Any kiwis installed a rmh with building consent

Hi guys almost got my 4 inch batch box bath heater set up pics to come. Now I've seen this little beauty running I'm keen to install a 6 inch in the house anyone gone through council approval in new Zealand. Any advice welcome I just can't see why anyone would ever install a stupid metal box and waste soo much wood for nought.

Cheers Russ the kiwi nutter

That's the temporary bath set up simple j tube straight flame on cast iron. Batch box will be brick ducts from brick bell bath over ducts