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Indoor air quality guidance in Approved Document F

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Indoor air quality guidance in Approved Document F

By Ruth MacEachern

Product Manager

Oct 30, 2022

Combating climate change is an issue that is at the forefront of the minds of campaigners, policymakers, and property developers alike. As the government attempts to meet targets and enforce change, there is an ever-changing list of rules and regulations that developers and engineers must consider. This mountain of regulations, amendments and red tape can often seem overwhelming, however, in this article we are going to help you understand the changes to Approved Document F and how you can ensure compliance.

What is Approved Document F?

Approved documents, often simply referred to as ‘building regulations’, are guidance documents issued by the government with a view to ensuring correct and safe practices within the construction industry in England. The Future Homes Standard, renamed the Future Homes and Buildings Standard in December 2021, is the set of rules set to be introduced by the government in 2025, aiming to ensure that new homes produce fewer carbon emissions. In preparation for these new changes, the government amended the 2010 Building Regulations in June of 2021, including notable changes to Approved Document F, governing ventilation and indoor air quality. The document has now been split into two separate volumes, one governing dwellings (Volume 1), and buildings other than dwellings  (volume 2). 

Summary of the key requirements and changes to document F

The main aim of Approved Document F is to “protect the health of occupants of the building by providing adequate ventilation”. This includes controlling and limiting the formation of mould and the presence of air pollutants within the internal atmosphere, while also regulating air flow/ventilation rates within a dwelling. The amendments introduced in 2021 not only provide a clearer structure, but also outline a number of changes with a view to establishing a new ventilation standard. Below is an overview of the most significant changes:

1: Terminology changes: new terminology has been adopted when referring to methods of ventilation, in place of the numbering of the various systems.

  • Natural Ventilation with Intermittent Extract Fans and Background Ventilators, rather than “System 1”
  • Passive Stack Ventilation, previously referred to as “System 2”, has been removed
  • Continuous Mechanical Extract Ventilation (MEV and d-MEV) in place of “System 3”
  • Mechanical Ventilation with Heat Recovery (MVHR) instead of “System 4”

2: An increase in whole dwelling ventilation rates (rates are determined based on the floor area of a room). By comparing calculations to a table provided in the new version of Document F, minimum ventilation rates can be determined for a room, based on the number of occupants.

In a one-bed property, this amounts to an increase of 6 l/s per occupant -  a significant rise that will certainly affect decision-making when choosing a suitable product to comply with the new ventilation standard.

3: Background ventilation requirements in relation to Continuous Mechanical Extract Ventilation (MEV and d-MEV) have been adjusted, where previously this wasn’t always a requirement if the property was leaky in terms of air permeability, this is now a mandatory requirement, and would require significant planning and renovation work if these were retrofitted.

4: There has been an addition of minimum numbers of background ventilators based upon the number of bedrooms in the property. Previously, this was calculated using floor area and bedrooms and was rather complex. This provides an easy to follow minimum set standard to increase the background ventilation levels in dwellings.

5: Requirements have also become more stringent with regard to mechanical ventilation in particularly airtight buildings (buildings with an air permeability rating of less than 5). These changes include the following:

  • The background ventilation requirement has now increased from a value of 2,500 mm2 to 4,000 mm2 per habitable room
  • The total number of background ventilators in the dwelling must not be fewer than the number of bedrooms, plus an additional two
  • For properties with natural ventilation, the rates and methods for calculating ventilation requirements are now determined on a ‘per room’ basis

6: Tables providing guidance in relation to indoor air quality and volatile organic compounds are now provided, identifying potential contaminants, exposure limits, and times, along with advice on the appropriate action to be taken should the specified levels be exceeded.

If these requirements seem like a lot to take in, the requirements governing non-residential buildings, as outlined in Volume 2 of the approved document, go even further, with new regulations and specifications concerning CO2 monitoring, the filtration of recirculated air, the minimisation of pollutants, airflow rates in common spaces, VOC testing strategies,  and maintenance to fans, filters, duct work etc.

Many good reasons to comply

While the motivation behind the government’s future homes standard pathway is undoubtedly an attempt to double down in the battle against climate change, there are many tangible benefits to ensuring compliance in your new build or renovation. Effective ventilation will drastically improve indoor air quality, bringing with it a host of health benefits for occupants. What’s more, the financial benefits of an effectively ventilated home are significant, both regarding ongoing heating costs and future saleability. For these reasons alone, it is certainly worth engaging with the new standards and regulations and their impact on your own project planning.

Volume 1 of the revised Approved Document F is available to read for yourself, here:

We can help you understand building regulations

If you feel at all overwhelmed by all this talk of compliance, ventilation rates, and indoor air quality requirements, you are certainly not alone. Fortunately, the experts at EnviroVent  have a sound grasp of all technical aspects relating to the new and amended building regulations. They will be happy to discuss compliance, product selection, and the sizing of your installation to suit your specific project.