As a rule of thumb, an air conditioner needs 20 Btu for each square foot of living space. Some would suggest up to 30 btu per square foot. 225sqft x 20bth = 4,500btu/h. Also you need to add 4,000 btu/h for each 1,000 watt hps. So for veg you have 4 lamps equalling 16,000btu/h plus 4,500btu/h =...