How to stop condensation
Firstly If you’ve found this page I’d like to think you would like to fix your condensation problem, yes? I hope so because you would be amazed how many people listen to good advice then ignore it.
Condensation & mould, If you really want to beat it you have to understand it”
The ‘how to cure condensation’ video, if you haven’t seen it before it’s worth having a look, always do the easy stuff first.
Condensation cure – This video on How to stop condensation will take you through nearly all of the basic steps in case you haven’t already seen it. Please read the rest of the article for lots more good tips and links.
How to cure condensation
I’ve been advising people for many years and because in my line of work ( Roofing ) condensation mould on ceilings and walls is often mistaken for a leak and I get called in to investigate. I’ve quite literally seen thousands of mouldy and damp properties.
Here are just some on the clients I’ve looked at properties for…
- Private home owners
- Estate agents
- Building society’s pre-mortgage surveys
So now you know I might actually know a little about the subject and I’m not just cut, copy and pasting second hand knowledge from other websites who have also done the same, let’s look at the most common causes covering 90% of domestic condensation.
Condensation on double glazing – Meet condensation. I’m sure everyone is all too familiar with this, the classic condensation on a window. Seen all over during autumn and winter, especially after a good nights sleep.
How to tell the difference between a leak and condensation stains
A Water stain on the ceiling – A large but typical water stain on a ceiling, the brown tea colouration is the hallmark of a leak as compared to the black mould or shadowy look of a condensation mark. This holds true in 80% of cases.
Right half – The shadowy wet look of condensation and some mould.Click to enlarge
How to paint over condensation marks and mould stains
Please click here to see my how to clean black mould page that includes correct procedure for getting rid of water stains, condensation marks and black mould stains.
What is condensation ?
Condensation cycle – In this case moisture from damp clothes evaporates into the air and is suspended there until it reaches dew point when it comes into contact with a cold surface such as glass, It then turns back into water.
Click to enlarge
Condensation is caused by airborne moisture, minute particles of water suspended in the air, created by every day activity inside the home. Think of it as an invisible indoor fog that turns back to water on contact with a cold surface.
If you breathe on the surface of a mirror or glass you will see a fine fog form on the glass, that’s condensation. A few seconds later and its gone, evaporated back into the air to join the rest, it’s as simple as that.
What does mould look like inside the home ?
Mould on walls and mould on ceilings – These are typical black mould mark caused by condensation. A leak almost never creates this type of mouldy mark, a leak almost always makes a light brown looking stain.
Click to enlarge
Click to enlarge
Black marks above skirting boards – Yet another classic. Black mould behind a bed, and the bed situated close to the wall hinders the air flow. Quite often seen in properties let to students, or family homes.
Click to enlarge
Click to enlarge
What causes condensation ?
In times gone by houses would have had single glazing, air vents built into the brickwork and open fireplaces that would have literally drawn in the air outside. Whilst this may have been a lot colder to live in, the air was constantly refreshed.
Welcome to the present day, now we try to keep the heat in as much as possible, double glazed windows, doors, draught excluders, insulated cavity walls and roof spaces. It’s all about saving energy and keeping the heat in as much as possible. Unfortunately that also means keeping the air in no matter how damp or stale it has become. Also adding to this are showers, unvented tumble driers, airing the washing indoors and cooking, every activity just mentioned including breathing will add vast amounts of moisture into the air.
When the clock matters – To make matters worse these activities are normally concentrated at the same time of the day, evenings. We get home from work, cook, shower etc. then sleep.
Just for good measure in the morning we then close all the windows and doors locking the damp air in, turn off the heating and go out.
Black mould on walls and black mould on ceilings
OK so we have all this airborne moisture but it wants to condensate, its looking for a cold surface where it reaches dew-point and turns back into liquid water. Any cold surface will do, but since these days houses are nearly all double glazed and insulated it normally ends up on an outside wall near the ceiling, but other places it commonly shows itself are…
- Above skirting boards
- Inside cupboards
- Behind beds
- Behind wardrobes
- Outside walls – usually singe skin solid walls
- Window surrounds and windows
To clean mould off surfaces like walls please read the mould section further down.
Top contributors of mould and condensation
Drying washing indoors – It gets cold the washing no longer dry’s outside, so on the radiator or onto an airer it goes. Now bearing in mind an unvented tumble drier can produce up to 7 Litres of water per day you can see we’re off to a bad start. (Read about de-humidifiers further down the page for more good tips)
- Hot showers and Baths – Not many people can see themselves in the bathroom mirror after a nice hot shower can they? Steam you can see, that’s going to be a lot of airborne moisture you cannot.
- Cooking – Yes those steaming pans are helping to top up the moist air nicely and your frozen pie is cooking in the oven, where do you think all the water is going?
- Breathing – Now I know this can be tricky to cut down on, but one person’s lungs can expel up to 4 cups of water per day.
- Boiling a kettle – Lets have a cup of tea while we add up all this moisture.
- Multiple occupancy – just when you thought it couldn’t get any worse…The more people living and doing all of the above activities inside a house the more problems you will have. Multiply all the above by the number of occupants.
I know what you’re thinking, ‘ I’ll just open the window for an hour ‘ well, while it does help we need to get rid of litres and litres of water here, you’re not letting the cat out.
Out of control condensation
This is when condensation is so bad that the walls and plaster are damp to the touch or are literally wet to the touch. I have seen walls actually running with water, and drips trickling down the wall onto the upstairs bedroom floor. This is where the condensation is so bad that it makes the plaster and brickwork wet internally, this then conducts the cold from the outside even better than before. This has now become a vicious circle and it begins to run away with itself. You do not want to be here!
If this is the case you hire or buy a good dehumidifier to get it under control, buy a good humidity meter , follow the advice below and be methodical and constant in your approach. Get your property checked by a reputable firm if you suspect rising damp or roof and gutter leaks may be a contributing factor.
How to cure mould and condensation
Condensation cure – Yes, It can be done but, how effective it is will determine how serious you are, and how many people live in the property. If its multiple occupancy then everyone living there has to be onside.
- Do not dry washing indoors – A vented tumble drier is king and will blow all the moisture from the drying process down a pipe and outside the house. A condensation tumble drier is second choice but you must empty the water container often.
- Baths and showers – If you have an extractor get a good one with high flow rate some even work on humidity levels. Google is a good place to search for ‘high capacity bathroom exhaust fans’. Secondly open the window, and turn on the extractor too if you have one. Thirdly open a window whilst in the shower and for at least one hour afterwards, however this may not be as effective during the winter months as outside humidity increases.
- Cooking – Put lids on the pans, not only will your food cook faster but you will capture almost all the moisture and save energy at the same time. Win Win.
- Breathing – Our old friend. Open the windows at night if possible, preferably still in a locked position if the window is of a size to enter externally, or on a ground floor.
- Multiple occupancy – It’s no good acting alone to beat mould and condensation you all have to pull together, all the time!
- Boiling a Kettle – If you follow all the steps above you can probably boil that kettle now.
- Buy a Dehumidifier – A very powerful addition to the above measures, not a total replacement. Get one that’s quiet and cheap to run – read my article on the best dehumidifiers that I update every year with the help of landlords and estate agents, and read some reviews first. A dehumidifier can be coupled with a timer or left on, but do not run it with open doors or windows or you will be drawing air in, drying it and paying to do so.
Do dehumidifiers work ?
Dehumidifiers work – A good small to medium size dehumidifier can remove up to 12 litres of water per day from the air.
A fairly standard small dehumidifier is a very effective tool if used intelligently. For most domestic situations one or two small, quiet and economical to run dehumidifiers solve almost all winter condensation and mould problems.
A dehumidifier really comes into its own in the winter months and can be a game changer if used correctly. These are useful because sometimes opening a window becomes useless in the UK, even as early as October outside humidity can reach between 70 – 90%. Opening the window to let damp air in to a damp house isn’t going to help anyone. See how to buy and use the best dehumidifier
For up to date and live humidity levels from the BBC click on
Humidity UK and search for your town or city in the search box.
Humidity levels – Here we have the UK ( London ) average daily low figures for humidity. The months shaded red depict the worst months for condensation. These figures are considered good and it can easily be as high as 90 – 100% any month on a bad day.
A good dehumidifier can keep a normal 3 or 4 bedroom house at around 50% humidity, also bear in mind that dry walls, plaster and brickwork will mean a warmer house because dry air and walls insulate better. This will mean lower energy bills. Win Win.
Drying washing indoors in winter
If you have a good dehumidifier you could actually use it to dry your clothes instead of using a tumble drier in winter if you don’t have one. By placing the dehumidifier in proximity to the drying washing it can remove all the evaporating water at up to 25% of the cost of running your tumble drier. This is a super effective and practical method when using a dehumidifier with a built in laundry function as talked about in my article on the best dehumidifier page, if you want to see what to use and how best to deploy it have a look there.
Drying washing with a dehumidifier – When using this setup with a standard dehumidifier some experimentation may be required to find the best placement for the dehumidifier and clothing.
Humidity levels in the home
Indoor humidity is something no one gives a thought to until they have a problem. If you want to monitor your progress or try to setup the ideal environment you may want to consider buying a humidity meter. Like most things in life price separates an accurate meter from an inaccurate one. Most indoor weather stations have an inbuilt humidity meter and its better than nothing, but getting an accurate reading from it can be questionable.
Indoor humidity test – Amazon always seems to be a good starting point because you can read reviews left by previous customers, search for Humidity Meter or Hygrometer.
What is the correct home humidity level ?
This is a good question and I’m sure if you Google it you would find all sorts of figures thrown around by Herbert’s at home but not many factual answers, so have a look at the U.S. Environmental protection agency data in a chart as supplied here.
This recommended humidity of 40% is a sweet spot, and a very good target to aim for, even if you stray in and out of it a little.
How to clean mould
There is no shortage of large companies willing to sell you products to clean mould in the home, in fact it’s become big business. A lot of the marketing is aimed at frightening you with possible disease then selling you an expensive cleaning solution or paint that isn’t needed. But what they seem to always skip over is solving the problem first. But if you want to see no nonsense cleaners ranging from free to not very expensive professional solutions see our page on how to clean black mould, linked below.
- How to clean black mould – Clean mold and mildew
- Best dehumidifier – What to buy and how to use, stops condensation and mould