Damp in bathroom - better fan or dehumidifier?

[MyNameIsInigoMontoya]

We have a big moisture issue with our bathroom at the moment - it is starting to get mould not just on the ceiling but also coming down the walls round the window, and I'm wondering what's the best way to deal with it.

Current situation is we have a wall extractor fan, relatively new, says on the box 100mm and 21 l/s (Xpelair one, with humidistat and timer) but it doesn't seem to help enough. It doesn't seem to extract enough, and seems to stop before it's fully dry. Unfortunately as we're usually rushing out in the mornings I don't get to open the window enough either, and this time of year the heating doesn't come on much (fairly well insulated house) so the damp is just hanging around.

I'm thinking we either need to upgrade the fan again (DH will moan about this though, but I did question whether this one had enough power when we got it...) or consider a dehumidifier - but I'm not sure about that as there's no really good place to put it, so it would be standing around in the middle of the floor and getting in the way. (Also seems to cost more!).

Would you agree that beefing up the fan further is the first thing to try? Or any other suggestions? Thank you!

Install an electric heated towel rail so you can keep it on when the central heating is off.

Do you have the kind of window that can be closed with a gap to ventilate? Or has separate vents? If not you could consider replacing it.

You also need to scrub off all the mould (vinegar stinks but is effective) and you could paint the ceiling with anti-mould bathroom paint.

I can't comment on the fan as I don't know how it compares to other on the market - it might be worth replacing if there is another option which is significantly more powerful. Also sorry if it's obvious but are the settings correct i.e. set up to run constantly / every time light or shower goes on / as soon as humidity reaches a very low minimum?

PS I agree with you that a dehumidifier isn't ideal because it's bulky and gets in the way - we have the same issue in our bathroom.

We had a damp bathroom, 1920s house, never dried out after a shower in winter due to cold walls, then we got a small dehumidifier and it is like magic. We just leave it in there running after a shower and it warms the room slightly and takes all the water off the surfaces.
Come morning there's never much in it, I think it only really runs for a couple of hours before it clicks off.
The electricity cost is minimal as we are only doing the one room.
Does take up a bit of space but it doesn't bother us much. Better than mould.
I think the unit was about 160 pounds a couple of years ago.

Definitely a dehumidifier - much better than extractor we have found. Meaco is the brand recommended by WHICH. Love ours!!

Get a ducted in line fan that sits in the ceiling and sucks the moisture up and out. They're not that expensive and an electrician can install it for you. Ours has made a massive difference. It runs for 30 minutes after you switch it off. We originally had a fan in a window that did absolutely nothing. Our new fan is very quiet and the cabinet mirror doesn't even get steamed up now!

We had the same issue and our dehumidifier is amazing. It takes in about 2 litres a day form our house!

Do you have the window open when you bath / shower? That would help to.

Hm, quite mixed replies! But thanks for all the suggestions. I'll have to have a think and also see what I can get DH to agree to. He's reluctant to do anything involving much work/disruption as he already put in the last fan and gets a bit huffy if I suggest it's not up to the job! So a ceiling fan is probably out...

Re the window, it is quite a big window and no ventilation gap, so it's all or nothing and a bit too cold with it open. Also the paint is already anti-mould paint but it doesn't seem to help when it gets sopping wet!

I'll have a bit more look into dehumidifiers... maybe there's a small/cordless one we can tuck under the chair or something...

Cannot comment whether fan is powerfull enough. If it has a timer then it could be adjusted to run on for longer. If you dont have any heating in bathroom then after shower leave door ajar when fan is running to allow warmth from house to be drawn into bathroom. Leaving window open just pulls in cold damp sir from outsidd especially in winter which wont help. Walls need to be bleached to kill of mould..My main concern would be using any type of plug in appliance like a dehumidifier in a bathroom is extremely dangerous

We’ve got a humidity controlled fan and it still isn’t enough. DH thinks it is because the fan is just above the window, so it’s just sucking air round in a circle rather than taking the damp air from the rest of the room. I think a dehumidifier is our next step.

Luckily we have a plug on landing just outside bathroom!

show us a pic of your fan please in its position.

21 litres per min is about 76 cu.m per hour, which is right at the bottom with cheap builders fans. You can get extractors of about three times the power, but they are larger so I'd like to see how yours is fitted. Do you have access above the ceiling, for example in the loft? Better fans are actually quieter, as well as more powerful. They run for about 100 hours on 14p of electricity.

if it is next to the window you have to shut the window so it can create some suction in the room which will prevent steam drifting round your house. It will draw in sufficient air through the gap under the door. Extractors are more effective when door and window are closed.

You could improve things by setting it to run for longer periods. It might be possible to adjust the sensor, or if you understand these things, set it to run continuously. I use a fan that comes on whenever the bathroom light is turned on, and get no condensation, but it will depend on your house construction and frequency of steamy showers. Don't pay someone to adjust it, you'd do better to change it for the same amount of work.

IMO humidity sensors are not very good because they will not start running until the room is already damp, and they will turn off before it is fully dry. Additionally, they do not keep the bathroom fresh during non-bathing activities.

Here's a pic. Will answer the other Qs in a sec...

UniBond Aero 360° E-connect Moisture Absorber / Device + 1 x 450g neutral refill tab https://www.amazon.co.uk/dp/B01LCHCU0M/ref=cmswwrcppapi_t585zb4JF076D

We use one of these which does the trick.

Right, to answer the other points/questions:

• We do have a radiator in the bathroom, it's just not been coming on much lately as the house was reasonably warm (thermostat controlled from downstairs). So it's not really been cold, but we've missed the drying effect.

• I've already played with the fan settings, so it should now be at max runtime once it starts, and pretty low humidity trigger.

• We went for a humidity-controlled one because we don't always have the light on when showering (the blind lets in enough light during the day) so a lightswitch one wouldn't always get activated, and I didn't think we'd always remember to switch it on manually. (I suppose PIR might work though, but hadn't heard of PIR extractors till today!).

• Door and window are always shut when showering. Too cold otherwise!

• We do have access to the ceiling via loft, though it would be hard to convince DH we need to start chopping holes in the ceiling. (He is still insisting we just need to clean and repaint. I have pointed out I'm not repainting the whole room every few months and also, that won't sort out other issues like the mould round the window seals. Even my basket for toilet rolls went mouldy!).

• If we do go for a dehumidifier, realistically it would have to be a cordless one. So no safety concerns.

Thanks again for all the help!

thanks for the pic.

the fan is not ideally positioned. Water vapour is lighter than air (hence clouds) so it tends to rise towards the ceiling and stratify. Cooler, dryer air tends to lie beneath it.

I suppose you have a 4"/105mm hole in the wall, and I have a feeling it is an older house with solid walls (no cavity). You might reduce the condensation on the ceiling by adding more insulation, but if the eaves overhang that wall, there has to be enough of a gap for ventilation of the loft. Maybe have a look to see if the insulation covers the ceiling and is cut neatly right to the edge. Depending on roof slope it can overhang the wall partially as long as you can see daylight through the gap.

You may not yet be ready to upgrade the extractor, but when you are, a ducted inline fan like this can have two or three times the power of your current fan, and be quieter. It is mounted in the loft and sucks through a grille in the ceiling, and exhausts through a duct poked through the eaves, or a hole in a gable wall.

The one I link is a good brand. Cheaper ones are available. Performance is 160m3/hr, noise at 3m = 24dB(A)

This one is 250cu.m/hr

The "T" ones with timers can be adjusted up to 30 minutes.

Being in the loft, the sound is further muffled.

Several people on here have fitted extractors similar to these.

We live in a rainy part of the country so dehumidifier works best for us as actually dries air in room. The fan (we have one also) leads to more fairly saturated air being drawn in.

it will depend on the temperature.

If indoors is warmer than out, the outdoor air will become dry when it is warmed.

Sorry, busy day so not had a chance to get back!

Thanks for the recos PigletJohn, I'll have a look at them and see if I think I can persuade DH. As you said they are quiet that might help to persuade him, cos he doesn't like the noise from the current one if it runs at night (although that was supposed to be a relatively quiet one).

I'll have a look in the loft again too when I get a chance (though I'm about to be away for a few days so probably not soon). I think it is pretty well insulated right to the edge, and it usually seems pretty dry up there, but will check.

As far as I know, we do have a cavity wall there, but will check with DH (he must know, from fitting the old fan). The worst condensation seems to come on the window and the external wall, I think that is usually worse than the ceiling.

Hi, Ive a very similar problem and wondering how this problem was solved. We have bought a flat with an internal bathroom, no window and no access to external wall. An electrician suggested that a dehumidifier could be put in the adjoining cupboard with a fan in the bathroom drawing the moisture through to the dehumidifier. A manufacturer didn't like this idea, said it would lead to a microclimate and could make the dehumidifier unsafe. I was also told never to put an electric dehumidifier in the bathroom, even though some are marketed as being suitable for the bathroom. The flat is being rented out to 3 students so I cant exactly expect them to wheel in and wheel out a portable dehumidifier. (Which I cant use in the bathroom for safety reasons due to it being electric anyway). At a loss & would be grateful for suggestions.

Can you have the time the fans runs extended? Does it come on with when the light is switched on? Could it be changed for a more powerful one? Is it properly vented to outside?

Dehumidifier is indeed a good idea to reduce the amount of steam in a closed space. I don't agree to the other answer which claim that the dehumidifier will make the room warm, But infact it does just the opposite.

Steam means heat, if we remove heat further from it, it will turn to water, & thats the working principle of dehumidifier..!

a dehumidifier moves heat from one part of itself to another. So water condenses on the cold part and can be drained away, and the other part warms up and heats the room. Fridges do the same.

Since the machine is not 100% efficient, all the wasted energy goes into warming the room.

Larger split air conditioning plant has the "hot" side outside the house so the heat can escape, or sometimes it pipes hot air outside with a big hose. Domestic dehumidifiers don't usually remove the heat from the room.

Backing up everything Piglet says. The fan you have is in the wrong place, too low capacity and not running long enough.

Many guides say 10 air changes per hour for bathrooms. But look at a detailed guide and you find recommendations for 20 air changes per hour for showers. Showers add dispersed fine droplets of water not just water vapour.

A modest 2m x 3m bathroom has a volume of around 15 cubic metres so a fan shifting around 300 cubic metres per hour in Piglet's second link is the smallest fan I would recommend. I would actually go higher and live with the extra noise. Most of the noise is generated by the air flow though the intake grill anyway, not the fan itself.

If possible use 100mm plastic soil pipe not the flexible ducting as that will greatly reduce noise, and improve flow slightly.

Put the inlet directly above the bath and/shower.

I do not support humidity switched fans for the same reasons as Piglet.

I would just wire it into the light circuit in the normal way and train users to switch on as they enter - and before starting the shower. Set the run on period to whatever the maximum the fan will support.

Make sure there is an adequate gap under the bathroom door to allow fresh air into the bathroom as the fan is drawing the stale wet air out.

'What goes in must come out, unless it stays there' my old tutor used to tell me.

As Piglet says, dehumidifier is just treating the symptoms not solving the problem.

@Pigletjohn

Have damp issues in ensuite that can no longer be ignored. About to order a dehumidifier and also purchase the TLC inline extractor fan 250 that you linked to. Would you advice to do both or will the fan be enough?

Dehumidifier link

m.clasohlson.com/uk/Cotech-20-l-Dehumidifier/Pr182799000