 Here's another one that can contribute if you've got a basement. If your gutter downspouts are draining within 10 feet of your home and you're in an area that gets a significant amount of rain, we're not talking Death Valley here, we're not talking rainforest either on the other side of that coin, but if you get significant rainfall, that water that's coming down and dropping all of the square footage of the water that's hitting that roof, dropping it right next to the foundation, that will contribute to your indoor humidity.