Humidity is a big deal when it comes to a healthy indoor environment. Seasonal changes in humidity can be the cause of high or low indoor humidity levels.
When indoor humidity is high, you can end up with health problems related to respiratory infections, asthma and allergies, and the house can have mold growth problems that can even lead to structural damage. When indoor humidity is low, you can end up with a different set of health problems related to increased exposure to bacteria and viruses. The structure of a house doesn’t suffer much from low humidity levels, but wood floors and other natural materials can shrink and crack as they dry out. Obviously, neither situation is ideal.