Moisture is responsible for many serious problems and damage in walls, floors and attics, and for higher energy bills and health hazards.
Excess moisture also increases energy consumption. Your heating and cooling system will have to work harder and to use more energy to deal with moisture.
Indoor sources of moisture
There are various mechanisms through which liquid water, humid air and water vapor can penetrate the walls, attics, roofs and floors.
But indoor sources of moisture are also relevant.
Horror Stories About Moisture in Airtight Homes
That's common to hear horror stories about damages caused by moisture trapped inside walls and ceilings. And some of the stories are often wrongly associated with airtightness, in modern energy-efficient homes.
Drainage Systems: The First Line of Defense Against Excess Moisture
A well designed drainage system is a very effective way of directing rainwater away from the foundation, and one of the most effective means of preventing moisture in basements and crawlspaces.
Anyway, surface drainage is seldom sufficient in rainy climates; under-ground drainage systems are also critical.
Wall Moisture Problems Can't Be Solved With Ventilation
Walls should be kept dry, which isn’t easy to achieve.
There are various mechanisms through which humid air, rain and snow water and water vapor can penetrate the exterior walls.
See: Wall Moisture
Many Serious Moisture Problems Come From Crawlspaces and Basements
Many brand new homes have foundation moisture problems.
Attic Moisture May Come From Indoors or Outdoors
Attics are prone to moisture issues, often associated to roof leaks.
Inadequate levels of attic ventilation, ill-designed attic venting systems and leaks in the attic floor can also be a cause of moisture.
Ventilation Can Solve Small Moisture Problems; But Just That
Air circulation is a way of controlling mould and condensation in closets, or in unused rooms.
Anyway, most moisture problems have to be solved by acting at roof leaks, plumbing leaks, cracks and holes in walls or problems with the foundation drainage and excess indoor moisture.
Moisture Damages and Health Hazards
Wet homes are not durable or healthy.
Excess moisture is not just a cause of odors and damages in walls, attics and floors. Excess moisture is also a cause of mold and mildew, fungus and contaminants, responsible for health problems such as asthma or allergies.
Controlling moisture levels should be a priority.
Exhaust Ventilation for Indoor Moisture Removal
Cooking, showering, clothes washing and dishwashing are important sources of indoor moisture that must be properly addressed.
Every home should have exhaust fans in the kitchen and in each bathroom, ducted to the outdoors.
Moisture in Windows
Condensation on windows occurs when moist air comes into contact with the cool surfaces of the glass; windows are often the coldest surfaces in the house. But this doesn't mean that the windows are at the source of the problem.
Moisture & Windows
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House-Energy Video on Moisture Issues: