Bathroom Extractor Fan

[viz48]

I am about to replace an extractor fan in my shower room. Tiler who is regrouting my shower says the build up of mould is party due to the fan not being strong enough. what sort of spec should I look out for ? ie cubic metres per hour etc. Would also like one that doesnt sound like a train running through the house!! . It would be on a separate switch from the light as that is the present arrangement which I quite like. Would also like one that doesnt blow down draft when not in use ( some sort of cover?). Thanks for any suggestions and advice......V

[Count-A-Strong]

You can get them with a motorised vent cover. A 4 inch diameter one should be fine for a shower. The noise will be coming from the material its fixed into more than the fan itself.

[Clanad]

Your on the right track already... measure your bathroom to determine the cubic foot (meter) volume. all bathroom vent fans (as they're called here in the U.S.) are rated for cubic foot per minute volumes. Most are also rated for decibel of sound. The actual roof vent should already have a "flapper" valve that opens and closes in reference to the air pressure produced by the fan. Most higher quality fans also have such a valve at the very end of the exhaust structure on the fan. It'll have a rubberized gaske that seal pretty well when the fan is off.
If the fan is exhasuting through the roof above the bathroom (as opposed to a side wall) and if your winter temperatures consistently get below freezing for any length of time, be sure to form a gooseneck in the exhaust tubing before it exits the roof to trap condensation and keep the valves from freezing. It won't be that much water and will quickly evaporate once the weather has warmed, but if it is allowed to flow back into the fan, it'll eventually stain the ceiling around the fan trim fitting. I speak from experience, unfortunately...

[The Builder]

There are plenty to chose from .............. have a look at this lot to begin with:

http://www.screwfix.c...ooling/Extractor-Fans

As Count Arthur says, 100mm is usually used .......... 85-100 cubic metres per hour approx.
If you're after an even better suck .............. then I've fitted 150mm kitchen fans before. Check the dBA (noise rating) ............ there are some especially quiet ones available.
Lots of good stuff from Clanad to think about too......... regarding ducting and terminals.

[viz48]

Thanks gents

[Dodger666]

Get one with a timer fitted so it will continue to run on for whatever period you set after you have switched it off and left the bathroom. If you switch it off immediately there could still be moist air in the room.