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Building Regulations

Approved Document F details the requirements for ventilation in new dwellings as part of Building Regulations. Ventilation is in place for people inside dwellings, and the Approved Document sets out the airflow rates based on;
  • dwelling size
  • number of bedrooms
  • occupancy

There are a number of ventilation strategies that are detailed ranging from intermittent (ON and OFF) to continuous (low level trickle and boost) options which also include energy efficient technology. It's overall aim is to remove pollutants and deliver a good consistent level of indoor air quality.

In addition, the Domestic Ventilation Compliance Guide provides guidance and on system design, installation and commissioning.

Unsure what you need to comply? Call our technical team on 033 0223 4180 

Download Approved Document F

Approved Document F

    

Building Regulations

Ventilation Rates

Approved Document F sets out the airflow requirements for new build dwelling and extensions/additions to existing buildings.

Airflow are calcualted from Table 5.1a and Table 5.1b for both intermittent and continuous ventilation rates.

Continuous ventilation is common in new build properties to help deliver consistent, low energy and quiet ventilation to the dwelling e.g. dMEV, MEV and MVHR. 

Building Regulation Table 5.1

    

Building Regulations

Ventilation Strategies

The Building Regulations Approved Document F outlines 4 standardised ventilation methodologies for homes offering a range of benefits depending on build type and occupant requirements;

System 1
Intermittent Extract and Background Ventilation

  • Extract fans in wet rooms e.g. Kitchen/Bathroom
  • Fans are 'ON' or 'OFF' dependent on controls
  • Supply/Replacement air provided via trickle ventilators in windows

System 3
Central Mechanical Extract Common in new build

  • Continuous extract ventilation
  • Central system ducted to wet rooms or decentralised in each room
  • Replacement air provided via trickle ventilators in windows/walls

System 4
Mechanical Supply & Extract Ventilation with Heat Recovery Common in new build

  • Balanced supply and extract ventilation - no requirement for background ventilators
  • Centrally mouted system ducted to all rooms in dwelling
  • Heat Recovery recovers and reuses up to 90% of heat that would otherwise have been lost

System 4 Heat Recovery Ventilation

    

What's impacting ventilation in new dwellings?

Overheating

Increased insulation levels combine with rising temperatures has meant issues with overheating in homes

Thermal modelling will identify the risk of overheating and planning restrcitions may introduce additional airflow known as purge ventilation.

Purge ventilation can have signifcant impact on the approach to ventilation as increased duct sizes and larger MVHR units may be required to deliver the higher airflow rates. See how HRV approach purge ventilation with our unique PVHR™

Noise

Density planning and brownfield development means new dwellings located close to busy roads 

Noise assessments results will require acoustic dB reduction in noise transfer through openings in the facade of the dwelling from ventilation.

Acoustic ventilation options such as acoustic trickle ventilators or  MVHR which require very few penerations in the external facade may be considered as the best and most cost effective approach to the ventialtion strategy.

Indoor Air Quality

Outdoor air impacts indoor air - in polluted areas non-openable windows may be a requirement

Air Quality assessments will identify hazardous pollutants and advise of additional filtration for ventilation systems under planning.

Filtration of diesel particulates will require carbon filters which can be fitted within the ducting network of the MVHR Heat Recovery unit.  Consideration for access, filter replacement and routine maintenance needs to be considered.

If you are designing a new ventilation system or need some advice - please call us on 033 0223 4180 or emails enquiries@hrv-group.com

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