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Guide to Fans and Ventilation

A Guide to Fans and Ventilation

Why do we need fans at home?

Poor ventilation affects over 4.5 million British homes and is estimated to cost over £500 million per annum. Without adequate ventilation, the air can become stale and condensation can occur, resulting in a risk of respiratory illness and general poor health.

What causes stale air?

Stale air can be caused by a number of factors including cooking smells, smoking, bathroom odours, damp and a general lack of ventilation.

What causes condensation?

Condensation is caused when steam from the kitchen or the bathroom settles on cooler surfaces around the house.

Where should a fan be located?

Fans can be beneficial if placed in bathrooms, toilets, kitchens and utility rooms. A fan should be sited in a window or wall – farthest from the source of air replacement. This avoids short-circuiting the airflow. The fan should be as high as possible in the window or wall – closest to any smells or steam, however not directly above eye-level grills or cooker hoods. When installing a fan into a bathroom - The Institute of Electrical Engineers require that the fan must be out of reach to prevent it being touched by any person using the bath or shower. It must be well away from any water so that there is no likelihood of the fan being splashed.

However, at AllAboutElectrics, we stock ‘Safety Extra Low Voltage’ fans which can be fitted in an area where splash is a possibility. This is because there is no chance of electric shock being caused by this extra safe fan.

Installing a fan…

…in a ceiling: Check there are no joists, pipes or cables above the area where the fan is going. If it is likely that steam and/or condensation will occur, ducting must be used (unless venting directly to the outside). In some locations, condensation can run backwards towards the fan. If this is likely – a condensation trap must be installed as close to the fan as possible. Ducting or soil pipe should be insulated if installing in an unheated roof void, in order to minimise the formation of condensation. Calculate the route that the ducting will take and the length that is required. An external grille will be needed to match the ducting diameter.

…in a wall: It is important to check that there are no buried pipes or cables and that the outside wall is not obstructed by any pipes.

…in a window: We recommend you have the hole pre-cut by a professional glazier. If you are not sure of the weight or type of glass you will need for your fan to be installed – your glass supplier will advise you. This is essential where fans are to be installed in roof light situations.

Types of fan operation

  • Standard – these are controlled by a remote switch e.g. through a light switch.
  • Timer Model – these often have a built-in adjustable time delay operated by the light switch.
  • Pull-cord Model – these come with a built-in pull-cord switch.
  • Humidity Controlled model – these are designed to turn the fan on as humidity rises and off again as the humidity drops again.
  • P.I.R. model – these have a sensor in to detect movement so that the fan will turn off if somebody enters the room and off when the room is vacated.

Examples of types of fans

  • Axial Fans – These are designed to move air over short distances.
  • Centrifugal Fans – These are designed to move air over longer distances.
  • Humidistat Controls – These measure and control relative humidity. Humidistat controls are designed to turn the fan on as humidity rises and off again as the humidity drops again. It will measure the humidity 24 hours a day – therefore preventing the formation of mould and decreasing the amount of condensation issues.
  • Low Voltage Fans – These are for use in bathrooms. The Institute of Electrical Engineers state that only electrical equipment of below 12 Volts is acceptable when in reach of a bath tub, shower, basin or a person in a bath or shower.

Maintaining your fan

Fans must be kept clean and dust-free. Therefore it is a good idea to install the fan somewhere which is easily reached. Fans should be cleaned approximately once a month. Bearings should also be oiled approximately twice a year, but remember to follow manufacturer’s instructions. Before cleaning make sure that all electrical items are isolated!


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