water droplets on the interior of a house window

Can excess humidity cause mold growth in my home?

Humidity enters our homes in a variety of ways, we take a hot shower, boil water for pasta, snow on our boots, kids leave their wet towels on the floor, and naturally through our windows, doors and basement or lowest levels.

Moisture can cause problems within the home including mold growth on a variety of building materials and contents within the home. Managing the moisture in the home is key to preventing significant mold growth within the home. 


What is humidity?

Humidity is the concentration of water vapor in the air. Humid air is less dense than dry air because a molecule of water is smaller than a molecule of nitrogen or oxygen. Naturally, dense substances will sink while those that are not will rise. Have you ever noticed that the air on hot days is warmer and stickier in the upper levels of your home? That is because the humid air is less dense and rises above the dry air.

How does humidity move through my home?

A significant amount of moisture enters the home in the basement or lowest level of the home. Air flows from high-pressure areas to low-pressure areas and is called an air current. Since temperature and humidity move together through the home, parcels of warm air and moisture move upward in through the home and will try to escape through the easiest way possible; cracks, openings, gaps in the structure or an easy exit through a ridge vent. When ventilation is compromised in the home, the moisture can cause condensation on building materials and cause significant mold growth on organic materials. 

Signs of excess moisture in the home can include: 
  • Rusty or dripping nails in the attic space;
  • Front on the roof sheathing in the attic space;
  • Condensation on the windows in the living space;
  • Condensation on cold water pipes in the basement;
  • Condensation on toilets.

What can I do to control the moisture to prevent mold growth? 

Many homes have ventilation in the roof system that promotes air and moisture flow, some newer homes have air exchangers to accomplish this. Each home is unique and the system that will remove excess moisture is also unique. We always recommend the use some sort of dehumidifier to remove excess moisture in the basement or crawl space where the relative humidity should be kept below 55%.


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