Just finished a project on our wood heater which improves the function quite a lot by eliminating the consumption of the air in the house and simply heating the volume of air captive indoors.
The change made was to drill a hole through the wall of the house to the outside also drill a hole through the rear of the wood heater then a pipe was inserted through the wall and into the heater.
Beforehand a simple butterfly valve was built into the pipe in order to control the air flow.
The first test worked perfectly except that the diameter of the pipe was too large(60mm) and 30/40mm would do and even though the butterfly valve was a good fit it was not blocking enough air (since corrected).
Now instead of sucking house air into the heater and up the flue,to be replaced by cold exterior air from windows and door cracks ,now the hose air remains within the house and simply gets warmer and warmer.
