I was emailed the following pics of a Rocket Mass Heater (a superhigh efficiency homemade hybrid masonry heater) just commissioned in Co Down by off-gridder Steve Byrne
with the description from Steve "Test fired our rmh today for the first time before adding cob around the bench and barrel, and thankfully it works well. I'm amazed at how much heat it generates with so little fuel, despite having spent weeks reading about them. Now to make it pretty..."
I see also that Steve has written about this on his blog here: