Controlling moisture build-up
Moisture accumulates in the house from people bathing, showering, cooking, breathing, and watering plants.
It also comes into a home from outside.
Some appliances, such as unvented gas heating, clothes dryers, dishwashers and washing machines also produce excess moisture into the air.
The moisture builds up quickly and is worse in modern homes which are built to be almost airtight.
On cold days you can see the moisture when it collects on the windows as condensation.