Exact temperature to prevent bathroom mould growing this autumn
With a new season on the horizon, homeowners have been told keeping the smallest room in the house at one temperature will stop mould from growing
As summer gives way to autumn, many householders will be dreading one thing. The cooler, damper weather can see mould rear it's unwelcome head again and it can be a battle to keep the fungal growth at bay with many people having to constantly clean to keep on top of it.
The combination of cooler outdoor air and increased indoor humidity creates the perfect conditions for mould to thrive and our bathrooms suffer as it's a place where moisture levels are naturally high. But experts say that there is an exact temperature to keep the smallest room in the house at which will stop mould in its tracks.
The science behind autumn mould growth is surprisingly straightforward. When warm, humid air from hot showers hits cold bathroom surfaces – particularly walls, windows, and tiles – condensation forms almost instantly.
During autumn, this problem gets worse. Outside temperatures drop, meaning your bathroom walls and windows become much colder. Meanwhile, indoor humidity levels often increase as people start using heating systems and spend more time indoors with windows closed.
Persistent mould growth indoors is not only unsightly, it can also be a health concern. The NHS says you are more likely to have respiratory problems, respiratory infections, allergies and asthma if your home has mould.
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Babies, children and older people are more sensitive to damp and mould as are those with existing skin conditions like atopic eczema, those with a weakened immune system such as people having chemotherapy.
Peter Jones, Director of ADI Leak Detection, a specialist company focusing on water leak detection and property moisture issues, said that temperature control should be the 'first line of defence' in keeping mould at bay.
He said: "The key to preventing autumn mould isn't just opening windows or running extractor fans. Temperature control is actually your first line of defence, and most people have no idea what temperature they should be aiming for."
The expert with over a decade of experience dealing with moisture-related property damage across Scotland, England, and Wales, said the magic number is 19C.
Peter said this temperature combined with effective ventilation is key in the cooler months.
He explained: "Nineteen degrees might sound overly specific, but there's solid reasoning behind it.
"At this temperature, your bathroom surfaces stay warm enough to prevent condensation from forming when you shower or bathe. Go much lower, and you're asking for trouble.
"Temperature control is something most homeowners completely underestimate when it comes to mould prevention. In over a decade of dealing with water damage and moisture issues, I've seen countless properties where expensive mould problems could have been avoided with simple temperature management.
“The 19-degree rule is based on physics, rather than just comfort. When your bathroom surfaces stay consistently warm, moisture simply can't condense and settle. I always tell clients to think of their bathroom temperature as insurance against costly mould remediation down the line.
“What surprises people most is how quickly mould can take hold once temperatures drop. You might not notice anything for weeks, then suddenly you're dealing with black spots on walls and ceilings that require professional treatment. A small investment in proper heating and monitoring pays for itself many times over when you consider the alternative costs."
He has suggested four ways to hit the target temperature in your bathroom.
1. Use A Bathroom Radiator Or Heated Towel Rail
Installing a dedicated bathroom radiator or heated towel rail helps maintain consistent warmth. In addition to drying towels, they keep wall temperatures up, which significantly reduces condensation risk.
2. Smart Heating Scheduling
Set your heating to come on 30 minutes before typical shower times. This pre-warms the room and surfaces, preventing that shock temperature difference when hot water starts running.
3. Underfloor Heating
While more expensive to install, underfloor heating provides even temperature distribution and keeps surfaces consistently warm. “It's particularly effective because it heats from the ground up, warming all surfaces gradually,” notes Peter.
4. Insulation Improvements
Poor insulation makes temperature control much harder. Adding insulation to external walls or upgrading windows can help maintain that stable 19-degree environment without constantly running heating.
Peter also suggests investing in a simple digital thermometer to track your bathroom temperature. "Most people guess their bathroom temperature, but you need to know for certain. A basic digital thermometer costs under £10 and takes the guesswork out of mould prevention."
Place the thermometer away from direct heat sources, but where you can easily check it. Aim to maintain 19 degrees even when the bathroom isn't in use.