While it's true that a plant will tolerate higher heat with the addition of CO2, it will still be able to grow, you need first a sealed room. Plus the expence of a good controller and tanks, etc....but when all is said and done you still have a heat problem.

Hey randomking,

Not sure what you consider an air cooler, but I am familiar with AC and with chillers.

A chiller system usually consists of a water to air heat exchanger, a resivior and a aquarium chiller (small compressor to cool water). Where low humidity is a problem you can keep the rez in the room you are cooling, leave the top off and evaporation from the rez increases humidity. The chiller needs to be outside the room.

Google Hydro Innovations, they make water to air exchangers (called IceBox) that are cold water devices, that done properly and with enough chiller capacity can serve in place of an AC system. They also make some great insulation pkgs to cover light hoods that cuts down on the radiant heat given off the lights.

As for AC systems one of the most energy efficent units is a small split system like Mitsubishi makes. These consist of a compressor/condenser coil that needs to be outside, or in a cool ventable area and an inside unit with coil and fan. These are efficent due to thier excellent rotary compressors. The least efficent is usually windowless units but these have the advantage of need only a 6" hole or so to vent hot air out of the room.

While 25% humidity is low it would be preferable during the end of flower then say 50%.
Also keep in mind that if you have a bunch of plants in there humidity will go up also especially during lights out.

Would need more info to figure sizing of chiller or AC.

OM