Air infiltration in greenhouses

Air infiltration rates are important in determining greenhouse heating requirements. Design recommendations usually suggest one to two complete air exchanges per hour under calm conditions. Tests made in 10 commercial ranges showed no greenhouse in excess of one exchange per hour, with one as low as 0.34 per hour, and an average of 0.56. However, additional tests at CSU showed marked variation, depending upon greenhouse size and heating methods, as well as type of structure and outside wind velocity.