Ventilation Ducting for Kitchens and Bathrooms

Summary: Information and advice on ventilation for bathrooms and kitchens using extractor fans and ducting to mechanically remove moisture and odours. Get ideas about how to ventilate the rooms in your home that could be prone to damp.

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Bathrooms and kitchens produce the most odours in the house so they need the most efficient type of ventilation. However it is not just the smells that require attention, it is also important to remove as much water vapour as possible to reduce condensation. Kitchen and bathroom ventilation is now an important green issue.

Condensation occurs when warm air comes in contact with cold surfaces and this is most likely to happen in bathrooms. The life style of washing and cooking for a couple living in a standard sized house will produce about four litres of moist air per day. In previous years, natural draughts would have taken care of this amount but in the drive to retain heat in the house – cavity insulation and double glazing – this moist air can be trapped.

It is possible to fit a ‘whole house’ ventilation system but, provided the kitchen and bathroom have an external wall, it is cheaper and more efficient to treat them separately (although if the two rooms are adjacent it may be possible to connect them with ducting at ceiling level). Bathroom fans are fixed to an external wall (or occasionally to a window pane) and the rate that they discharge the used air is measured in litres per second (Ls) or cubic feet per minute (cfm).

The capacity of the fan should be stated on a label. A rating of 25 Ls is considered adequate for most sized bathrooms but advice should be sought for larger or irregular shaped rooms.

Fans can include a ‘run on’ facility where the fan is linked to the room’s lighting and will continue to perform after the light is switched off. Some fans have the time delay built into the fan’s controls by the manufacturer but it is possible to buy fans where the householder can set the time that best suits the family’s needs.

The two main concerns householders have about the insulation of fans are the noise and appearance. Some fans will have ‘low’ or quiet’ on the label but because none will be marked ‘noisy’, it is probably better to seek advice on the likely performance! Fans should be cleaned on a regular basis because they create static electricity which attracts dirt and this can turn to mould if neglected and cause health problems.

There is a wide range of kitchen extraction systems available and the best ones are the combined fan, hood and duct packages. Bathroom fans range from £50 to £200 whilst combined kitchen systems cost between £400 and £1200. The cost of fixing these appliances is say £150 to £250 and these should be added to the above figures.


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