Hi, I am new to the forum, so hello! I am from the UK but live in Latvia. I have looked at Rocket stoves in the past but now I want to build one to heat a workshop, so I am looking for plans for a no metal mass heater. The room is 6.5 meters by 5.1 by 2.5 high or 21 foot by 17 by 8 high. Not well insulated but not drafty. I was set on buying some lightweight insulation bricks today to build the heat riser and was winging a design but was luckily sent to a specialist ceramic dealer, who quite blew my mind with all the possible materials I could use plus some pallets of used fire bricks of many different types including clean though pitted lightweight insulating at 50 cents each. So I would like advice on the best way to go and what design, though I favour the bell types at present. There are cast-able materials etc! Strangely for me his buildings were heated by the air conditioning units and it seems more economic than our present electric use plus we have a wood fired heating system on top!