Meeting latest ventilation requirements

Ruth MacEachern, Product Manager at EnviroVent, looks at how to ensure compliance with ventilation requirements in dwellings as part of improving indoor air quality.

“In the last 20 years, ventilation has increasingly been recognised for the vital part it plays in delivering a healthy home.

Ruth MacEachern, Product Manager at EnviroVent, looks at how to ensure compliance with ventilation requirements in dwellings as part of improving indoor air quality. efficient ventilation systems into modern dwellings is crucial in order to maintain good indoor air quality, enhance the health of occupants and retain the structural integrity of a property. 

The latest update to Approved Document F, which came into effect in June 2022, brought about several key modifications that have reshaped the approach to ventilation in both new and existing dwellings.

Prior to the 2022 update, Approved Document F was a single document that primarily addressed ventilation in new dwellings. It provided limited guidance on non-residential buildings and was supplemented by the Domestic Ventilation Compliance Guide. This often led to confusion and inconsistencies in interpretation. 

The revised Approved Document F comprises two volumes: Volume 1: dwellings and Volume 2: non-dwellings.

In addition, the Domestic Ventilation Compliance Guide has been integrated into the main document, streamlining the information and making it more accessible to professionals in the field.

Updated building regulations

Some of the most significant changes in the 2022 update included:

  • Renaming of ventilation methods for clarity.
  • Increased whole dwelling ventilation rates.
  • Modified requirements for background ventilation.
  • Introduction of specific guidance for existing dwellings.
  • Enhanced focus on indoor air quality and volatile organic compounds (VOCs).

These changes reflect a more holistic approach to ventilation, acknowledging the interconnected nature of air quality, energy efficiency and occupant health.

To ensure compliance with Approved Document F, it is important to understand the main types of ventilation systems available and their respective strengths and limitations.

Natural ventilation with intermittent extract fans

Natural ventilation with intermittent extract fans (formerly known as System 1) relies on a combination of background ventilators (such as trickle vents) and intermittent extract fans in wet rooms. 

While it offers simplicity and low initial costs, it may struggle to meet the increased ventilation rates required by the updated regulations, particularly in more airtight dwellings.

Continuous Mechanical Extract Ventilation (MEV and d-MEV)

Previously referred to as System 3, MEV systems provide continuous low-level extraction from wet rooms, with the option for boost speeds when required. Decentralised MEV (d-MEV) operates through individual fans in each wet room, offering greater flexibility in installation and maintenance.

MEV systems have many benefits, including providing a consistent level of background ventilation, a reduced risk of condensation and mould growth and also lower energy consumption compared to intermittent extraction. A reduced amount of background ventilation is required in habitable spaces to ensure sufficient cross-ventilation across the property.

Mechanical Ventilation with Heat Recovery (MVHR)

MVHR systems, formerly known as System 4, offer the most comprehensive approach to whole-house ventilation. These systems extract stale air from wet rooms and supply fresh, filtered air to habitable rooms, while recovering heat from the extracted air to improve energy efficiency.

The benefits of MVHR systems are that they offer excellent control over indoor air quality and can provide significant energy savings in well-insulated homes.  They can also effectively filter incoming air, reducing allergens and pollutants.

Although the initial outlay with MVHR may be higher than for MEV systems, they do offer an enhanced level of ventilation performance, ensuring very good levels of indoor air quality throughout a property.

Meeting the challenges 

Meeting the requirements of Approved Document F presents several challenges for specifiers of ventilation systems for new homes or renovations. However, working with ventilation specialists means any obstacles can be overcome.

The increased whole dwelling ventilation rates specified in the 2022 update require a more rigorous approach to system design and specification. For a one-bedroom property, the minimum ventilation rate has risen from 13 l/s to 19 l/s, a significant increase that may require upgrading to more powerful or efficient systems.

As buildings become more airtight to improve energy efficiency, the risk of poor indoor air quality increases. Striking the right balance between conserving energy and providing adequate ventilation is crucial.

There are a number of ways to address these challenges.  Firstly, MVHR systems provide heat recovery which helps to minimise energy loss, as well as filtered incoming air.  It is also possible to implement demand-controlled ventilation to adjust airflow based on occupancy and humidity levels.  

When MVHR is installed, it is essential to ensure proper sealing of ductwork to prevent air leakage, which is best done by using a NICEIC approved ventilation installer. 

In addition, on handover of a property, it is important to educate occupants of the importance of not blocking or disabling ventilation systems.

Noise considerations

One of the primary concerns with mechanical ventilation systems is noise levels inside the property. Approved Document F now includes guidelines for minimising noise from ventilation systems, recognising the impact of acoustic disturbance on occupants.

To mitigate noise issues, many specifiers select low-noise fans and MVHR units.  It is also possible to utilise sound-absorbing materials within the ductwork of an installation.  Many units, such as our energiSava range, offer anti-vibration mounts and are manufactured using appropriate materials to reduce sound transmission.  

Another factor which should not be overlooked is the need to ensure accurate sizing of systems to avoid over-ventilation and its associated noise.

Airflow measurement

Accurate measurement of airflow rates is essential to verify that the installed system meets the required performance standards. The regulations specify that:

  • Airflow must be measured at each room terminal.
  • Measurement devices must have a proprietary hood attachment.
  • Equipment must have an accuracy of ±5% and be calibrated within the past 12 months.
  • Results must be recorded on the commissioning sheet.

For whole-house mechanical ventilation systems, accurate balancing is crucial to ensure that the correct airflow is achieved in each room. This process involves adjusting dampers and fan speeds to achieve the desired air distribution throughout the dwelling.

Once the installation and commissioning process is complete, the ventilation manufacturer/installer provides in-depth documentation to both the building control body and the occupants of the home. 

Compliance with Approved Document F means that ongoing maintenance and monitoring are essential to ensure continued performance and adherence to regulations.

In addition, with the increasing recognition of the harmful impact of Volatile Organic Compounds within domestic settings, the 2022 update places greater emphasis on indoor air quality and the control of VOCs. While specific limits are provided as guidance rather than strict requirements, the inclusion of this information highlights the growing importance of these factors in building design and ventilation.

Future homes

As the industry moves towards fully implementing the Future Homes Standard in 2025, ventilation requirements are likely to become even more stringent. The construction industry needs to keep abreast of regulatory changes to ensure ongoing compliance, energy efficiency and optimal performance.

By collaborating with ventilation manufacturers on the design of systems to meet the latest ventilation requirements, architects can create healthy, comfortable and energy-efficient living spaces that meet both regulatory requirements and occupant needs.

As buildings become increasingly airtight, mechanical ventilation systems play a vital role in enabling increasingly airtight buildings to benefit from high levels of indoor air quality for the long term.

Effective ventilation system design can go a long way to address the potential challenges in new homes, with the result being improved indoor air quality, better energy efficiency and reduced carbon emissions.”