Hi everyone,

I am new to posting at this forum, but I have used it often to get ideas for the greenhouse I am building.

I am starting to construct a 16x20 greenhouse out of cedar with corrugated single layer polycarbonate for the covering. My reason for building this house is different than most in that the main thing I am trying to do is get more heat and higher night-time temperatures in the spring and summer to grow tomatoes. I live on the Oregon coast where the summer daytime temps are in the 60's and 70's. At night temps are 40's to 50's. This is not ideal for tomatoes or other heat loving plants.

I would like to know how much exhaust ventilation to plan for. The cfm number I get is around 5000. To get this much turnover will require a 24" fan with a couple of 20" vents. In this cool climate will this be necessary? Also do I only want to run it when the temperature gets over 80 deg. or so, and the rest of the time rely on open vents and natural air flow? I also plan on using shade cloth so this should help. In addition to the low vents and exhaust fan at the opposite gable end would it be beneficial to frame in some opening windows?

Thanks,

Andrew2