Getting ready to install an Englander 30 in my living room and am a little confused when it comes to my rear clearances to combustibles. I plan on making my wall protection out of 1/2" Durock mounted on the back wall with ceramic tile covering it. There will be a 1" air gap between the Durock and the drywall behind it. The diagram in the manual regarding the minimum clearance behind the stove is a bit confusing to me. What is the minimum distance i can have this stove from my wall protection? I will be using double wall stove pipe to connect the stove to the ceiling support box.