Higher temperature> less unburned gas> less pollution
Received idea! The temperature is linked to the combustion of wood and even the type of wood, its residual humidity, etc.
a wood whether open or closed hearth will not provide more or less than what it allows to provide calorically.
However in a closed hearth, most of these calories remain inside, enclosed as in a closed box and the heat comes out through its best exit door, the pipe, like water through a tap. The rest is evacuated partly by conductive materials such as cast iron (not the best for that matter), and by the glass and even if it is clean.
Closed hearth less risk of fire.
In the event of a chimney fire, the fire is fanned in an open hearth,
the chimney fires are due to the soot accumulated in the conduits and there is a risk only if the conduits have not been swept, which is necessary and compulsory in a closed hearth too. So neither worse nor better.
whereas in a closed hearth, with the door closed, it suffices to reduce the air intake and the fire stops itself.
and in an open hearth, you just have to drown the hearth with water, quite simply. (chimney fires don't happen every day!) It obviously does not have the same advantage as a simple cut in air supply.
So each type has its advantages and disadvantages obviously, so it's a question of choosing between more heat inward or more heat outward and with equal consumption, the heat is less inside or else you have to burn more wood and therefore pollute more too.
With insulated stainless steel tubing or included in a plug, respecting the safety distances (DTU 24.1 and 2), the risk is practically non-existent
the casing does not prevent the accumulation of soot in it, it simply reduces direct thermal shock with the outside and currently insurance increasingly refuse to ensure if the conduits are not cased. So the casing argument is no longer one.
"We make science with facts, like making a house with stones: but an accumulation of facts is no more a science than a pile of stones is a house" Henri Poincaré