posted 7 months ago
Great question, Viva!
The cap is only used after the coals have burned out.
The purpose is to *stop* all air movement through the system so that the warm room air is not drawn through the system and vented out the chimney.
Traditionally, this is done with loose bricks laid over the wood feed, though that can have gaps and still slightly leak.
With The Cork, almost zero leaks occur which keeps the space even toastier!