The Tamarack HV1600 has all of the energy efficient features of the HV1000 in a more powerful two speed model with remote control. The lower, quieter speed is 1150 CFM’s and the more audible, powerful high speed is 1600 CFM’s. The physical size is the same as the HV 1000. Just like the HV 1000, the HV1600 has R38 insulated doors that remain closed until the fan is in use, and then open to allow the heat of the home to enter into the attic and exit through the preexisting attic vents. If there is a minimum of 3 square feet of attic venting, there is no need to cut additional holes in your roof.