Condensation is a complex subject
Condensation has become the single biggest factor in modern living and life style and the impact of Condensation on people’s lives is increasing almost daily. In principal Condensation is the result of a lack of control of a living environment and since most of us want to live their lives in a cozy ‘sealed up’ box, it has to be understood that the more bodies contained in a living environment, the more moisture will be generated. On average, human beings exude at least 2 pints of moisture vapor per day and in conjunction with other demands of modern living and life style, extreme cases of up to 12 pints can be generated on a daily basis. There is a limit to how much moisture vapor can be held in the atmosphere of any ‘sealed up’ living environment and a key ingredient is temperature. The warmer the environment, the more the living environment can hold as moisture and therefore by contrast, the cooler the environment the less moisture that the environment can hold as moisture vapor. Once the level of moisture vapor in conjunction with the temperature reaches saturation point, moisture vapor becomes water droplets and this is when the trouble starts. The water droplets will be attracted to colder surfaces (windows and exterior walls which have a tendency to be colder than other surfaces of the room) and to poorly ventilated areas such as behind items of furniture, behind curtains and piles of personal possessions stacked against any wall.
The water droplets have been derived by a process called ‘deliquescence’ and if the water droplets are left where they fall, they are the only predicament and source of unsightly black/grey stains on interior surfaces. There could well be an underlying damp problem which may have exacerbated the problem and which may have created a colder surface than might be normal. However, one can be sure that anything black/grey is caused by impact of Condensation which is a very different issue to Rising, Hygroscopic or Penetrating Damp. For example, the reason why leather goes moldy in a humid environment is because leather attracts moisture and breathes and that is why we wear leather shoes on our feet!