Bathroom extractor fan location

hatt55

I'd previously received some advice on here about insulating/replacing a bathroom ceiling. Unfortunately I think that money needs to be directed elsewhere, so the plan now is just to install an extractor fan to get some improved ventilation. The question is where!

The bathroom is at the back of a Victorian terrace. Its a pitched roof. A you walk in, the shower cubical is immediately ahead making use of the higher part of the ceiling with the elevation dropping to the right. It backs on to a disused chimney breast, so the wall is sort of double thickness. To the right of the shower (and chimney) is the window.

A roofer suggested that it would be very straightforward to put the extractor immediately above the shower cubicle as they could just install a vent tile in the roof above and this would connect directly to the extractor and there would be no need for lots of ducting. This seems sensible and I am very happy with the idea of something straightforward! However, I've done a bit of reading and some people suggest that this kind of set up can result in condensation dripping back down and potentially causing issues with the fan/causing that part of the roof to get damp if it isn't installed properly. 

So I'm wondering what my alternatives are. I can't see how you could set something up directly above the shower where the condensation could run out. This feels true of any extractor that is in the ceiling of a room. Alternatively I thought that one could go in the wall next to the window - there is a little gap between here and the start of the chimney. But then you'd still have all the steam rising from the shower and having to make its way to the extractor. 

The rafters run from left to right but there are no eaves that a vent could be installed in. 

Any suggestions?

FlorayG

So have it installed properly. My house and both my rentals have the extractor vent above the shower and I've never had any problems

hatt55

I mean, if having problems with this arrangement is the exception rather than the rule then I'd be very happy to do it (and hope that the electrician is competent).

WIAWSNB

Hi.

Could we have a pic, please? It's hard to suggest where a vent could be ducted through, if we cannot see it.

But, there is certainly nothing wrong with having it ducted through the roof, other than I wouldn't like my roof covering touched unless absolutely necessary!

Having a short duct length is good. Yes, there is a risk of condensation dripping back down any vertical pipe, but there are ways to mitigate against this - eg insulation, keeping the fan going on an over-run timer until the duct is absolutely dry, having a fitting that will collect any such formed condie, etc.

An inline fan should be ok against any cond running down inside the duct. You may get a drip coming out the ceiling grille, but I doubt it - and you'd just fire up the fan for longer.

Ducting through a wall is usually easier and less disruptive, but I cannot tell if it's suitable in your situation.

sheenas

Bathroom are deviced into safety zones. Bathroom zones are defined areas within a bathroom, dictated by the proximity to water sources, to ensure electrical safety. These zones determine the type of extractor fans and other electrical appliances that can be installed safely. Specifically, Zone 0 is the area inside the bath or shower tray, Zone 1 is the area vertically above the bath or shower to a height of 2.25 meters, and Zone 2 extends 0.6 meters horizontally from Zone 1 and up to 2.25 meters vertically. 

So you would need a zone 1 cyclone fan. The building regulations require bathrooms without openable windows to have an extractor fan with a minimum extraction rate of 15 litres per second. The fan i used when upgrading my bathrooms was able to shift 4 x the volume of air within the bathroom and work extremely well, but was £80, so quite expensive.

casper_gutman

We have the extractor directly above our shower, venting through the roof. The actual extractor is mounted on a rafter in the loft space above the bathroom though, so there's no issue with zones. The only thing above the shower is an inlet to the duct.

As a through-roof extractor can't slope down to the outside as an eaves or wall vent could, I think the correct approach is to achieve a constant upward slope, and position a condensate trap to intercept water condensing inside the duct. I must admit we don't have this, and the installer used flexible ducting. It is a short run though, and insulated ducting. Anyway, we seem to have got away with it so far having had no issues for eight years and counting!

hatt55

Thanks for the comments. Perhaps it isn't so difficult after all - a classic case of me overthinking things rather than just getting a professional to do a thing.

Here are a couple of pictures, one showing the area above the shower. You can see that the ceiling is a bit steam damaged/discoloured. The textured coating was tested negative for asbestos a while back. You can see the wall comes in a bit where the chimney is and then the whiteish tiling is some boxing where I assume all the plumbing/shower electrics sit. Also a picture of the roof. Rendering of the chimney stack is on the list....its a never ending list! The ceiling in the bathroom flattens out whereas the roof is a constant gradient, so there must be a bit of void space above. 

Things to ask a tradesperson then: will they install a condensate trap, insulation around the duct, Zone 1 fan.

grumpy_codger

I'd make it through the wall above the window.

hatt55

grumpy_codger said:

I'd make it through the wall above the window.

If something above the shower wasn't a goer then this seems like the alternative. What makes me lean towards the shower option is that it seems as though it might protect the ceiling directly above the shower a bit more i.e. to get to an extractor above the window, the damp air still needs to go past the bits of the ceiling/walls that are already steam damaged. That might be a simplistic view of thing though. 

WIAWSNB

IF they provide a decent quote for having it extract above the shower and venting through the roof, then great; I'd agree it's the best extracting setup - get rid of the steam at the point of manufacture.

If.

Otherwise, also get quotes for thro'-the-wall venting as Grumpy suggests. It shouldn't be too far behind in the effectiveness stakes, and could be a lot cheaper.

For either, choose the actual extractor carefully. Some have very useful features such as background venting, humidity, timing, and even 'odour' detection, are super-silent, and even App-controlled. Yup, you can sit on the pan, and dial up what is 'required'...