Re: choosing and siting bathroom extractor fan

[chris French]

In message , nick writes

Hi >I'm hoping somebody might be able to give me some advice on picking >and siting a suitable bathroom extractor fan. >(It seems to be a subject that few people know much about) > > >1) I was planning to put a ceiling extractor fan >in the corner above the shower. > >Would it be better to site the extractor >2) on the outside wall in the SIDE (NOT ceiling) >3) in the CEILING but in the outside wall corner above bath > >My overriding consideration is to extract as much >condensation as possible, most of which will come from >the shower, but also the bath which gets used more rarely. >

I don't think it matters, I have fan (standard 4 inch in line fan) mounted in the ceiling space, venting through the roof via about 3-4 metres of pipe. The fan vent is mounted in the middle of the room pretty much, it does the job stopping condensation fine. We've had no problems with damp, mould etc. in the shower

Bathroom fans don't suck lots of air, so the steam from a shower will get all round the room anyway, even if the fan is right above it.

>PICKING RIGHT PUMP

Our bathroom is a bit smaller, (about 15 m^3 I reckon) and as I said the standard 4 inch fan in dusting works fine. I think ours is a Manrose. I would think it averagely noisy - less so than say wall mounted fans - I would say it is noticeable but not intrusive to me. I think it did come within whatever the recommendations are for venting bathrooms in terms of air changes per hour, but anyway it works.

Too keep noise down I think probably a bigger fan moving slower is probably better - small fans running fast will be nosier, but I don't know how much bigger you would need to go to get a benefit.

I fitted a humidistat to ours (which can also be switched manually). It works pretty well most of the time, normally turning the fan on a couple of minutes after turning on the shower. It does turn on occasionally due to general atmospheric humidity, normally very rainy. For 95~% of the time it comes on as expected, once I tweaked it carefully.

[BillR]

I'd go for the wall mounted option In my opinion the ceiling fans with ducting, unless they are the centrifugal type, are not very good. They will work but take a long time to extract. The other problem is, if they are mounted on a plasterboard ceiling, the vibration can be quite noisy.

Another important consideration is that the fan must be appropriate for the zone of the bathroom it is in. What you can put in each zone is regulated In the shower area ( and probably above the bath) is the most rigourous zone. For these areas you would need a proper low voltage model which aren't cheap

[ARWadsworth]

And if your bathroom door fits snug you will have nothing to replace the extracted air with.

Adam

[Andrew Gabriel]

Reminds me of a small room in the middle of a new school building which contained just a WC, no windows, but an extractor fan connected to the light. After a few days of use, the extractor fan 'sucked' a sheet of plasterboard off the wall. The room was rather too well sealed, and although the fan might not seem very powerful, even a tiny pressure difference across an 8'x4' sheet of plasterboard adds up to quite a force (and I doubt it was fixed very well in the first place).

[nick]

Thanks very much for everybody's advice.

I will definitely go for a fan sited above the shower, in the loft and inline in the ducting. This I hope will be the quietest option.

BUT I'm still not sure what the minimum extraction rate in metres cubed per hour for my bathroom should be though. I'm tempted to go for the 93 metre cubed / hour fan Richard mentioned from cpc.co.uk (good site) but am concerned it wont be powerfull enough.

I read up that a bathroom fan should replace the rooms air 15 to 20 times per hour. Therefore with a room volume of 21m3 (2.7 metres high by the way) 15 * 21 = 315m3 per hour extraction rate. This is way higher than all the fans Ive looked at (which are mostly 80 - 90m3) Also bearing in mind the extraction rate drops like a stone the more ducting you use and I plan to run it 3 metres. Also I have a feeling that a fan with a extraction rate of

300m3 / hour might be a bit on the noisy side.

Another big pain is a lot of the pumps dont have a decibel noise level rating so how the heck do you know how loud the thing is going to be unless you fit the dammed thing in.

I am going to speak to a bathroom installer expert tomorrow who I have heard sells a REALLY good fan (but for £139). I want to know why its so expensive and why he thinks its worth the extra money.

Hopefully I will decide after that

Thanks again Nick