I am planning to build a grow room by sectioning off a corner of the building. The building already has insulation but it gets pretty hot in summer about 30 degrees and down to 0 degrees in winter or more. It will be about 2.4 metre square. . I am thinking of using 75mm insulation board for the walls and lining inside with dimond difusion for reflectivity .Then using an air con unit and space heater in summer/winter. Any suggestions please.