The Extract Fan, an Essential Bathroom Fitting or Accessory?

While bathroom accessories may seem to be obvious items to be included in general planning they are often overlooked, as the space for them needs to be taken into account at the start of the planning process. Positioning of the bathroom fittings such as the shower, WC, bath and washhand basin all must include placement for the accessories. For example it is it quite an inconvenience and uncomfortable if the towel rail is on the opposite side of the room to the shower. It is unnecessary and should have been planned for in the first place. The following items will make you more aware of detail as a designer.

Every bathroom should have a method of extracting steam and excess moisture. The extract fan is the simplest and most common used worldwide. Not only does it remove the air, but helps circulate the air within the room. Positioning the fan is another job that the designer should do. While it is not a critical decision, it adds to the designer's value. There is a simple principal behind mechanical extraction and ventilation that needs to be taken into account. To extract the air in the room additional air must enter the room so that it is a balanced system.

A vent in the door lets the air in, an extract fan in the ceiling takes the air out creating a balanced system.

A vent in the door lets the air in, an extract fan in the ceiling takes the air out creating a balanced system.

The basic principal relies on positive and negative air pressure. Imagine the bathroom with the fan on and the doors and windows closed. The fan is only a small extraction unit and once it removes a small amount of the air in the room the pressure on the outside is greater than the inside. Hence, negative and positive pressure. Therefore unless air is allowed to enter the room by another source then the positive pressure on the outside will start to push back through the hole where the fan is and although the fan may be spinning it won't be extracting.

So what is the solution?

Obviously we need to get air into the room without making the room so cold and draughty that it is uncomfortable. To ensure that there is a sufficient supply of air for the fan to work one way is to leave the door open however we then lose all privacy so that is unacceptable. The other is leave the windows open slightly but then we are letting in the air from outside and in the winter this is very uncomfortable. A common and successful solution is to discreetly let air in from other parts of the house. This can be from a ventilation system specifically designed for the purpose or a simple solution is to vent through the wall of the bathroom into the hall or an adjacent room.

We can do this one of three ways. A proprietary wall vent set low in the wall opposite that of the extract fan to maximise the distance of the air movement (this will also help dissipate draughts).

The second is to have the vent in the door itself and the third is to have the base of the door shortened by 12 mm or half an inch. This will hardly be noticeable and allows a reasonable amount of air into an average sized bathroom.

Positioning the fan should be as close to the source of the steam as practical and in most cases this will be the shower. As steam rises with the heat it should also be in the ceiling (not the wall) and be vented out side of the building through the soffit or through a cowl on the roof. It should never vent into the roof space in the hope that it will dissipate up there. Try and maximise the distance between the inlet source or vent and the extract system. This will help move all the air in the room not just a certain area. Someone will question about the cold air from the inside of the house chilling the bathroom, however if this is the case and the air inside is colder than that outside the heating of the building or home need to be seriously considered.

Often the extract fan is switched on with the light switch. This is not recommended as it reduces the versatility of the control of the room.

So is the extract fan an essential fitting or an accessory? Definately an essential fitting!