Building Regulation Basics for Domestic Ventilation

In this article we'll take a look at some helpful tips to point you in the right direction when planning the installation or replacement of a domestic extractor fan unit.

The aim of the building regulations in regards to ventilation of domestic properties (Part F) is to protect the health of the occupants of the building by providing adequate ventilation.

Without adequate ventilation, mould and internal air pollution might become hazardous to health. This means extracting water vapour and other indoor air pollutants from areas where they are produced in significant quantities - for example, kitchens, utility rooms and bathrooms. Each of these areas has a specific minimum extraction rate determined by these factors.

The purpose of this article is to give a basic overview to help you choose a suitable extraction unit that complies with these regulations. All these tips are correct to comply with the current regulations at the time of the publication of this article (March 2023).

While the regulations are there to be followed for new builds, it is important to know that installing non-compliant units can affect rental properties and the re-sale of properties. However, even if you are not planning to rent or sell your property, complying to these regulations when replacing or installing an extractor fan is important for the health of the occupants in the property.

Let’s begin by looking at the minimum extraction rates needed for the different spaces in a property to meet these regulations.

In the table below, each of the spaces that require extraction ventilation in a domestic setting have been included. These spaces are fairly self-explanatory; but for clarity, Sanitary Accommodation is defined as WCs, urinals or toilets without shower or bath. The table shows the minimum extraction rates in both litres per second and metres cubed per hour (rounded up to the nearest whole number) for both intermittent fans and continuous flow fans. In the case of the continuous flow fans, the rate given is the minimum extraction rate for the fan on boost setting rather than the trickle flow setting:

Looking at kitchen ventilation, there are two options here which are dependent on whether or not there is a cooker hood installed and whether the hood extracts to the outside or only filters and recirculates the air within the kitchen.

If no cooker hood is installed or the hood installed only recirculates filtered air into the kitchen, then additional extraction is needed. A dedicated intermediate kitchen fan, inline fan or continuous flow fan needs to be installed. Intermediate extraction must give a minimum of 60l/s of extraction, whereas a continuous fan must extract a minimum of 13l/s on its boost setting to qualify.

However, If there is a cooker hood installed that vents to the outside, then no additional extractor fan is needed so long as the cooker hood extracts a minimum of 30l/s, the hood is mounted directly above the hob and the height of the hood is in line with either the manufacturer’s instructions or, if not specified, between 650mm and 750mm above the hob surface.

On the subject of positioning, the regulations state that any installation needs to offer easy access for maintenance such as replacing filters (if applicable), cleaning ducting and the fan unit, general maintenance or replacing the unit. This is worth bearing in mind, especially if you are ceiling mounting a fan unit or installing an inline fan. Quite often, fans can be installed in ceiling voids and when the ceiling is replaced, the unit is sealed in with zero access. This becomes an expensive issue when a unit needs to be replaced, cleaned or just having settings adjusted. Ensuring that there is an access hatch or access from your loft space to the installation will save having to have your ceiling rebuilt and redecorated!

It is also worth noting if you are looking to install a new fan rather than replacing an existing unit, that the regulations also state that an extractor fan needs to be installed as high as is practicable in the room but no more than a maximum of 400mm below the ceiling. This is worth taking into account if you have a high ceiling and are interested in installing a fan with a built in pull cord.

You can see the full 2021 Edition Building Regulations 2010 Approved Document F for Domestic Ventilation here.