Stove Choices

Water is at first look a sound choice in and of itself. It is much less about the density and much more about the specific heat capacity. It is cheap, readily available and is often used by some (bottles of water placed around the roots of plants/bushes/trees) etc as frost mitigation. I think some folk may want to experiment with this but be aware of the issues that come with it.

Pulling out a quote:-

"Specific heat capacity often varies with temperature, and is different for each state of matter. Liquid water has one of the highest specific heat capacities among common substances, about 4184 J⋅kg−1⋅K−1 at 20 °C; but that of ice, just below 0 °C, is only 2093 J⋅kg−1⋅K−1. The specific heat capacities of iron, granite, and hydrogen gas are about 449 J⋅kg−1⋅K−1, 790 J⋅kg−1⋅K−1, and 14300 J⋅kg−1⋅K−1, respectively.[3] While the substance is undergoing a phase transition, such as melting or boiling, its specific heat capacity is technically infinite, because the heat goes into changing its state rather than raising its temperature."

Adding other stuff into solution in your water will alter its phase transition temperature (freezing point, boiling point etc) but increasing its density does not help at all.

Water (especially with other stuff in solution) comes with its own maintenance and environmental risks. It is not really a fit and forget option for a low tech hut that is used occasionally and will be prone to some degree of freeze/thaw. I also have a big aversion to contracting legionaries disease. Warming up volumes of water to breeding temperatures for long periods of time is arguably a touch risky. You can of course mitigate this with additives and regular change etc but it is for me a lot of faf and I am on holiday in my hut LOL.

Putting all of this together and finding something fireproof to place directly around a stove (burn guard) was sort of where/how I arrived at the suggestion of granite, magnetite(Iron) or combined concrete blocks. Better still if you don't have to make them but can score enough surplus storage heater blocks. And I guess how the storage heater brick makers arrived at their own decision on materials.

There is however lots of room for experimentation here, real life applications of anything are always a compromise, there is no one size fits all, and a compromise that suits me may not suit anyone else.

BTW just thought if you had the room it may be better to build a recycled storage heater block surround by laying the blocks on their flatter sides. Sort of C shape downwards towards the floor. They would be a lot more stable that way and still have air passages between the room and the stove..

BTW I have tried a small number of bricks stacked on top of a woodburner and they do provide some useful effect in a smaller space. But their volume/capacity is not enough to be anything other than an instructive experiment realy.

Agreed.

They are the right material but entirely the wrong shape. As they are mostly flat or tall flat and C shaped (vertically). At least when compared to a standard brick.

On shape the best shape I can think of would be like 3 doughnuts blended together endways approximating the length of a brick and as thick as a brick, give or take a bit.

The narrower sections hopefully would facilitate cutting/snapping using the usual brick cutting techniques. But the holes would be of a size to fit a standard rebar size to pin the stack. ie stack up 3 courses or so and slip full height rebar pins in the holes then thread the rest of the blocks onto the pins until they are hidden. I guess it would be possible to get a friendly blacksmith to thump knobs on top of the pins for decorative purposes and leave them showing though, But you would need to put the pins in last then.

The shape of your stack, tubular, square, C shaped etc is entirely governed by the shape of your stove and how many sides you can build around.

About the only way I could think of to repurpose storage heater bricks is to smash them up with a lump hammer or similar and recast them into a more useful block like the above with standard cement. and maybe some sand. Standard cement/concrete types are temperature compatible they are just not good enough thermally. If casting thermal storage blocks like this from scratch my reading suggest that a magnetite/sand/cement concrete mix should do the job. Or maybe as a poor second granite (grano to dust from a builders merchant) sand and cement, if magnetite is not readily available (other than smashing up and repurposing storage heater bricks).

It is a lot of effort to go to though, and maybe standard perforated bricks although a poor match thermally would be good enough. folk would have to try it out and see what worked best for them.

I tend to use my hut most in the warmer months and cook on a fire outside. I would like a wood stove but cost and indecision have stopped me! I like the idea of using electric storage heater bricks if there was an easy and tidy way of doing it

Nice I wasn't aware of Windy Smith, I am not hung up on a cast iron stove so their steel plate stoves are perfectly doable for me. The price looks reasonable too. I see what you mean about the window, although I am less troubled by that, but take the point about the light being welcome. Their oven type units are pretty interesting. Nice find there.

I had initially looked at the Salamander stoves and in particular the Hobbit Stove, but they are very pricey.

https://salamanderstoves.com/product/the-hobbit-stove/

I have mused and read up a bit on stoves, and want something that features some degree of mass heating. To slow down the boom bust heating effect of a low thermal mass hut. I also want to make sure that whilst visitors and ourselves are maneuvering in a small space that we can avoid leaving too much flesh/clothing welded to the hot surfaces.

On cooking with a stove for most stuff a hot top is plenty enough (combined with something like a cast iron casserole or dutch oven, plus coffee pot etc) But the idea of actually having a built in oven as well definitely does appeal. I am a bit undecided on this one as the whole back to basics thing is part of the hutting interest for me.

On mass heating, stacked loose perforated brick surrounds pined with rebar through the perforations is an option and gives a lot of flexibility. Although bricks whilst they can look good are not great thermally. But recycled electric storage heater bricks would be an option, if there was a sensible way to make them look good and pin the stack for stability. I think I might like to avoid mortaring up a brick surround as it restricts the airflow around the stove and is a bit immutable when we might need to do stove maintenance. Bricks of whatever sort and build are definitely good though for protecting the wooden walls of a hut.

I think something that will do small volume fast burn and can be self feeding to some degree would be advantageous, But we are well out of the windowed stove territory there. Rocket stoves come to mind for this.

I've not got a stove in my hut yet but I'm always drawn to the Windy Smithy stoves for reasonable price and they also seem popular for small spaces. The only drawback with them is no glass front as the extra light from a wood burner would be very welcome in a hut.