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5 Ways to Remove Condensation and Damp Mould


Winter is the time of year when we all hunker down; close the windows and ramp up the heating while enjoying the latest movie or series, filling up on wine and nibbles. It is also usually around this time of year we most experience condensation, and the resulting damp and mould, in our homes. Though it can occur year round under the same conditions.

This is short guide for tenants (and home owners) about what causes condensation and the main ways to avoid it.

The main causes are:

  1. Cooking

  2. Washing

  3. Breathing

  4. Lack of ventiliation

  5. Building fabric failures

This is a 10-15 minute read. The actions are mainly simple steps to tweak in your daily living.

What Is Condensation

Condensation occurs when two differing air temperatures meet. In a home this is typically as a surface barrier like a wall or window.

Relative humidity refers to the amount of moisture the air can hold at a given temperature. The warmer the air the more moisture it can hold. When the temperature is low and humidity is high the air less ability to hold and transport moisture. When warm air meets the cold air we get a saturation point (also called dew point), where the air can no longer hold moisture. This typically occurs in a home on a window or wall which is cooler. The moisture which can’t be held is then released onto the surface. We call this condensation.

<30% humidity is considered dry. This is the climate outside in winter and when we often get chapped lips or dry skin

>30 < 60% - normal humidity range.

>60% humidity – considered wet air. This is when mould and condensation will form on colder surfaces

The below chart show how airs ability to hold water changes over temperature. A drop of temp from 20 to 10 degrees halves the amount of moisture it can hold.

How Does Mould Form

Mould is a form of fungus that breaks down dead organic material. Mould forms and thrives in moist, humid environments. That is one with a relative humidity above 61%. Mould will die out at low humidity levels of less than 30%.

Ideal Living environment at home will have a temperature between 18-22 degree C and a relative humidity of 40-59%. There will be no problems with damp or condensation when a home is maintained at these levels, without any moisture left on the surfaces.

A good way to manage the climate is to purchase an electronic hygrostat. You can get one like in this link from Amazon for less than £10.

A couple of common types of mould found in homes are black mould (Stachybotrys - first foto) and pink brown mould (Aureobasidium - second foto)

Main Causes of Condensation and Damp

1. Cooking

When we cook lot of hot air is produced as steam, along with air born fats and oils. If not extracted effectively at source the steam will reach colder surfaces where the vapour will turn to condensation on the surface. If not removed then this will lead to damp and over time mould will form on the surface. As a guide it is estimated the tpyical family meal can produce in the order of 6 pints of water into the air.


  • Cover pans that produce steam

  • Use the hob extractor while cooking

  • Also open a window in the kitchen to provide a source of fresh air, for the fan to pull through

  • Wipe down residual moisture after finishing cooking

  • Kettle – wipe down steam from boiling and switch it off once starts steaming

2. Washing

Two main ones here are washing yourself, alongside washing and drying clothes in the home. Both of these activities produce large amounts of moisture. If the moisture isn’t wicked off the clothes effectively it can also leave your clothes and home smelling. As an idea drying the typical load of washing in a home can produce in the range of 9 pints of water.


  • When showering - Close bathroom door, open the window and ensure the extractor fan is on to remove the stream and moisture from the air

  • Wipe down the walls and screen after showering to remove water that would otherwise linger and be carried through the house

  • Dry clothes outside when you can on a warm breezy day.

  • Don’t dry clothes over radiators – damages the fabric and leads to localised moisture being trapped

  • Use a heated dry rack in your largest room

  • Don’t dry clothes in your bedroom. This excess moisture

  • Don’t put damp clothes in

  • Always open a window near the dry rack to allow moisture to be carry away

  • When using a tumble dryer also ensure through draft to remove heat and moisture

3. Breathing and night time

The average person gives off around 0.5L of water vapour an hour just from breathing. If there is not sufficient fresh air flow a rooms mix of CO2 will also alter. We breathe out 100x more CO2 than we inhale.

If there isn’t sufficient changes of air as we sleep then the balance of gases in the air will be significantly altered. A high mix of CO2 can lead to headaches and drowsiness when you wake. During the day we are moving around so this tends to be less of a problem. Though if you feel drowsy in the office in the afternoon, it may not be just the curry you had for lunch. However at night time we are stationary in the same room. Over our sleeping time we breathe out a large volume of warm CO2 rich air which will be warmer than our surrounding room temperature. This body of air if not removed from the room effectively will lead to condensation as it reaches and cools on the cooler wall surfaces.

Action Points

  • Experiment with bedroom window open

  • Leave the door ajar if there is less than 10mm gap below it

  • Struggling to manage the humidity then try using moisture traps or a dehumidifier

  • Having moisture absorbing plants in the house can help both climate and atmosphere

4. Regular Room Air Changes

How we manage changes in air through a property have evolved over time. The latest buildings use HVAC systems. Old period properties originally relied on the coal fires drawing air through the building. As heating systems changed to gas boilers extractor fans and vents were added. As a guide older buildings require more manual intervention for ventilation, so the occupant can adjust as their lifestyle and use changes through the day / week. Our properties are equipped with extractor fans in the bathrooms and kitchens, some trickle vents and windows that can be locked on a low opening setting.

Having regular and gradual changes of air through a property allows moisture to be continually taken out of the home and a stable (and comfortable humidity level) climate to be maintained.

Another area where damp and mould can occur is behind furniture which is close to the wall. Here air can get trapped and condensate on the surface and linger. As the temperature of the room fluctuates this provides a fertile breeding ground for mould.

Action Points

  • Open windows at opposite ends of the property regularly and

  • Leave windows ajar (couple of inches) or on first open lock setting

  • Observe if you get condensation and look at what part of your lifestyle is causing the moisture build-up

  • Open the curtains and let light in

  • Struggling to manage the humidity then try using moisture traps or a dehumidifier

  • Having moisture absorbing plants in the house can help both climate and atmosphere

5. Building Fabric Issues

Where there are signs of a leak in the building report these and get them repaired at the earliest opportunity. Typical points causing leaks are sources of water (such as sinks and radiators) or construction that keeps water out failing, such as the roof, gutter or waste down pipes, rising damp through faulty damp proof membranes. These later issues normally show up in the corners of ceilings or large wet patches on the wall.

Building leaks typically appear from nothing and reveal a sudden localised wet issue. It is rare to see mould in these issues as the area is too wet and often has waste chemicals which kill the mould. It is more often salts bubbling to the surface from the masonary / plaster work. So this is a good easy way to distinguish the cause.

Action Points

  • Investigate any suspected leaks - see if it is condensation related or an actual leak such as a dripping tap or item has been left running etc

  • Report a leak that is related damage to the building as soon as you find it

This 30minute video gives a great overview.

How to treat mould in specific areas

If you find that mould has formed in part of your property then alongside resolving the cause, it will be necessary to get to clean the mould off the surface. Here are some common ways you can treat it.


Want to know how to get rid of mould in a bathroom? A cleaning solution is an excellent option for smooth bathroom surfaces such as sinks, tiles and bathtubs. Whilst wearing protective gloves, spray a cleaning solution onto the area affected with mould and use a sponge to wipe the mould away. For tighter spaces you can also use a toothbrush for trapped mould.


Mould on kitchen cabinets can be cleaned using a homemade solution with equal parts water and detergent in a spray bottle. Next, use a toothbrush or kitchen scrubbing brush to remove the mould.

Walls and Ceilings

To get rid of mould on walls and ceilings, vacuum as much of the surface mould as possible (to prevent airbourn spores), then wearing a face mask you will usually need a paint scraper to remove the paint barrier and access the mould to remove it. Once main mould on the paint or wallpaper is rubbed off , use mould removal spray and a firm sponge to remove the mould.

Cleaning products to use

Tea Tree Oil - this is a natural antiseptic and disinfectant which can be great to clean mould or mildew. Dilute 3 to 4 drops of the oil per litre of water. soak the issue area or surface, wipe and then rinse off. If unsure how the material will react, test on a small area first, to avoid ruining the material.

E-cloths are microfibre cloths designed to remove more than 99% of bacteria. All you need to do is rinse the cloth and wring it out, draw it across your dirty surfaces and wash it afterwards with hot water or in the washing machine.

White vinegar can be great for some jobs, such as descaling kettles and shower heads, and leaving streak-free windows. Don't use vinegar to clean mirrors, stone or granite kitchen countertops, or wooden or stone flooring, as it can make them lose their shine. Don't use it for knives, washing machines or dishwashers, either, as it might cause damage.

Baking soda works wonders for stains and smells, it's non-abrasive and saves you having to scrub or use bleach. You can use it to wipe away old food residues from the inside of a fridge, for example, or you can add it to pots and pans to help lift stubborn, crusty foods.

Commercial anti mould sprays - there are various bleach based sprays that can help remove problem moulds, such as Astonish Mould & Mildew Remover or other brands, a review is in this article here.

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