Background ventilation: Trickle vents or equivalent for whole-dwelling ventilation
• Purge ventilation: Openable windows (1/20th of floor area) for rapid air exchange

Ventilation Strategies

System 1: Natural Ventilation

Background ventilators (trickle vents) plus intermittent extract fans in wet rooms. Relies on natural pressure differences to move air. Cost-effective but dependent on occupant behaviour and weather conditions.

System 3: Mechanical Extract Ventilation (MEV)

Continuous mechanical extract from wet rooms with background ventilators for air supply. More reliable than natural ventilation, doesn't rely on occupants opening windows. Common in social housing retrofits.

System 4: Mechanical Ventilation with Heat Recovery (MVHR)

Balanced supply and extract with heat exchanger recovering warmth from outgoing air. Most energy-efficient but requires proper installation and maintenance. Increasingly specified in new-build and deep retrofit projects.

Common Ventilation Problems

• Blocked or closed trickle vents: Often closed by occupants to reduce draughts
• Failed extract fans: Motors burn out, switches fail, ductwork disconnects
• Inadequate ductwork: Long runs, excessive bends, undersized ducts reduce airflow
• Dirty filters: MVHR systems require regular filter replacement
• Occupant behaviour: Windows never opened, extract fans switched off

Monitoring Ventilation Effectiveness

CO2 levels are an excellent proxy for ventilation adequacy in occupied spaces:

• Below 800 ppm: Good ventilation
• 800-1200 ppm: Acceptable, could be improved
• 1200-1500 ppm: Inadequate ventilation, action needed
• Above 1500 ppm: Poor ventilation, urgent attention

Elevated CO2 often correlates with elevated humidity, as both indicate insufficient air exchange.