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Acceptable Noise Levels of the Domestic Extractor Fan

Acceptable Noise Levels of the Domestic Extractor Fan

If you’re in the process of choosing and researching a domestic extractor fan you will know that there are many technical aspects to consider: room size, number of air changes per hour, extraction rate, part L of the Building Regulations, the bathroom zoning system, duct length and resultant air pressure, IP rating, energy usage… the list seems to be endless!

The decision to retrofit an extractor fan is usually motivated by the need to expel steam from a bathroom or cooking smells from a kitchen and is made by the property owner. When installing a fan in a new build a property company or electrical contractor will install fans in order to meet Part L of the building regulations. In both cases the single most important factor is the air extraction rate – how much air is removed over a given period. This is stated in metres cubed per hour (m3/hr) or litres per second (L/s).

However, an important consideration which is often overlooked by the homeowner and somewhat understandably ignored by the third party contractor is the noise generated by the fan when in operation.

Most manufacturers state the noise level of their extractor fans in decibels dB(A) within the technical specification. Such information is now easily found on the websites of manufacturers, retailers and wholesalers. Those fans which do not clearly show the dB(A) probably have something to hide and should be avoided.

So what is an acceptable level of noise? To some degree this is subjective; what is fine to some may be annoying to others. The installation and fan type, however does have a large influence on this answer. Most kitchen fans are six inch, which is to say they use a six inch impeller. (As opposed to most bathroom fans which use a four inch impeller). Consequently a larger motor is required to drive it. There is simply no way of avoiding the fact that a larger motor will result in high decibel level. Indeed, even the quietest six inch fans are louder when in operation than the noisier four inch ones. However, the kitchen is a room which can accommodate higher decibel levels. Why?..well think of how the fan is being used: Almost certainly the fan is being used to extract cooking smells. In this situation the user and other dwellers in the property will be far less aware of the noise of the fan, being obscured by the sounds of food preparation.

Four inch fans however are used at entirely different times. Night time visits to the bathroom or toilet, for example, when the house is entirely quiet are much more audible. The opening and shutting of a door, the creak of a floorboard all can be heard in different parts of the house. In this situation fan noise is much more prominent. Until recently this simply could not be avoided – Motors were inherently noisy. However almost all manufacturers now make a specifically quiet fan or range of silent fans. Whilst most normal four inch models operate at around 30 – 40 dB(A), these quiet or silent models operate at around 24d(B)A. Providing the fan is installed properly, and is not mounted on a wooden joist, they will be silent, even in the middle of the night.

More information on quiet extractor fans is available at Extractor Fan World.

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