Design Goals: The heat storage system does all the work to moderate the temperature on sunny winter days. The role of the ventilation system is simply to exchange stale air with fresh according to the needs of the plants. In the process, we want to recover as much of the heat in the air and embodied in the water vapor as possible.
Our Design: We will use a heat recovery ventilation system (HRV) running at approximately 500 CFM to ventilate our greenhouse. This was sized to handle the expected ventilation requirements of our 1000 sq. ft. greenhouse. The HRV will be turned on automatically by a humidistat. Fresh air from outside will be preheated in earthtubes.