We have recently bought a house and are in the process of opening up the old fireplace. We have taken it back to the builders opening and are looking at putting in one of the open fires that burn with 'super efficiency' (the tortoise by firebox/flamewave fires). However, having looked into it firther we will need to put in an air vent and it is here that we are lost. It will need to be 160 sq cm - what do I need to do?? Is it a job we can take on ourselves or should I ask a builder to come and do it for us? The walls are brick with a stone outer and are fully insulated. Also, are we supposed to have involved a building inspector? So far all we have done is open up the fireplace - how much will he charge and what will he want to see?? 
