Good indoor air quality starts with a good ventilation system. Most homes are locked up tight resulting in a lack of fresh air, and during the winter months it is not alway practical to fling open windows. In this article, Six Steps to Success with Heat-Recovery Ventilation, they talk about Heat-recovery ventilators (HRVs) and energy-recovery ventilators (ERVs) and how they remove stale air from the home and replace it (in winter) with preheated fresh air from outside. Another great reason for a good ventilation system is the health benefits, which filters outside air and then distributes fresh clean air. A win-win in the cold months of winter.