There is  always some moisture  in the air  even if you cannot  see it. 
  Everyday activities add extra moisture to the air inside your home. You may notice that there is condensation on your windows first thing in the morning, this is because one person breathing adds half a pint of moisture to the air over night.
Everyday activities add extra moisture to the air inside your home. You may notice that there is condensation on your windows first thing in the morning, this is because one person breathing adds half a pint of moisture to the air over night. 
 Condensation  occurs when  warm moist  air  hits cold surfaces .   
 This moist air condenses    and forms water    on cool surfaces such as walls, mirrors,   wall tiles and windows, and even some clothes.   
  When the moist air is warm it rises and often ends up on ceilings and in upstairs rooms and then forms    patches of black    mould.    This may not be in  the same room  that the  moisture has  come from.    
   Condensation is not caused by water penetrating from outside of your home, it is caused by moisture which is produced from inside the home.     
 Here are some examples of how much moisture we produce in the home:   
| Drying clothes indoors = 9 pints   |    |  Cooking and using a kettle = 6 pints    |     | 
|  Breathing (2 people at home for 16 hours) = 3 pints      |     |  Taking a bath or shower = 2 pints     |     | 
|  2  people  active for 1 day =  4 pints    |     |  Four people sleeping  =  3 pints      |     |