fmsm
Minister of Fire
Whether the hot air in your flue comes from the house or the outside , you are paying for the pellets which heat it.
If you preheat this air with a concentric flue system the stove will be a percent or so more efficient : you will burn fewer pellets.
I prefer to have an OAK to avoid cold drafts around my feet , a question of comfort , but does this matter in a basement ?
When you burn without an OAK the air is replaced from outside. This not only creates drafts but is also very inefficient.