Steamy bathroom help

FlaatusGoat

Small family bathroom here, no windows. Showering creates a lot of steam, so much so that the walls sweat. Thankfully when I renovated it I used bathroom paint, and it's held up well. However, the ceiling vent just can't quite keep up with the shower steam. It's directly above the bath and vents through the loft to a outlet on the side of the house.

Originally, a 12v axial fan was installed circa 1992. This was long since defunct so when I moved in and I entered the loft, cut the PVC duct and dropped in an inline fan with a 25 L/s flow rate. Still, this was inadequate. I've since dropped in a more powerful 52 L/s Blauberg Turbo E.

Better, but... The room still fills up with steam and the walls sweat. What can I do? Would two Blauberg Turbo Es in a series provide more extraction power? Do I need to go to 150mm ducting? Help!

koalakoala

More heating? Mine is much less steamy when the room is warm

FlaatusGoat

koalakoala said:

More heating? Mine is much less steamy when the room is warm

Just had a shower now. The room was already 18c so pretty warm

tacpot12

If the duct is flexible, try switching to a rigid duct. You'll get more through put. You also need to make sure that it is easy for air to get into the bathroom, ideally from somewhere where the air is warm. 

The walls are cold, so steam is condensing on them. Warm them up and you will have less of a problem. Condensation is why the walls and ceilings in shower rooms need to be painted with Bathroom paint, so that the condensation doesn't soak into them, but remains on the surface long enough for the extractor fan to do its work. 

Your Blauberg fan should be connected to a humidistat so that it runs until the room is dry. (this is what I have in my bathroom).

Emmia

I'd say a humidistat is needed, either as part of an extractor fan or separately - the fan will keep going until it has cleared the moisture.

FlaatusGoat

Thanks never heard of a humidistat. Mind linking to an example of what I might need for my installation (there's loads of different types)

I presume this is an additional fan that sits on the vent? My vent grille starts dripping with the shower on any way so I guess I need to push that out rather than purely relying on my inline fan in the loft to do all the grunt work.

The 'on' is currently connected to the ceiling rose so I guess I'd need to wire the humistat inbetween.

Grenage

A humidistat is just a switch that controls the fan based on humidity levels.  It's used rather than a light switch with an overrun timer.

Lorian

Remember even a powerful fan won't be able to move the air if it's a small room with no window or other way for air to be sucked in. You will need to leave the door ajar an inch while the fan is on a decent length of overrun however it's controlled .

Emmia

FlaatusGoat said:

Thanks never heard of a humidistat. Mind linking to an example of what I might need for my installation (there's loads of different types)

I presume this is an additional fan that sits on the vent? My vent grille starts dripping with the shower on any way so I guess I need to push that out rather than purely relying on my inline fan in the loft to do all the grunt work.

The 'on' is currently connected to the ceiling rose so I guess I'd need to wire the humistat inbetween.

We have a wall mounted fan in each of our bathrooms which includes the humidistat in the same device.  Ours are linked to the lighting circuit and so comes on full power when the lights get switched on, but as they're both windowless that's every time they're used. We've got ones like the fan linked to which are really quiet. There's a few in the range which are externally similar so it's worth digging into the specifications to find the right one for your room.

https://www.screwfix.com/p/vent-axia-479087-100mm-4-axial-bathroom-extractor-fan-with-humidistat-timer-white-240v/617gy 

Our fans also come on at a low level if the humidity goes over a certain point, for the first week or so of having them they were running like this almost continuously, and the humidity dropped by about 20% and it's stayed that way.

tacpot12

I have used these at home and in a rental property: E925 Standard Humidistat – MS Electronics

They are a bit expensive now, but they work very well and are very low profile. 

ThisIsWeird

This is all a bit strange, Flaatus.
It's a 'small' bathroom, so presumably air exchange rates will be pretty fast. It's windowless - does that mean no external wall either? And you have a powerful extractor. Blimey.
Such visible steam in the air and on surfaces does usually suggest it's a cold room - what temp is it at?
But, since the new powerful extractor also ain't doing the job, I wonder if it's as Lorian says - the door is just too well sealed? The extractor simply cannot extract from a self-made partial vacuum. 
Q - do your ears bleed when you use the shower? Eyes bulge? Cool.
Could you try what Lorian suggests and see how it compares - the door literally cracked open?
And is there plenty of loft insulation above the ceiling?
Failing that, yes, smooth ducting, going up to 150mm, and a matching - even more powerful - extractor should sort it, and the addition of a switchable humidistat control is also good, if you are currently turning the fan off too early; you may think it's fully dry, but it might not be, so the room begins at a disadvantage the next time. Or, just leave the current fan running for ages - they use next to nothing - with the door cracked open (or even fully open, provided you are confident the steam won't escape into the house instead...)
Oh, how long is the ducting, and how large the exit grill?