I looked on the Home Depot website and the cheapest (R13) mineral/rock wool insulation is about $47 for the standard size, which seems to be 15x47in. (I suppose

I looked on the Home Depot website and the cheapest (R13) mineral/rock wool insulation is about $47 for the standard size, which seems to be 15x47in. (I suppose 15in is close to the mentioned 27cm.) The calculator there suggests I can get about 30ft by 10ft for $650. I suppose that could insulate a single small room, but an entire building's roof? And yea this is w/o any labor and tool cost.