When you want to use a dual room system for your indoor growing or put your OptiClimate unit outside the growing room, you can use an OptiClimate Plenumbox. This handy gadget, an insulated case, can be installed to the back of the air conditioning unit. By using the plenum box in a dual room system there is a three-way-valve so that a single OptiClimate unit can be used. If you need two rooms to be cooled at the same time the Plenumbox is the tool to do it. Each room, usually a day room and a night room, can be checked simultaneously, the three-way-valve and additional temperature sensor carrying out this function. Connected air hoses suck out the warm air to adjust the temperature appropriately for the spaces and give you added security in knowing your plants have high quality climate control.