Ventilation Design: Part F Compliance for Non-Domestic Buildings

Proper ventilation is critical in a workplace setting. It helps deliver improved air quality, reduces the impact of airborne viruses, and contributes to employee health and wellbeing. It also helps to protect the fabric of a building and its contents through the removal of excess moisture. 

Whilst the Workplace Health, Safety and Welfare Regulations 1992 cover legal obligations for workplace ventilation, it is the Building Regulations Part F that govern the correct design, installation and commissioning of ventilation systems. 

What Are Part F Building Regulations?

As a section of the Building Regulations in England and Wales, the purpose of Part F is to ensure that adequate ventilation exists within buildings of regular occupancy. Practical guidance on how to achieve this is laid out in Approved Document F (or more specifically for non-domestic buildings, Approved Document F: Volume 2)

This covers the three main types of building ventilation:

  • Extract ventilation: this provides high rates of ventilation in spaces where water vapour and/or pollutants are likely to be released (e.g. extraction fans installed in bathrooms and kitchens).
  • Purge ventilation: this is a controlled form of room ventilation which can remove high concentrations of water vapour or pollutants resulting from occasional activities (e.g. paint fumes). This can be provided via natural means such as open windows, or via a mechanical ventilation system.
  • Whole building ventilation: this is continuous ventilation at a relative low rate, designed to provide a supply of fresh outdoor air and to dilute, disperse and remove water vapour and pollutants not removed by extract ventilation. 

 

These three approaches to ventilation, along with continuous monitoring of indoor air quality, are combined to form an effective ventilation strategy under Part F approved guidance.

Compliant Ventilation Design in Non-Domestic Buildings

The specific design of any ventilation project will depend on the purpose of the building or space involved. But to illustrate how such a project might look in practice, we can take the example of an office building, as this particular building type is covered extensively in Approved Document F. 

The guidance sets out clear performance parameters for different spaces within an office building using the three approaches to ventilation outlined above:

Office Extract Ventilation

Minimum extraction rates are provided for five specific areas:

  • Sanitary accommodation
  • Bathrooms
  • Washrooms
  • Food and beverage prep areas
  • Rooms housing printers and photocopiers used for more than 30 minutes per hour

What those minimum extraction rates are can vary. For example, in food preparation areas, intermittent extraction rates can sit between 15 and 60 litres per second depending on the location of the extractor, and the appliances within the space (a microwave only requires a lower extraction rate than a hob for example).  

Office Whole Building Ventilation

For occupiable rooms, the ventilation system needs to be designed to meet whichever is higher between:

  • A total rate of 10 litres per second per person
  • 1 litre per second per m2 floor area

Common office spaces such as corridors should be provided with either:

  • Natural ventilation via openings (e.g. windows) with a total area of at least 1/50th of the common space floor area.
  • Mechanical ventilation designed to provide a supply of outdoor air at 0.5 litres per second per m2 of the common space floor area. 

Office Purge Ventilation

All offices must also have purge ventilation designed to provide at least 4 air changes per hour. Purge ventilation must be directed outside and not recirculated to any other part of the building. 

Alongside the minimum requirements above, an office ventilation design project must also take into consideration the following:

Noise: including ensuring mechanical systems are sized so fans do not need to operate in a high mode when providing standard background ventilation.

Controls: providing controls to allow ventilation rates in each room to be adjusted and that in rooms without windows, extract ventilation operates for at least 15 minutes after an occupant has left.

Recirculation: ensuring an adequate rate of outdoor air can be achieved in all areas of the building without recirculation unless the system features specific filtering capabilities, such as HEPA filters.

External Pollution: this applies to buildings located near to sources of external pollution such as a main road, and requires considered design of ventilation intakes and exhausts. 

As you can see from this basic example, ventilation design is a complicated process. It takes a lot of expertise to ensure Part F compliance, and that only escalates as the requirements of a project become more complex. 

At Loughborough Air Conditioning, we have years of experience in the design, installation and commissioning of effective ventilation systems, and are able to self certify work under Building Regulations Part F as part of the BESCA Competent Person Scheme.

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