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Part F - System 1

System 1: Intermittent extract fans and background ventilators

System 1System 1 is traditionally the most commonly used system in the UK.

Where can it be used?

System 1 is suitable for use in houses and many flats or apartments with multi fašades. In some circumstances, it can be difficult to comply with System 1, especially in dwellings with a single façade. For new build or refurbishment.

How does it work?

The System comprises of background ventilators, usually trickle ventilators fitted to windows and extract fans fitted in moisture producing areas or "wet rooms" such as kitchens and bathrooms.

The background ventilators provide the whole building ventilation and also supply air to the intermittently operated extract fans which provide the extract ventilation removing odours and excessive humidity.

How do we determine ventilation rates?

Guidance on minimum provisions for extract and whole dwelling ventilation is set out in Tables 5.1a and 5.1b (in combination with Table 5.2a) of Approved Document F (Ventilation) 2010. Note that it includes additional guidance for dwellings with only a single façade.

The whole building ventilation rate for background ventilators is determined by a number of factors:

  • Dwelling floor area
  • Number of bedrooms
  • Number of occupants
  • Number of storeys
  • Number of façades

What benefits does it offer?

  • Simplicity
  • Operation familiar to most occupants
  • Straightforward installation
  • Occupant control

What difficulties could we encounter?

  • Perceived high running costs, though usually not actual
  • Noise potential of low quality or poorly installed fans
  • Single façade dwellings require additional background ventilators fitted at low level

For an overview of Titon's trickle ventilators click here.

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