I have the same problem too. It's still summer here in norcal so growing in my shed during the day with lights sometimes gets the temp up to 90. Its 12 ft x 4 1/2ft x 8ft tall. I am using a fan and a cool mist humidifier to get the temp down. The humidifier seems to be helping with the humidity but the temp doesn't budge much until night. Should I go for a portable ac unit or build an air intake with exhaust fan? Don't think I have the space or $$ for both unless its absolutely necessary. It seems my plants are growing very slow. (Not sure how they should look a month from seed) Any experienced growers please help