Posted 5 January 2024

Mould on walls

Hi, I keep getting mould on the internal walls which face the outside. I spray it with anti mould spray and it goes, but within a week I'm getting it again!

Presume it's not a damp problem and just to do with temperature of central heating and due to drying clothes indoors, but is there anything I can do to stop it? Should central heating be set to a certain temp all the time instead of going up to 23 and back down to 20 during the day?
Thanks

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5th Jan
Opening windows when you're drying clothes on radiators should help or try a dehumidifier
5th Jan
Personally, I pick a room for drying, turn off the heating in the room, close the door and leave the windows open.
5th Jan
Stop drying clothes indoors if you can, or get a heat pump dryer if you're worried about the running costs of a normal dryer.

If you simply don't have space for a dryer then a dehumidifier would be really helpful but ideally put all your clothes in a single room with the dehumidifier and leave the door closed.
5th Jan

A dehumidifier is the answer to your problem. They are excellent for taking water out of washing, you don't even need the heating on. I do an extra spin on my washing in the winter and pop them on the airer in the same room as the dehumidifier and they dry great. Best to use the smallest room you can.

Then move the dehumidifier around your home to each room as required when your not drying the washing.

It's a great investment as it saves damaging your property and they are cheaper to run than your heating.

The 99p mould sprays in the like of B&M and Home Bargains are surprising effect if some mould does still appear.
Author
5th Jan
Can you recommend one please? How do I know where to keep moving it to?
5th Jan
Whatever you do don't leave a window open with a dehumidifier running.
5th Jan
Buy one of those gadgets that checks your moisture levels from Amazon

ThermoPro TP50 Digital Thermo-Hygrometer Indoor Room Thermometer with Recording and Climate Indicator for Room, Climate Control Monitor : Amazon.co.uk: Garden

And move your dehumidifier around the house accordingly.

My daughter's room had mould and condensation every morning. Used the kercher to wipe her windows every morning. Two days running the dehumidifier, wiped the mould down with a cloth and an anti mould spray - all sorted now.

She had a reading of 96 humidity last month - around 60 now
5th Jan
It is not a problem caused by the house but caused by the person drying the clothes.

To solve the issue is simple & involves one of these solutions:
Dry clothes outside
Dry clothes in a tumble dryer preferably one that is vented outside or collects water which you can regularly empty .
Dry clothes in the bathroom or kitchen & leave the extractor fan on & the door shut.
Dry clothes in a nominated bedroom with the window open & door shut.

Or buy a dehumidifier & use that in a room of your choice with the door shut.

Stating the obvious but if you leave the clothes in a room with the door shut & window open or an extractor on then turn the heating off in that room.
Author
5th Jan
I dry clothes in the lounge and get no mould in there which is why I'm not sure this is the reason
5th Jan
Opening windows is counter productive if the outside humidity is greater than inside . Outside is typically 80-95% at this time of year unless the temperature drops to near or below freezing .
6th Jan
It doesn't work like that. The humidity measure is relative humidity and it is relative to the temperature.

Air at 20 degrees and 50% RH holds roughly 7g of water per cubic meter and air at 5 degrees and 85% RH holds roughly 4g of water per cubic meter.

Thus opening the windows today allows air containing less actual moisture (but a higher RH) in and pushes air containing more actual moisture (but a lower RH) out. As the colder air warms up inside, it's RH will drop.

This morning the RH in my spare room was 72% and I opened the windows in the house for 1 hour and it dropped to 64% (which is much more efficient that my dehumidifier could ever do in the same time). The outside temperature is 5 degrees at 89% RH.
5th Jan
Always other options OP
5th Jan
Ventilation is key. Mould grows on damp surfaces, damp surfaces are caused by excess moisture in the air condensing on cold surfaces. So either warm up the surfaces which will reduce the humidty and thus reduce the amount of moisture in the air or keep air circulating. A dehumidifier is an expense solution.
Note that your breath has enough moisture to cause mould problems if your house is not properly ventilated. My parents went for a forced air system in their new home.
5th Jan
Every morning when you wake up that wall will likely be wet (because it's a colder external wall and the water in the air is condensing on it over night when the temperatures are colder and the heating in on less), wipe it dry with a towel and put the towel out to dry, you then won't have mould on that wall again
Author
5th Jan
I was going to get a dehumidifier but short on space. If I place it in the kitchen, it won't take the damp out of the bedroom and vice versa though.
5th Jan
They're the size of a small suitcase. You move them from room to room as needed.
5th Jan
This is a ventilation issue.
It is totally understandable to get rid of draughts to help to keep temperatures up but that means a lack of air moving moisture through evaporation.
We have one wall by the front door which gets cold and due to the way the house is laid out gets no airflow. We use one of those cheap moisture traps just to keep it dry and it seems to work a treat.
However the rest of the hosue is fine as we have ventilation through the walls as well as chimenys.
5th Jan
Buy a dehumidifier for around £100. I was so impressed I bought another so have two. Amazing amount of water I pour out the tank every few days. We run for a few hours every evening and to dry washing. (edited)
5th Jan
You will always pull water out on the air with a good dehumidifier in the UK regardless of its use.

But I am sure you know that. Saying that though. It really is a must for anyone drying clothes inside in the winter who wont close the door & open a window. What model do you have? I might buy one for a friend of mine who gets issues in an upstairs bedroom due to the way they dry their clothes. (edited)
5th Jan
Have to say having an extractor fan in my bathroom is a real boon for drying clothes op
Ventilation/circulation is key here
and strike down any mould with a vengeance !
wash any clothes/bedding that smell 'musty' or chuck
5th Jan
Window opening and trickle vents have a limited impact. A small dehumidifier running when drying washing and a few hours in the evening is the cure. We were late to the party.

Our two going now.
5th Jan
I agree that trickle vents are useless in solving the problem but "properly" opening a window & shutting the door will work just as good, if not better, than any dehumidifier because the air circulation would be much better. Unless you stick a big fan in there to go with the dehumidifier. We will have to disagree with that one.
6th Jan
Use Positive input ventilation. Even if the air is saturated from drying clothes inside, PIV will be pushing the humid air out of the house through trickle vents etc.