WE SET THE UNIT INTO A CORNER FIREPLACE THAT HAD A METAL LINER, THAT WAS PREVIOUSLY USED. BUT WE HAVE A OPEN DOORWAY INTO THE FOLYER AND A LONG ROOM OPEN INTO THE KITCHEN, THEREFORE, THE HEAT CONTAINED IS MIMINAL AND SHOULD BE A LARGER UNIT. I WISH THAT YOUR EXPLAINATION WOULD HAVE NOTED THAT OPEN DOORS COULD EFFECT HEAT RETAINED. BUT I DID NOT FIND A UNIT LIKE THIS ONE IN A BIGGER SIZE.