The bit I was referring to though are just random gaps, think the last owner got someone in to do the insulation in the attic and they just lobbed it about randomly from how it looks up there
It's usually considered as a trickle heating system to stop the tank and pipes from freezing up. I'm planning on boxing mine in and insulating around it.
Don't forget if you have a gravity fed system you should really not insulate under the tank.