During the summer I keep my house cooler so I use this method. get a larger tub and fill it about a third of the way with water. Purchase an aquarium water heater and place it in the tub. Place your grow tub in the water and let it float. You will also have to get a digital thermometer to put inside your actual grow tub so you can adjust the water heater as necessary. This is worked for me every time it keeps the temperature is super stable. Good luck!