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Do Extractor Fans Waste Energy

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Do Extractor Fans Waste Energy

By Ruth MacEachern

Product Manager

Nov 15, 2023

As the weather cools during the winter and you start to use the heating more in your home, you may be worried about the impact of using an extractor fan in your bathroom or kitchen.  Heating costs are high at the moment, and wasting energy by allowing warm air to be removed from your home could mean that your bills might rise. 

Why are extractor fans important

Most homes have extractor fans installed in their bathrooms, kitchens, and other wet rooms such as the WC and utility room.  These fans help to expel humid air from bathing, cooking, as well as from washing and drying clothes.  If the humid air is not removed, it can build up in your property causing condensation.  Over time, if condensation soaks into surfaces such as walls or ceilings, it will lead to damp patches where mould can grow.  Damp can damage the fabric of your home while toxins and spores from mould can seriously affect your health.

Ensuring that you have well maintained extractor fans in rooms that are a source of moisture prevents condensation and improves the air quality in your house.

Do extractor fans cause heat loss

As an extractor fan runs in your kitchen or bathroom, it draws the moist air from the room outside and allows it to be replaced by air from elsewhere in the property.  Building regulations set out guidance about the minimum amount of airflow that is required for intermittent ventilation in different rooms of a property.  For a kitchen with a hood over the stove, the extractor fan should extract a minimum of 30 litres of air per second, while in a bathroom, the amount of air removed should be a minimum of 15 litres per second.

During a bath or shower, the total amount of air removed from the room by an extractor fan might seem quite high – over 600 seconds the fan should remove some 9000 litres of air, however this amount is not as big as it seems.  9000 litres of air would represent a cube about 1.7m in dimension, or about 1/3 of the total air in a bathroom measuring 3m by 3m.

In terms of the cost to warm replacement air by 10oC, the heat lost in the extracted air over a 10-minute period, is about £0.03 at current prices.

Minimising heat loss through extractor fans

There are several ways that you can reduce the amount of heat lost via an extractor fan.  The first is to ensure that you leave the bathroom or kitchen door closed during and after bathing or cooking.  Aside from stopping humid air escaping into the rest of your home where it could cause condensation, this also stops warm air from elsewhere being drawn into the room and lost.

It is also possible to install single room extractor fans that have an integrated heat exchanger that captures the warmth from the air and uses it to heat incoming air.  The HeatSava from EnviroVent is a highly efficient model that can recover almost 85% of heat lost during extraction.

Find out more

While some heat can be lost from your home when using an extractor fan in a bathroom or kitchen, the amount is small relative to the overall size of your property, and the effects of not using extractor fans – condensation, mould, and damp – are much more damaging and expensive to resolve.  Choosing a more efficient extractor fan could help you.  For a free home survey from your local ventilation specialist, please enter your postcode below.  They will visit your house and identify the causes of condensation and provide advice about the best solution for your needs.

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One of our local experts will contact you to learn more about your problems, offer free expert advice and make recommendations for a permanent solution.

During the free survey we will

  • check Assess any condensation, damp or mould problems in your property
  • check Take readings of the relative humidity levels
  • check Identify any underlying problems and make recommendations for a permanent solution

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