Have you heard of "Sick House Syndrome?" Homes that don't have adequate ventilation can't "breathe," and their air quality decreases. Indoor pollutants and moisture build-up can cause problems, especially for young children, elderly residents, and people with some kinds of chronic illness.
Read on for more information, including some basic tips for addressing Sick House Syndrome: http://rismedia.com/2014-06-21/what-is-sick-house-syndrome-and-what-causes-it/