Bread oven/rocket stove/masonry stove construction workshop?

PLEASE NOTE THIS POST WAS A PRELIMINARY ENQUIRY ABOUT WORKSHOP INTEREST BACK IN 2010 AND CONSTRUCTION PLANS SUBSEQUENTLY CHANGED (see Comments section below)

This post is a preliminary enquiry to see if there is likely to be enough local interest to make it worthwhile planning and running this construction as a series of workshops. The construction will be going ahead anyway. (If you’re interested, please leave a comment below rather than responding on eg. Facebook. Comments on this page won’t get lost or superceded by more recent news.)

I’ve looked at several options for our cooking and winter space heating, but all have ultimately been filtered through a single criterion: efficiency. Most conventional woodburning stoves are not very efficient. A compromise has to be reached between combustion efficiency and comfort since so much of the heat generated is immediately radiated from the appliance. Efficient combustion = a room too hot for comfort. Conversely, a comfortable ambient temperature = inefficient combustion. That inefficiency has a number of downstream consequences; a large annual firewood requirement, creosote and tar build-up from incomplete combustion, increased frequency of cleaning, fire risk, etc.

A big AGA-type cast iron woodburning range with a back boiler is a wonderful thing to be sure (I grew up with one), but it’s a bit like one of those all-in-one printer/copier/fax machines: does all of those jobs, but none of them particularly brilliantly. It takes several hours to bring up to running temperature. Heat your water for a bath and you can’t bake at the same time (forget about running radiators – they really don’t work too well). Cook too many things on the top of the stove and the roast potatoes go soggy. If you’ve got good dry hardwood, it is possible to stoke the fire well enough to do all 3 but you’re down to your underwear and sweating into the frying pan. And in summer, a cooker like this is far too hot to use in comfort, so some alternative is needed.

Having gotten on a roll with the KISS principle in the renovation of the building, I started questioning the convenience of the single heat source and wondering whether it had eclipsed a more balanced assessment of the total energy input involved. Firewood takes a lot of effort to fell and chop (or alternatively a lot of money to pay someone else to do the felling and chopping). If we could halve our annual firewood requirement by lighting a fire only when required, maximising its efficiency both in terms of heat production and delivery for the purpose required and by storing surplus heat for later release, it ought to far outweigh the inconvenience of having to light and tend more than one fire.

Just as importantly, burning efficiently means minimal build-up of toxic deposits and virtually no greenhouse gas emissions.

So I have a cunning plan. We are going to remove a section of the upstairs wall between the two rooms and rebuild it as the core of a masonry heater, fed by a firebox in the living room. The use of the wall itself to store heat from the stove means that we need only burn one stove-load of firewood at maximum efficiency every 12 hours to keep a constant comfortable heat in the two upstairs rooms.

Below it, in the kitchen, a rocket stove will serve as our cookstove. With much greater efficiency in delivery, a rocket stove takes far less time to bring to running temperature than a cast-iron range and does not store heat so can be used year round for cooking. It has the additional advantage that it runs on much smaller pieces of wood, so harvesting the wood to run it can be less labour-intensive (it can even be done easily enough by hand rather than using a chainsaw). Last, but far from least, a rocket stove can be built for a (very) small fraction of the price of a cast iron range cooker.

A separate (possibly also rocket) baking oven will be built on the exterior of the building. Both rocket stove and bread oven will vent into an external chimney above the oven which, in winter, can be diverted via dampers into the masonry matrix upstairs before returning to the chimney.

I’m also considering running pipework for winter domestic hot water through some part of the system at the same time.

So. Question. How interested would you be in attending a series of workshops based around the construction of this integrated cooking/heating complex? The way I’m thinking right now is that we will have separate workshops based around each component of the system – the masonry stove, the bread oven and the rocket stove – with the option to attend any or all. The response I get to this post will determine whether or not we do this.