If a bathroom you never use begins to smell, you likely have a dried out P Trap. This little loop isn't just intended to catch a wedding ring that falls into the drain. A P Trap is designed to hold water and prevent sewer gases from moving back into your habitable space. Run your facet for a few minutes and the smell will disappear.

Your home AC removes moisture from the air as it cools your home. When warm, humid air rises, it can get trapped upstairs in a two story home and cause musty smells as well as a breeding ground for mold. To maintain proper temperature and humidity levels throughout, set your upstairs thermostat two degrees cooler than downstairs.

Most people use their bathroom exhaust fan for all the wrong reasons. This tool is present to help remove moisture from your bathroom. If you don't find it exhausting to the exterior of your home, check your attic. You do not want to increase moisture in this space. If it terminates there, you should have it fixed immediately.