Passive solar buildings are designed to take advantage of the sun's energy to heat and cool the home. This can be a very efficient way to heat a home in the winter, but it can also lead to problems with moisture. When the sun shines on the building, it warms the air inside the home. This warm air can hold more moisture than cold air. If the moisture level in the air gets too high, it can condense on the walls and ceilings of the home. This can lead to mold and mildew growth, which can damage the home and cause health problems for the occupants. There are a number of things that can be done to control moisture levels in passive solar buildings. These include: * **Installing a ventilation system.** A ventilation system can help to remove moisture from the air inside the home. This can be done through natural ventilation, such as opening windows and doors, or through mechanical ventilation, such as using a fan or an air conditioner. * **Using a dehumidifier.** A dehumidifier can help to remove moisture from the air inside the home. This can be a good option for homes that are located in humid climates. * **Sealing air leaks.** Air leaks can allow moisture to enter the home. Sealing these leaks can help to reduce the amount of moisture in the air. It is important to monitor the moisture levels in your passive solar building and to take steps to control them if they get too high. By controlling the moisture levels, you can help to prevent mold and mildew growth and keep your home healthy and comfortable. **How much moisture is OK in walls?** The ideal moisture content for walls is between 4% and 6%. If the moisture content gets too high, it can lead to mold and mildew growth. If the moisture content gets too low, it can cause the walls to crack. You can measure the moisture content of your walls using a moisture meter. Moisture meters are available at most hardware stores. If you find that the moisture content of your walls is too high, you can take steps to reduce it. These steps include: * **Installing a ventilation system.** * **Using a dehumidifier.** * **Sealing air leaks.** By following these tips, you can help to control moisture levels in your passive solar building and keep your home healthy and comfortable.