2 10 x 12's. If we get really cold I have 2 Oil heaters ( electric) that I can add. The fans from the milk house heater's circulate the air. I keep one house min. temp of 55º and the other 50º. I may have to upgrade that next winter. We are planning on renovating one greenhouse to make it taller so I have more sidewall area. Was supposed to do that this year but a complete bathroom in the house got in the way.
