Condensation In Bathroom With No Window - Best Extractor Solution?

[Pgeddon]

Hi all,

We recently had a ground floor bathroom/wet room finished off, It's about 3.6m long by 2.7m wide, tiled from floor to ceiling and has no window in there due to a future extension that will take place on the other side of the rear wall.

Unfortunately, i've Instantly noticed when showering that alot of condensation is forming on the tiles/mirrors and the room stays really wet and humid in there for hours afterwards, which even with the fact we jackoboarded most of the room....its still giving me cause for concern. As I can see wet patches and mould forming on the grout already just a few weeks in.

As part of the bathroom fit, the spark did install a 4" Mentis, Axial type extractor fan in there (pictured). Though doing a bit of research online i'm thinking that this may be the problem as the fan looks quite weak. It has an extraction rate of 73 m3 per hour....and the ducting it's venting through is about 2.5m long...obviously with a right angle bend in it too.... which i've read could well be too long for this fan too?

Anyway long story short, i'm looking at swapping it out for something much more powerful, ideally without having to change the 4" ducting to 6". In-line types not an option as there's no access to the ceiling cavity without making a big hole everytime it hypothetically breaks down.... so i'm guessing from my basic research online that my best bet is to go centrifugal, or mixed type. Either something like the Vent-axia Lo Carbon Quadra/ Vent-axia lo carbon revive, or Airflow Icon60? all seem to have an extraction rate of 220 m3 per hour, so three times as powerful as what i've got now, so hopefully would solve this issue.

Love to get some input on this, am I on the right lines to solving this? are there other things I should be considering too? and has anyone used any of the models above and can comment on their experience? they're all quite expensive so would like to get it right!


pictures below for reference.

 

[ShaunCorbs]

flexi vent slows the airflow down. Longer runs are far better using soil pipes

Yes if not straight eg not supported so duct rises and falls

 

[ShaunCorbs]

Not really on average most are 1.5-2.5m on average

Best is solid and sloped to the grill

 

[Ben-gee]

Can you push a length of 4” soil pipe in from outside, where your current grill is?
Then connect up a centrifugal fan to that, this would not entail pulling any ceiling down and may be enough to solve the problem.

 

[Pgeddon]

Can you push a length of 4” soil pipe in from outside, where your current grill is?
Then connect up a centrifugal fan to that, this would not entail pulling any ceiling down and may be enough to solve the problem.

That is my hope yes. It's an odd layout though this house, it was a bungalow at one point and when extra floors were added they retained the original bungalow ceiling, meaning all the cavities between the ground and first floor.... are not run of the mill haha. I recall it being multi cavitied and all sorts of weird stuff in there.

So I think im gonna try the centrifugal first as phase 1. If not good enough, try change the ducting to solid. If still too wet, then keep the solid ducting and go for an inline one.

Maybe a silly question - but can you run a fan with wider ducting than recommended? I can see how running smaller would cause too much back-pressure. But if I bought a 4'' centrifugal, then one of those 4'' to 6'' converter pieces for the ducting, then ran 6'' ducting..... that would be fine?

Asking because I guess then if I DO swap to an inline in future, a 6'' one would be heaps more powerful.... so seems a better strategy overall.

 

[ShaunCorbs]

Yes will be better as there’s less resistance

 

[gmartine]

bad idea. Those are rubbish imho

I'm sure you're right but you'd think it wasn't beyond man to produce a decent one.

 

[Ben-gee]

I'm sure you're right but you'd think it wasn't beyond man to produce a decent one.

I’ve used the shower light but put a decent mixed flow in-line fan with it and binned the rubbish they come with.
Then it is a pretty good solution (although not for this OP!)

 

[gpbeck]

Here’s what I’d do. Remove a tiled column by the bath, replace with hollow structure connected to low level 150mm waste then out through the wall at low level. Slight drop on the 150mm pipe. Plenty of room at side of bath for a beast in-line fan. Replace column and hide a large grill at the top of the back of it.

 

[gpbeck]

Here’s what I’d do. Remove a tiled column by the bath, replace with hollow structure connected to low level 150mm waste then out through the wall at low level. Slight drop on the 150mm pipe. Plenty of room at side of bath for a beast in-line fan. Replace column and hide a large grill at the top of the back of it.

If shower doesn’t clear you could extract from it just into the main room and let the beast clear it.

 

[Timmy D]

100% get rid of flexi duct. I won’t even use it for a meter run.

 

[Pgeddon]

If shower doesn’t clear you could extract from it just into the main room and let the beast clear it.

How do you mean? extract from the shower to the main room?

 

[Pgeddon]

100% get rid of flexi duct. I won’t even use it for a meter run.

Considering the room has no windows, I am a bit disappointed that the installer didnt call any of this out.... But hey, no point looking back, best focus on the best way to fix it.

I asked Vent-axia whether there'd be an issue running a 4" centrifugal extractor fan onto a 4" to 6" adaptor, then into 6" ducting. They said not ideal, but fine. So gonna go ahead and buy their Lo Carbon Quadra, and swap the flexi crap, for solid 6" ducting. That will be atleast 3x the extraction rate to my current setup.

If that doesnt sort the problem, then i'll go for the vent-axia 150mm inline ACM. and just install a little loft hatch above the bath for future maintenance access to the inline fan. That will be 11x the extraction rate to my current setup. Though hopefully I dont have to go this far.

 

[Ben-gee]

Let us know how it turns out.

 

[Murdoch]

How are you going to change the ducting?

PS I do think you should talk to the installer so they are aware of the issues you are having, so they can learn

If you think it’s bad now, just wait until the winter

 

[Pgeddon]

How are you going to change the ducting?

PS I do think you should talk to the installer so they are aware of the issues you are having, so they can learn

If you think it’s bad now, just wait until the winter

ducting change will be for the sparks that comes and swaps the extractor fan to the centrifugal.

i'm guessing they will core a larger hole from the exterior wall, tie the new ducting to the old ducting, and push/pull it through hoping it doesn't snag on anything. If it does and the ceiling has to come down to get the bigger ducting in, that's fine cause we'd have to cut a hole to get the in-line up there anyway.

But hoping just the fan change will suffice without changing the ducting, as that's the least intrusive option, obviously.

 

[Murdoch]

Flexi vent is 100% rubbish on anything other than runs that are short or need to go around corners

concorde was shaped as it was for airflow reasons

 

[Pgeddon]

Flexi vent is 100% rubbish on anything other than runs that are short or need to go around corners

concorde was shaped as it was for airflow reasons

Sure - but if the problem is fixed, i'll stop there.

if it comes back with a vengance in the colder months as you rightly pointed out - i'd swap the ducting then I guess.

 

[Timmy D]

Sure - but if the problem is fixed, i'll stop there.

if it comes back with a vengance in the colder months as you rightly pointed out - i'd swap the ducting then I guess.

We appreciate your replies/updates 👍🏼

 

[Pgeddon]

Update on this one,

So i've had the crappy extractor fan swapped over to a Vent Axia Lo Carbon Quadra, Centrifigual type extractor fan.

At maximum speed setting (220 m3 per hour), it is preventing moisture in the room, but by god is it loud, its deafening when you're in the room at round 50decibels.

Not something i'm going to be able to get used to unfortunately. So i've tried setting it to half speed (110 m3), noise is then a bearable 37db, and it does keep the moisture off the surfaces for i'd say about 5mins of shower time, but anything longer than that the room does start getting quite cloud, as if it that there's just too much vapour for it to deal with eventually. At which point it does start to form on the tiles/mirrors etc.

That said, I left it running after 10-15mins after the shower stopped and after that time, the room is quite dry again.


If it only stays wet in the room for 10-15.... will that still be an issue with damp / mould eventually, or is that OK?

 

[ShaunCorbs]

That should be ok

 

[Murdoch]

I thought you said the red lines were marking where the vent runs ????????

extractor fan swapped over to a Vent Axia Lo Carbon Quadra, Centrifigual type extractor fan.

At maximum speed setting (220 m3 per hour), it is preventing moisture in the room, but by god is it loud, its deafening when you're in the room at round 50decibels.

You haven't been using it for long enough to draw any conclusions - and remember its a warm dry time of year

20 minutes minimum for the over run timer IMHO

 

[Pgeddon]

You haven't been using it for long enough to draw any conclusions - and remember its a warm dry time of year

20 minutes minimum for the over run timer IMHO

Yeah fair enough, I need to cut a hole now anyway as the spark seems to think the ducting vent on the exterior wall has been cored out too low, meaning the ducting wont be running straight acrosss the ceiling cavity but instead will S bend down for some reason. He advised that needs addressing, so we're gonna cut a nice hole over the bath and see about fitting an Inline ACM125T in there instead.

125T is 30db at max speed of 330 m3 per hour. Just a case of whether we've got enough room in the ceiling cavity, but we need to cut the hole anyway now to see whats going on with this ducting regardless so can't hurt to try and fit one in there at the same time!

 

[Murdoch]

You need to have a steamy shower and see how the fan gets on, then do it again and partly open and see if it clears quicker - if it does then the gap under the door isn’t enough

 

[gpbeck]

Narrow ducting will be noisier, higher velocity and turbulence.

 

[Ben-gee]

Look at Manrose MF125T, 310m3/hr at 25dB

I’ve used the 4” version a few times when there’s a long ducting run as axial are rubbish unless just pushing through a wall.

Again, I use rigid duct where at all possible.

 

[Murdoch]

Fwiw concealing an inline fan above the ceiling needs access

 

[Pgeddon]

Fwiw concealing an inline fan above the ceiling needs access

Yes, i'll update shortly doing the work now - we've added an access hatch for the ACM 125T Vent axia.

Quick question though - when swapping to the solid 5" ducting, we've found a horizontal piece of timber spanning the joists and it wont allow enough space to get the 5" ducting through.

As an alternative - is the flat/rectangle ducting any good? If so what size is equivalent in performance to 5" round? As that may be our only option short of notching out this piece of wood.... but it means ceiling down if so.

 

[ShaunCorbs]

You can cut / notch this timber it’s only there for cross support and tbh 2” is fine

 

[Ben-gee]

204 x 60 is 5” equivalent
220 x 90 is 6” equivalent.

 

[Pgeddon]

204 x 60 is 5” equivalent
220 x 90 is 6” equivalent.

thanks - don't have any where near the width for that. So notching out it is!

cheers

 

[Pgeddon]

Update on this one - Couldn't get the ACM150T in there as there wasn't enough height clearance in the ceiling cavity.

But the ACM125T went in there.... just.... now with 5" solid ducting It's blowing super hard and really not that loud.

No condensation on the walls even during a long shower now, and id say leaving the fan on for about 5 mins post using the bathroom, even the glass shower door was bone dry.

Overkill, perhaps.... but we got there in the end, thanks for all your help.

 

[Pgeddon]

Couple of photos im putting up too before i close the chapter on this one haha.

Forgot to mention when we cut a hole up there and found the old flexible ducting, the installers had nailed an electrical cable to a joist to 'hold' the ducting in place, I presume before the ceiling went up....but the cable was completely throttling it. I guess that explains why the original Axial fan I had did F-all. Certainly wouldn't have helped anyway.

And the other photos, ACM125T neatly in place, solid ducted up and a neat little hatch I made for an access panel should it ever break down in future 😀

thanks again all.

 

[Murdoch]

Not to dampen your enthusiasm for a job well done but until the winter arrives you won't know ho effective the solution is.

Bathrooms need a lot of heat AND ventilation ..................