Depending on how a house is used it can be dry or wet - cooking styles, managing laundry, number of people, plants, pets, hobbies, cleaning, firewood, bathing/showers, running ventilation equipment can all add moisture to the indoor areas of the house.

These inside sources create vapourized moisture from sources including:

• Occupants: four people add about 5 litres/day
• Activities such as washing, cleaning and cooking can add another 4-5 litres/day
• Plants and pets contribute 4-5 litres/day
• Use of humidifiers
• Dryer exhaust duct (ensure proper sealing and operation of vents)

In fact, Our houses receive about 30 liters of water per day, depending on lifestyle and the number of people in the home:

While moisture can come from unsealed basements, through leaks it also from occupants through their daily living. Perspiration, breathing, bathing, washing, etc.

The more people, the more moisture. The more cooking, the more moisture. You can see that it can add up to a lot of water each day. This water needs to be flushed out of the house, otherwise things get "wet" or damp which can lead to mould and/or rot. Managing moisture in buildings is very important - if there is a lot of moisture in our houses we have to figure out how we can get some of it out. That is where ventilation comes into play.