Ventilation systems work in conjunction with your heating and cooling systems. You can simply open windows which is fine when the outside air temperature is moderate but if the difference is more than 10 degrees different from your inside temperature much of the time in winter and summer, then opening windows will waste a lot of heating or cooling. Heating or cooling loss also occurs through leakage in cracks and under doors.
In heating or cooling climates, you can expect about one third of your heating or cooling to be lost through open windows, so clearly there is a great opportunity to save operating costs.
Heat Recovery (HRV) or Energy Recovery (ERV) Ventilation systems recover up to 94% and of your heating or cooling from the outgoing stale air and transfer it to the incoming fresh air. ERV systems also dehumidify so are a better solution in northern humid climates.
These systems are very important in highly efficient, air tight homes to reduce carbon dioxide and humidity build up from household activity. A good supply of fresh air improves alertness and makes a healthier, fresher indoor environment.