Airtight construction saves energy and improves the durability of buildings. While a home can never be “too tight”, it is necessary to provide automatic ventilation in all homes that have been air sealed below 4 Air Changes per Hour (ACH). This ventilation helps to control the flow of water vapor and maintains superior air quality for the health of the occupants. To reduce energy loss in zero energy homes, heat from the ventilated air can be captured rather than wasted by installing heat recovery ventilators (HRVs) or energy recovery ventilators (ERVs). These ventilators bring fresh air into a home and discharge stale air, while retaining about 70% to 90% of the heat from the discharged air and returning it to the incoming air. In addition, HRVs and ERVs each help manage moisture in the air in different ways. Learn more about HRVs and ERVs from Green Building Advisor.