We have now learned how to build energy efficient buildings so tight that virtually all air leaks are eliminated. GREAT – but an unwanted side effect is the constant recirculation of stale air containing the build-up of pollutants, odors, carbon dioxide and excessive moisture. Letting in fresh air through an open window carries it’s own set of problems, not the least of which is the need to heat this cold air in winter and cool it in summer. The solution – a heat recovery ventilator (HRV) which uses exiting conditioned air to preheat incoming air through a heat exchanger. An ERV, one step further, also maintains a good indoor humidity level by exchanging humidity as well to maintain a healthy indoor environment. This humidity exchange also pre-cools incoming summer air. ERV’s mean cleaner, fresher, healthier indoor air.