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What type of Airflow Extractor Fan do you need - what do the regulations say, what's the best fan?

  2010-08-25         admin         Advice » Ventilation Advice
Building Regulations Approved Document F: Ventilation (2010 Edition), stipulates the provision of adequate mechanical ventilation rates in non-habitable rooms such as toilets, bathrooms, shower rooms, kitchens and utility rooms in domestic dwellings.  Naturally, the Airflow extractor fans exceed these requirements in helping to combat the harmful effects of dampness and condensation, and by extracting airborne pollutants such as odours, cooking smells, humid and stale air, the potential hazards to the health of occupants and possible damage to the fabric of the building can be largely eliminated.

What do the regulations say?

The recommended volume of air extraction per room in the house recommended by the Building Regulations:
  • Toilet/sanitary accommodation: 6 l/sec (22 m3/hr);
  • Bathroom/shower room: 15 l/sec (54 m3/hr);
  • Kitchen adjacent to hob: 30 l/sec (108 m3/hr);
  • Kitchen without cooker hood: 60 l/sec (216 m3/hr);
  • Utility room: 30 l/sec (108 m3/hr);
Note: The Building Regulations guidelines for England and Wales state if the above rooms do not contain opening windows to allow rapid ventilation i.e. internal rooms, the requirement for mechanical ventilation will be satisfied if the fan has a 15 minute timer overrun. Please consult the approved document for guidance on open flue combustion appliances for complementary guidelines to mechanical ventilation and detailed information of alternative approaches.

Low Voltage Airflow Fans - Be Extra Safe

The Airflow range of SELV (Safety Extra Low Voltage) fans fully comply with the current IEE wiring regulations 17th edition detailing special requirements for bathrooms. These well proven fans use a 12 volt electrical supply(which means that the siting of the extractor fans is possible within the permitted splash zones of those using washing facilities). Note also that it is now possible to install a 230 volt, IPX5 rated fan with a dedicated RCD in splash zones. Consult the IEE 17th edition wiring regulations for full details.

What Type of Extractor Fan do I need?

Having considered the application of the ventilation required, it is important to select the correct type of fan to ensure that the requirement is met. It is not sufficient to fit just any extractor fan. It is important that the fan performs efficiently by extracting the minimum flow rate at the grille outlet as required by the latest Building Regulations. This is known as installed performance. Also, the number of bends and the length of duct attached to the fan will create resistance to flow that must be overcome to ensure adequate extraction.

You should first consider which type of fan will be best suited to provide quiet, efficient ventilation. This will be based on one of the following two general variants.

  1. The Airflow Centrifugal fans and Mixed Flow fans - these are are quiet, powerful and suitable extractor fans for wall, ceiling and window applications. They also work very efficiently against system resistance making them the perfect choice for ducted installations. Examples of such Airflow centrifugal / mixed flow fans:
  2. The Airflow Axial fans - these fans are ideal for through the wall and window applications. Providing high performance with a slim profile, they are suitable for use with ducting up to a maximum 2.5m ( 11m*) in length. Examples of such Airflow Axial Fans:
This article is the first part of Airflow's own guide / tips on: What Fan do I need and Where Should I site my Fan? Read the second part of this article(in the next article on the blog), or read the entire original article here. To purchase any Airflow Extractor fans, visit the Heating and Ventilation category - Ventilation systems.