extractor fan

[jackfoley]

Hi,

I was wondering how one can tell if an extractor fan model is sufficient.

I have wired the existing one and it seems to take the steam out of the bathroom pretty quick but the mirrors and tiles still get steamed up.

Do i need to install a higher capacity fan or is steam on the mirror unavoidable?

The existing fan is a cheap one.

 

[stem]

To see if your fan is big enough, calculate the volume of the bathroom in cubic metres by multiplying the room's height by its width by its length. Then multiply this by the number of required air changes per hour (This varies depending upon who you ask, but around 10 changes per hour seems fairly average for a bathroom, although some recommend as much as 20) to get a volume of air per hour. Does the fan you have equal or exceed this value? If not your fan is too small.

Even a bigger fan will not prevent condensation forming completely. As soon as moist air touches a cold surface it will condense. The only way to stop it completely is to keep the temperature of the surfaces above the dew point, which in most cases is totally impractical. However, proper ventilation will get rid of the moist air quickly once the source has gone, and the drier air will the help get rid of the condensation that has formed.

If you fit a fan that is larger than you need, you will also extract more heat from your home.

 

[mointainwalker]

If you thought it worthwhile you could fit/get fitted a heated mirror which wouldn't mist up, but that does nothing for the tiles. Is that a real problem though ?

 

[JohnD]

the temperature of the tiles and mirrors will make a difference, so will the position of the fan and how long you run it. I have a basic axial fan, almost directly above the bath, and the mirror is on the other side of the room and does not get misted. However the bathroom rad is close to the mirror, so that side is fairly warm (especially as it heats up whenever the cylinder is being heated) and the mirror is spaced off the wall on pivots, and the wall is cavity insulated so not very cold. I also put the fan on the wall opposite the door, which has a gap under it for warm fresh air entry from the rest of the house.

Because my bathroom fan comes on with the light switch, it is always running before,during and after every bath or shower, so the moisture does not have much chance to accumulate. Some people have a psychological aversion to ventilation and will not turn fans on.

I am quite careful about condensation, so maybe I have arranged everything to best effect, can you see any points you could look at?

You might consider a long low radiator to keep the wall warm, and replumbing it so that it operates when the boiler is heating the cylinder (this will not apply if you have a combi) so it is always hot during and after a bath or shower.

If you need a more powerful fan, the Centrifugal ones are generally quieter and more powerful than the axial ones.