The Varii Speed fan speed controller is an excellent device designed to give you full control over the extraction rates of your grow space. This is the perfect solution for if you are experiencing cooler temperatures in your grow room especially during the night period. The addition of a heater to your grow space will help to increase night time temperatures but it is pointless if you are extracting that heat as quickly as it is being produced. Lowering the extraction rates of your grow room will help to preserve this heat, giving your plants a comfortable nights rest as well as saving you money on heating! You can also use a fan speed controller in conjunction with air cooled reflectors. This way you can dictate your grow room temperatures without altering the air exchange rate of your room. Fan speed controllers are often expensive pieces of kit but the Varii Speed is a cheap and effective piece of kit.