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Condensation Control, The Cause & The Solution

Posted by: Neil Marsden Snr on 18/01/2017


A Simple Explanation of Condensation-The Cause and The Cure.

With the colder spells of weather, condensation is becoming an increasing problem for many homeowners. Unsightly mould growths are appearing in wardrobes, kitchen units, around windows in bedrooms and in any areas where air circulation is minimal.

The cost implication can be significant with damage caused by the mould growth affecting wall coverings, items of clothing, leather and suede goods are particularly vulnerable. For many dealing with the mould can seem like an impossible task. No sooner have you cleaned the offending mould and it re-appears within days or weeks.

Simply cleaning away the mould is not the answer. You must deal with the cause of the mould to achieve a long-term solution.

We are experiencing increased levels of condensation in our homes. This is a direct result of our lifestyle.

I am of the older generation who grew up in houses that had open fires (excellent ventilation), single glazed (draughty) windows, wooden doors (which never fitted properly), Bathed once a week (Sunday night before going back to school), did our washing on a specific day by dragging the twin tub washing machine close to the back door etc etc. In other words, we produced minimal moisture laden air whilst having the maximum of ventilation (better known as draughts). Times were hard but the one thing we did not suffer from was condensation (we were more likely to suffer from hypothermia).

What do we have today? Double glazed windows, UPVC doors, 300mm of insulation in the roof space, cavity wall insulation, extensive draught proofing, no open fires, central heating (drying clothes on radiators), showers which we use daily (or baths), washing machines, tumble dryers, etc. In other words, we produce huge amounts of moisture laden air with the absolute minimum of ventilation to remove it.

Therein lays the problem. We live in insulated boxes which are very comfortable but can be very unhealthy.

There are dozens of retrofit solutions available to deal with condensation in our homes such as Positive Input Vents, Heat Recovery Systems, Passyfier Vents, Dehumidifiers, upgrading mechanical extraction etc. Some are better than others. The honest answer is that we can significantly reduce the condensation levels by making a few adjustments to our lifestyle.

What causes Condensation?

There are 4 main factors that cause condensation:

• Too much moisture being produced in your home

• Not enough ventilation

• Cold surfaces

• The temperature of your home

You need to look at these factors to cure a condensation problem.


2 people at home can produce = 3 pints or 1.7 litres

A bath or shower = 2 pints or 1.13 litres

Drying clothes indoors = 9 pints or 5.11 litres

Cooking and use of a kettle = 6 pints or 3.40 litres

Washing dishes = 2 pints or 1.13 litres

Bottled gas heater (8 hours use) = 4 pints or 2.27 litres

Total moisture added in 1 day = 26 pints or 14.8 litres

It is not difficult to imagine the damage 26 pints of water can cause and the need to reduce the generation of moisture vapour.

Condensation is the cause of dampness in properties that is most likely to be misdiagnosed as rising damp. Condensation often occurs at the base of the wall and can look very much like rising damp.

A recent industry which has appeared over the past 4-5 years is the emergence of ‘Mould Remedial Companies’. They promise to come into your property and treat the mould with some magical chemical which will kill it and solve your problem. Do not be fooled. Simply removing the mould does not solve the cause of the problem and without a doubt the mould will re-occur and you will end up paying more money for a pointless treatment. Deal with the condensation issues and you will eliminate the mould growth.

What can you do to reduce the moisture in your home?

A few simple tips that will reduce moisture are: -

  • Hang your washing outside is at all possible. If this is not possible, hang it in a bathroom with the door closed and a window slightly open or an extractor fan switched on. Even better, purchase a dehumidifier and place it in a spare room with your washing hung to dry. The de-humidifier will significantly reduce the amount of moisture which will become airborne. Do not dry washing on radiators or in front of convector heaters.

  • Always cook with pan lids on and turn down the heat when the water has boiled. Only use the minimum of water for cooking vegetables. Use your cooker hood (if it is vented to outside) when using your hob.

  • When filling the bath, run the cold water first (approximately 2-3 inches deep then add the hot water. It will reduce the steam by 80-90%
  • If using a tumble dryer, make sure that it vented to the outside. A condensing type will be useful but a vented dryer is far better.

  • Do not use your gas cooker to heat your kitchen. It produces moisture when burning gas.

  • Avoid the use of bottled gas heaters. They produce approximately 8 pints of water from an average sized gas cylinder.

  • Upgrade your existing extraction fans to ‘Constant Trickle and Boost Fans’ (CTB Fans) which will monitor the humidity and boost to reduce the levels when needed. If you do not have extractors in the wet rooms i.e. bathroom, shower room, kitchen, the utility then fit CTB fans. 80% of the moisture you produce will come from these areas. Reducing the amount of moisture that will escape to other areas of the property will result in a reduction of condensation throughout the property. Keep the kitchen and bathroom doors closed to prevent moisture escaping into the rest of the house.

If your fan is connected to your light switch, replace it with a CTB fan on a separate fused spur.

  • Cross-ventilate your home in the morning. Open windows on opposite sides of the house and open the internal doors to allow drier air to circulate. Cross ventilation should be carried out for approximately 30 minutes.

  • If possible position furniture on internal walls. External walls will be colder and therefore more prone to condensation. If you must place furniture against external walls, ensure that there is a gap between the wall and the item of furniture. You can place furniture on blocks to allow air to circulate below the item. Never overfill wardrobes as this will restrict air circulation.

Cold Surfaces in your home?

Condensation forms more easily on cold surfaces in the home, for example, external walls and uninsulated ceilings. These can be made warmer by improving the insulation levels and draught proofing. Improved insulation and draught proofing will also help to keep the whole property warmer and will cut your fuel bills. Loft insulation is relatively cheap (there may be grants available in your area) but it can significantly reduce heat loss. The eaves must not be blocked when installing loft insulation as this can result in condensation occurring in the roof space. Seek the advice of a competent surveyor if you are in any doubt.

Cavity wall insulation may be beneficial but you should always seek professional advice from a competent surveyor to assess the suitability of your property before proceeding with an installation.

The temperature of your home?

Warm air holds more moisture than cooler air which is more likely to deposit droplets of condensation around your home. Air is like a sponge; the warmer it is the more moisture it will hold. Heating one room to a high level and leaving other rooms cold makes condensation worse in the unheated rooms. It is better to have a medium to low heat throughout the house.

Keeping the heating on at low level throughout the day during cold weather will help to reduce the condensation levels but it can be expensive. Contact your energy supplier for an advice guide on how to control your system.

If you need to add extra heat to individual rooms it is better to use electric heaters, oil filled radiators or panel heaters. Do not use bottled gas heaters as they will contribute to the condensation problem.


Be careful not to over ventilate your home when it is cold, as it will cause the temperature to drop and make condensation more likely. It will also increase your energy costs. As a general guide, look outside and if you feel you could not dry your washing outside then do not open your windows for a prolonged period. The cold moisture laden external air may simply enter your property and add to the condensation problems.

I hope that the above is helpful. By making a few simple changes to our lifestyle we can significantly reduce the problems associated with condensation. If you require further advice, please feel free to get in touch. I am happy to carry out a survey and recommend the appropriate measures needed to reduce the condensation levels in your home. If you are outside of the geographical area that I cover I am more than happy to recommend a competent professional locally who will assist you.

Good luck. Neil Marsden Snr

Independent Damp & Timber Consultant

CSRT, CSSW, HNC Building Technology.

Copyright © 2017 Neil Marsden Snr

Black spot mould at eaves level in a cupboard. Cold bridging at eaves level is resulting in condensation and the growth of black spot mould.
Condensation Affects Wall finishes The client has had to throw out a number of items of clothes and shoes due to damage by mould.
Severe mould on an external wall Condensation has been occurring behind a unit placed against an external wall resulting in severe mould growth.
Furnishings damaged by mould growth. This photo shows the damage that can be caused by condensation and the resultant mould growth.
Condensation occurring on a ceiling The photo clearly shows where the insulation has not been fitted properly at eaves level.
Condensation/blackspot mould Poorly fitted loft insulation results in condensation to the ceiling.
Ceiling fan in a bathroom. Ceiling fan linked to the light switch proves to be ineffective. Replacing with a modern humidistat controlled fan will result in significant improvements to air quality.
Damp staining occurring behind a sofa. The client was shocked to find this damp staining behind their sofa. Condensation was the result.
All case studies