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Refractory lining the wood stove

Super insulated burn unit

We have begun lining the inside of the wood stove with heat proof insulating materials. The first thing to do was get a good amount of insulation down for the stove floor. For this we used some insulating fire brick type material that came from Dave’s chimney reconstruction. It was a little oddly shaped, so it ended up being a procedure much like stone wall building, using standard fire cement to hold it together.

Then, we popped in some some super C26 graded insulating fire bricks. These are very lightweight – being mostly little air bubbles – but very heat resistant. They are also a tad soft, which makes them easy to shape with a handsaw, but means they need to be covered with something more durable….

We used a product called mouldable firebrick. It is very heat resistant but also durable and dense. Application is interesting: you pick up clumps of it, put it in place then use a mallet to sort of hammer it into shape and position. Here’s the stove from above. The aim with all this is to get a super insulated burn unit, which will provide favourable conditions for excellent primary and secondary combustion (For lots more info on the design of the stove see here).

If you remember, the idea is that the wood will burn sideways, from left to right in the photos. The next photo you can see the channelling arrangement.

The two pipes running down the cylinder take primary and secondary air. They run all the way down the insulated burn unit so should be able to pre-heat the air nicely.

The flue inside the burn unit finishes just before reaching the top, so that the superheated combusting gasses will hit the hotplate before travelling up and on to the heat exchanger.


Around this ‘internal flue’ we packed vermiculite insulation. Then we used some spare sheet metal (this stuff’s from an old microwave I think) just to keep everything in place. Notice we have also tack welded on a ring round the inside where the hotplate ‘lid’ will fit, so that we can sandwich some fire rope seal in there.

So that’s it for now – burn unit pretty much complete, next stop, heat exchanger…

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