The air you breathe in your home is clean (i.e. as free from pollutants as possible). For your health and comfort, your home should have an exchange of air between the indoors and outdoors. Without the air being exchanged, your home can accumulate pollutant moisture. The exchange of stale air with fresh air will reduce the potential for problems.
Moisture is continually being released inside your home through cooking, showering, washing dishes and watering plants. A typical sign of moisture is condensation on windows in the winter months. An HRV (Heat Recovery Ventilator) or an ERV (Energy Recovery Ventilator) can help prevent this problem.
HRV & and ERV technology offers a solution for fresh air, better climate control and energy efficiency. These systems are an effective way to bring fresh air in while removing the stale air. Although a window will work, it does not filter the air that enters the house. You are also letting in air from outside that is a different temperature than the air that is in your home already and therefore using more energy to warm up or cool down that fresh air.
Your furnace fan & HRV / ERV should be left on at all times.