bathroom extractor fan

[con1_uk]

Hello,

Our bath room extractor isn't quite working properly, our celing is getting black mould on it, I have worked out it does seem to operate better with the windows closed. I have held a piece of toilet paper up to it and it keeps it there.

Upon inspection in the loft it is a small unit that fits inbetween the extraction pipe, are these standard? Are they easy to fit?

Any advice on the mouldy celing please. This room just has a shower.

Thanks.

 

[ericmark]

My house sits at 44% humidity at this moment and outside it is sitting at 81% humidity if we calculate the due point however house is at 10°C and outside at 2.9°C so if the bathroom air is replaced from outside then there will be far less moisture in it.

However bringing in air from outside will mean a cold bathroom which clearly is not wanted. So to get drier air without cooling the bathroom down you need a heat exchanger so hot air going out heats the cold air coming in.

There are two types of heat recovery units those with two fans one pumping air in and one pumping air out and those with a single fan which pushes the air out and relies on the depression in the room drawing in the replacement air. With the latter the doors need to be a good fit.

However without a heat exchanger then doors need to have vents in them to be able to draw in the warm air from the house. Also of course that air must come from some where so no open flues allowed or smoke may go wrong way and need vents in the house for air to get into the house. You can also read this as living in a draughty house.

Use a vented tumble drier, and vented cooker hob and a bathroom fan and the total amount of air your pumping out will mean more drafts than in the days of open fires fitting front and back doors with really good seals and as is common filling in air bricks with expanding foam is the main cause of mould in the bathroom.

Opening a window after a shower and closing it half hour latter will help but if anything like me you forget to close it.

Oddly the problem is not so bad in the Winter my house in Winter sits at between 36 - 45% humidity in summer 50 - 60% humidity simply as cold air does not hold as much moisture. Living in Hong Kong it was a real problem the AC had a constant run of water from it as it removed moisture from the air it was impossible to stop mould growth it was a weekly job to wash wall of shower room with bleach.

Bigger fans will not really help you have to either take in cold air from outside and use the central heating to warm it or use a heat recovery unit.

 

[sparkwright]

Hello,

Our bath room extractor isn't quite working properly, our celing is getting black mould on it, I have worked out it does seem to operate better with the windows closed. I have held a piece of toilet paper up to it and it keeps it there.

Upon inspection in the loft it is a small unit that fits inbetween the extraction pipe, are these standard? Are they easy to fit?

Any advice on the mouldy celing please. This room just has a shower.

Thanks.

Sounds like the unit within the extraction pipe is the fan itself, known as an inline fan. So that would make the vent in the bathroom just a simple grille plate.

You need to confirm this before we go much further.

Inline fans are easy to replace - just make sure you fit the unit the right way round, or you'll have air blown into the bathroom!

You need to confirm if you have a timer fan or not. A timer one is typically operated when the light is turned on, and runs for a few minutes after the light is turned off.

 

[JohnD]

you can very probably get a more powerful and quieter inline fan that the one that was fitted. Post a photo, please, or at least a description, of your old one.


Yes, extractor fans do work better with the doors and windows closed. It will actually suck in replacement ait through the gap under the bathroom door*. This will not be especially cold, but it will lie at the bottom of the room while the hot moist air rises towards the ceiling where the fan will suck it out, which makes extractors more effective than open doors or windows.

*Unless you have airtight doors which is very unlikely.

 

[con1_uk]

Hello, yes it sounds like an inline fan that we have, the grill in the bathroom has no moving parts at all. I will try and get a picture from the loft. So are more powerful ones available and will they help?

 

[JohnD]

yes and yes.

rubbish example
http://www.screwfix.com/p/manrose-in-line-shower-fan-kit-chrome-100mm/71740

good example
http://www.screwfix.com/p/vent-axia-acm100t-w-in-line-bathroom-extractor-fan/53730

look at the extract rates.

We may have suggestions about the duct as well, when we see it.

 

[con1_uk]

The cheaper one looks ok lol, how do you find out the extraction required? My room is only 3ft by 10ft.
One handy feature on this unit would be the timer, the current unit goes off as soon as you turn the light off so a timer of 30 mins would help

 

[RF Lighting]

Punch your details into here and it'll tell you how powerful your fan needs to be. Then just make sure the replacement fan is at least as powerful, but the bigger the better really.

http://www.tlc-direct.co.uk/Technical/Ventilation/Ventilation4.html


Enabling a timer over-run may be straight forward or may require some rewiring of the circuit depending how it's currently wired.

 

[con1_uk]

Thanks for the link, very helpful.

I was thinking the same about the overrun, the current one goes off with the lighrs...
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