Black mould Part 3 - Condensation

22nd Jan 2017

Hello everyone and Happy New Year to you all. Here’s to a prosperous 2017 for you all filled with love and happiness in your homes. In today’s blog, I’m going to examine one of the major causes of black mould in homes - condensation. We’ll look at what condensation is, how it attributes to mould build-up and what you can do to prevent it.

Condensation is a growing problem in the modern household. For some time now, the focus has been on the energy efficiency of our homes. The era of ‘smart’ technologies has brought us many advances and none more so that in the home. The majority of items in your home can now be controlled from your smart phone - everything from your lights and heating to your TV and kettle. As the technology has improved on the items contained within our homes, so too has the materials used to build them. Nowadays we all have double glazing as a minimum. We have continually growing layers of insulation in walls and ceilings and better seals around openings like windows and doors. All of this has been improved over time for the purpose of energy efficiency. The result of this is two-fold. First of all, it saves the homeowner money as heat from within the property isn’t lost to the outside and secondly it stops the colder external air from penetrating the property (a draught to you and me!) One thing this has brought about however, is the increase in black mould as a result of condensation.

When we go about our daily lives at home, we produce a fairly sizeable amount of water. The average person produces 800ml of moisture per day through respiration and perspiration. Attribute that to a four bedroom home and that’s a lot of moisture! When we shower, cook, dry clothes or even breathe we are producing moisture into the air which has to go somewhere. Previously in the draughty house, this water vapour would simply be removed from the property as the external air filtered through it. However this isn’t the case anymore. Due to the energy efficiency of our homes, this moisture is now trapped inside with nowhere to go. 

As the moisture is trapped inside, it begins to attach itself to surfaces. These are mainly walls and ceilings however it can also land on clothes and furniture if they are left undisturbed for a period of time. The humid air deposits it’s water vapour onto these surfaces and condensation begins to form. As you continue to heat your home, you are creating the optimum conditions for mould growth and soon you will start to see the black patches appearing in various areas.

It would be interesting at this point to consider where the mould is in your home. I’m sure you are reading this blog because you have encountered it somewhere - is it in your en-suite that has no window which you shower in every day? The kitchen where you often boil water while cooking with no lid on the pan? Or perhaps a spare bedroom that is used to dry your clothes because you live in a flat and have no garden? If so, condensation is the likely cause. Don’t worry though - the good thing about this cause of mould growth is as it’s you that produces the moisture that causes it, you can make the changes to eradicate it.

The single most effective way to remove mould caused by condensation from your home is to vent it. Keep extractor fans running as long as possible after taking showers, open windows while cooking or while clothes are drying and if you have modern windows with the small ‘trickle’ vents at the top of the frame, keep these open as often as you can. This will allow fresh air to circulate through your home and remove water vapour. These changes may seem fairly small and simple, but they are the single most effective way to avoid condensation-related mould build-up in any property.

Right now you know the changes to make to stop the mould from coming back but how do you remove the mould that is there already? To remove the mould, clean it thoroughly with a specialised mould cleaner containing bleach (If the mould wipes off the surface easily, that would suggest that has landed on it from the inside and therefore condensation is definitely the cause of your problem!) Once clean, go over the area with an anti-fungal agent to help prevent the mould from re-appearing in the future. You may find in some areas like bathrooms for example, the mould penetrates grout or sealant. In these cases I would suggest removing the effected materials and replacing them as this will be far easier than cleaning in between each of your tiles with a bleach coated toothbrush! You may also have to re-paint areas of your walls and ceilings due to the cleaning process. Please don’t be tempted to just paint over the mould as you are only masking the problem and it will return - in greater volumes!

I hope this blog has made you think about the way you live in your home and how you may be contributing to a mould problem. The good thing about condensation related mould as I’ve mentioned previously is that as it’s you that causes it; you making small, simple changes can prevent it.

As I’ve mentioned in all of my blogs, I’m happy to field any questions or comments relating to them. You can direct them to me by email ( or via your preferred social media platform. If having read this blog and thought about the rooms in your home affected by condensation, please check out my blog on Penetrating Damp ( as this may be the cause in your case.

That’s it from me for now. I hope this blog has been beneficial to you and you can now look forward to a mould-free 2017 in your home!