David wrote:
As for the floor, it's currently stone
flags laid on ash and earth. They're coming up for re-use elsewhere
and then it's a DPM, screed and several weeks later, wooden flooring
laid on battens. It's just struck me that a vent into the underfloor
space from outside and then a vent under the woodburner would
ventilate this underfloor quite effectively. Thence to Lidl for the
hygrometers... Thanks again.


Bear with me a second. If your final floor is over a pretty sealed up
space with only wood between the room and it, the very last thing you
want to do is ventilate it to the outside. It will get amazingly cold.
By all means have some vents to the room if you must, but not to the
outside.


Put some form of pipe in the ground under the screed, and exit it up
higher than damp somewhere outide, with and upside down U bend to stop
rain getting in, amnd something to stop insects and rodents getting in
as well, and take that direct to the fire area before you do all the
screeding. Oh and if thats what you are doing. put at least 50mm
extruded polystrene or Celotex into the screed for insulation.