Condensation and Mould Control

The Cook Group have been solving customers’ condensation and mould growth problems for over 42 years. Since 1997 we have fitted quite literally  thousands of Drimaster and Flatmaster positive input ventilation units, along with the Genie and Cyfan extract fans from the Nuaire range. The unobtrusive, economical units’ control and remove the problem of condensation at its source, dramatically improving the domestic environment. The drimaster units come with heat recovery options also.

Cook Group are the only approved installer of Nuaire and Elta products in the Hull,  East Riding and North Lincolnshire areas, and all of our surveyors and installers are fully BPEC qualified domestic ventilation installers.


What is condensation?

The amount of water (or water vapour) in the air will always vary with temperature. Basically the warmer the air is, the greater its water-holding capacity. In simple terms warmer air (i.e. when your central heating is on) holds more water vapour than colder air (i.e. on a night when the central heating is switched off)

Air within a building is usually warm and can hold a considerable quantity of water vapour without there being any problems, however when it is cooled by contact with a cold surface (such as a window or external wall) or when your heating shuts down for the night, the excess water can no longer be held in the air as a water vapour and condenses as liquid water on walls, windows or other cold surfaces.

Condensation is one of the most common forms of dampness in residential buildings. It is mainly caused by warm, moist air from household activities such as cooking, washing, bathing, or even just breathing condensing onto colder surfaces in the home such as walls, window and ceilings.

From these activities alone, each person produces an average of four pints of water vapour a day. This means a family of five will produce approximately 20 pints a day, equating to 140 pints of water vapour a week.

This figure can be much higher if you:

  1. Use unvented tumble dryers or portable gas heaters.
  2. Dry clothing indoors or on radiators.
  3. Leave windows closed when cooking or having a bath or shower.

How do I know I may have a condensation problem?


An obvious symptom is water streaming down the inside of windows, particularly bedroom windows in the morning.


Mould growing on walls and ceilings; underneath a bay window, behind the television, under a bed or behind wardrobes and furniture. This mould growth can be virtually any colour, with the most common being black, green, brown, white, yellow, orange and pink. 

An Earthy or Musty Smell

An earthy or musty smell, particularly if the house has been empty for a while.
This could be if you have been away for a weekend or even just out of the house for the day.

(We don’t want to show you a picture of that!)

Leather shoes or clothes in wardrobes smell musty or have mould on them.

Damp Patches

Damp patches appear on plaster in ‘odd’ places, particularly on outside walls. These patches appear and disappear on a regular basis.

When and where does condensation occur?

Condensation can occur at any time, but it is more likely to occur at night because the air temperature falls, which can cause humidity to rise.

As surfaces in the home become colder there is an increased likelihood of condensation forming, especially on windows or external walls.

Fortunately, there are ways of Controlling Condensation, and the Cook Group can assist you.


  1. Improved heating and insulation will help to increase surface temperatures. However, this generally does not treat the actual CAUSE of the problem and can be very costly.
  2. Close bathroom and kitchen doors when bathing and cooking and open a window in these rooms if possible
  3. Avoid the use of portable or LPG gas heaters the use of these heaters can cause massive condensation problems.
  4. Using a dehumidifier will help to control the symptoms of the problem. However, this only treats the symptoms and not the cause, they can be noisy and costly to run (up to 3 pence an hour!).
  5. Provide adequate ventilation by the means of a Nuaire Drimaster, Drimaster 2000, Drimaster 365, Flatmaster or a suitable Nuaire Cyfan range extractor fan. These types of unit can control and remove the problem before it occurs.
Condensation Control 9th January 2019