Condensation issues

Welderpaul · May 18, 2023

Ensuite bathroom - bath and shower, pot and basin. Solid walls, one window.
There's an issue with condensation and it's caused black mould to form on the walls.
Nothing obvious where damp is getting in. House is pretty bomb prooof.

The forum's thoughts on the proposed solutions would be most welcome :hug:

. Ideas along the lines of reboarding the walls with insulated plasterboard, vapour barriers etc are not the route they can go down.

1. Extractor fan is wired to the lights so only comes on when the light is on. No overrun either - exchange for humidistat fan.
2. Retro fit trickle vent to UPVC window
3. Fungicide treatment to kill off spores
4. Make good to walls and paint with a specific bathroom paint with a fungicide additive - Mention has been made of using Anticon thermal paint but this seems like smoke and mirrors stuff? Current paint is flat/matt which isnt helping the issue.

Any thoughts?

addjunkie · May 18, 2023

I had a real issue in the ensuite in one of our holiday cottages….biggest fan I could get in. With over run. Also ask guests to leave shower door open once finished to allow air to circulate. But the space is well insulated so no cold bridging.

You could line to room with wipe clean shower board, only 6mm thick, wouldnt stop condensation but would be easy to clean / dry.

Air circulation is key.

OJCar · May 18, 2023

How about increasing the background heating in the ensuite and well as improving the ventilation ?

voipio · May 18, 2023

Wall surface temperature is falling below the dewpoint of the air in the bathroom. The solid walls are probably the main issue but, if you can't do anything about those, then heating the room is one option, and removing the moist air is another (or both in combination). Is the bathroom close to the kitchen, or is there a clothes dryer/airer kept nearby?

tom2207 · May 18, 2023

ventilation will help ,,, in any and every form , overrun on fan is a must at the minimum , its just a product of surfaces being colder than others ,,, its a pain and the persistent problem with rentals , tenants wont ventilate as its letting the heat out and so it starts

brightspark · May 18, 2023

its preferable to get a decent flow inline timer fan and the inlet over the shower if u cant get above a decent timer fan through the wall as near to shower as possible and dont put an isolator switch in if its rented otherwise they just turn it off and it defeats the object

gaz1 · May 19, 2023

Welderpaul said:
Ensuite bathroom - bath and shower, pot and basin. Solid walls, one window.
There's an issue with condensation and it's caused black mould to form on the walls.
Nothing obvious where damp is getting in. House is pretty bomb prooof.

any pics available

wheres the damp

low, medium or high up the wall

you state soild walls whats your version of solid wall

old through style, soil filled style or gap inbetween the walls as each one is different

no house is bomb proof with water it will find a way into your property if things have been neglected

the main thing is find the cause of the issue

Erie Fred · May 19, 2023

Move to Arizona....I hear it's a Dry heat.....

Pigeon_Droppings2 · May 19, 2023

The silent fans these days are excellent...just got one in B&Q clearance for £30.

I'm not 100% sure whether the fan is silent...or it's my hearing that's gone but on the lower setting I can't here it.

The one I got was by Vent Axia...they do over run ones and also humidistat too. On the lower speed setting I couldn't hear it.

Apparently it's only 12 dB....noisy ones people will tend to disable I reckon.

MattF · May 19, 2023

Pigeon_Droppings2 said:
I'm not 100% sure whether the fan is silent...or it's my hearing that's gone

mtt.tr · May 19, 2023

fan heater and a window ajar

gaz1 said:
any pics available

wheres the damp

low, medium or high up the wall

you state soild walls whats your version of solid wall

old through style, soil filled style or gap inbetween the walls as each one is different

no house is bomb proof with water it will find a way into your property if things have been neglected

the main thing is find the cause of the issue

It's a bathroom it will be from the shower.

willie.macleod · May 19, 2023

In addition to all your suggestions I'd add a electric towel rail to provide base level heat and warm the walls/ceiling to increase the dew point.

prepman · May 19, 2023

addjunkie said:
Air circulation is key.

Gets my vote.

addjunkie · May 19, 2023

willie.macleod said:
In addition to all your suggestions I'd add a electric towel rail to provide base level heat and warm the walls/ceiling to increase the dew point.

On a timer to fit around your lifestyle. Dear things to run 24x7

prepman · May 19, 2023

Dehumidifier was my solution. The molsieve type is quiet (except for fan). Old stone walls condense out anything produced in the kitchen/bathroom.

Gareth J · May 19, 2023

Used to have a small ensuite that was forever getting mouldy/damp. Also had one stone wall.

Things I tried before mould stopped.
-big fan, with overrun
-humidistat controlled fan as well
-opening window after showers

Then had a big refit;
-Replastered stone wall with lime based insulating render
-topped up the partially filled cavity with EPS beads
-Insulated the lintel (thinnest bit of the wall there) with PIR and PIR backed plasterboard
-insulated the block external wall, which was also often mouldy, with rockwool behind panelling below sink and insulated plasterboard above
-AND, crucially I think, we now always squeegee and dry the shower.

Is now drier than ever before.

Terrible grainy photo but hopefully gives the idea.

Things I think made the biggest improvements in order of priority;
-The old stone wall plaster was put onto a layer of corrugated bitumen that had a very small airgap behind. This connected floor void to loft to wall cavity and, on removal, it was obvious it was blowing a gale behind there. Great for keeping the wall dry but terrible insulation - might as well have been a room made of 1" of plaster on cold, windy days. Stopping that airpath and, where possible, fully filling the cavity on the mirror/sink wall (mould used to highlight missing areas of fluff) has allowed the thermal mass of the stone wall to help buffer temperature swings and in general improved insulation.
-wiping the shower.
It's a pain but, when you see the amount of water squeegeed down the drain, that the room would otherwise have to deal with, it's huge.
-The big extractor fan above shower.
Essentially, the room only has to deal with moisture you bring out of the shower on towels and bodies. The fan has enough oomph to capture all vapour from shower in use. With a door gap to match.
-The insulation render.
Not because it's particularly insulating - theres a max of 50mm there and it's not a great insulator. But it has an incredible capacity to buffer water. Some condensation on chilly days, around the window reveals is inevitable this stuff is brilliant at buffering moisture - absorbing then evaporating. It feels like you could throw a glass of water at the wall and none would hit the floor. (A clear exaggeration). Is painted with whitewash plus a bit of whiteish pigment.
-Insulating the lintel;
No brainer, was the thinnest bit of wall and the coolest spot. Have lost nothing by doing it and gained a lot.
-The panelling;
Hides pipework and insulates. Win win.
-Insulated plasterboard behind the (heated!) mirror; Yea, an improvement, but that's a fluff filled cavity wall anyway and I question whether it was a good idea. The screws fixing it occasionally condense a bit of dampness. I should take them out and rely on gun foam I think.
-Humidistat fan;
It still cuts in when the towel rail fires up but I doubt it'd be a problem without it now.