Managing Moisture in Passive Houses
How Much Moisture is OK in Walls?
Passive houses are highly energy-efficient buildings that rely on airtight construction and passive solar heat gain to maintain comfortable indoor temperatures. However, this airtightness can lead to moisture problems if not properly managed. Moisture can accumulate in walls from various sources, including indoor activities like cooking and bathing, as well as from outside sources like rain and snow.
The amount of moisture that is acceptable in walls depends on several factors, including the climate, the type of construction, and the materials used. In general, it is recommended that the moisture content of walls does not exceed 15%. Higher moisture levels can lead to mold growth, structural damage, and decreased energy efficiency.
How to Control Moisture in Passive Houses
There are several things that can be done to control moisture in passive houses, including:
- Ventilation: Properly ventilating the house is essential for removing excess moisture. Use exhaust fans in kitchens, bathrooms, and other moisture-prone areas. Consider installing a whole-house ventilation system to circulate fresh air throughout the house.
- Air Sealing: Air sealing is another critical measure for controlling moisture. Seal all cracks and gaps in the building envelope, including around windows, doors, and pipes. This will prevent moisture-laden air from entering the walls.
- Vapor Barrier: A vapor barrier is a material that prevents moisture from passing through it. Install a vapor barrier on the warm side of the walls to prevent moisture from migrating from the interior to the exterior.
- Moisture-Resistant Materials: Use moisture-resistant materials for walls, such as cement board, fiberglass-reinforced drywall, or closed-cell spray foam. These materials are less likely to absorb and retain moisture.
- Regular Monitoring: Regularly monitor the moisture content of walls using a moisture meter. This will help you identify any areas of concern and take appropriate action.
Conclusion
Managing moisture in passive houses is essential for maintaining indoor air quality, preventing structural damage, and maximizing energy efficiency. By following the tips outlined above, homeowners can effectively control moisture levels and ensure the long-term health of their passive homes.