Saturday, 27 October 2007

Hearth insulation

And now for the insulation. I'd decided to use Thermalite insulating blocks to give 4" of insulation under the firebrick hearth. I figured this would be a lot easier than pouring vermiculite or perlite concrete, and it was. It took about an half an hour to cut the blocks to rough shape (you can cut them with a handsaw, a bit like sawing up tough polystyrene foam), then about an hour to mortar them all in.
About as easy as it gets, and cheap - this lot cost me £12. You can see a couple of thermocouple wires here - there's already one mortared under the insulation, as I want to see how much heat gets through these things. The one arched across the top will go inside the centre firebrick in the hearth. There'll be others in the dome, in the oven space, and in the outer wall to see how much precious heat I'm losing.
The blocks suck up water like a sponge, so I'll need to get a cover over this pretty soon. Next comes the fun part - building the oven.


Tony said...

Do you build in a frostfree region or might you have to wait until Spring for the bulk of the build?

My wife is keen to get on but I'm not sure about how well things will cure. On the other hand, maybe I should stop prevaricating and pursue fire bricks more aggressively.

Carl said...

No - it's frosty here tonight, and will be on and off until April... Whenever I finish some cement work I cover it up with old curtains/blankets after wetting it down well. This tends to keep the temperature up OK if we're only getting an air frost or a light ground frost. I'm currently building the 'summer house' that the oven will sit inside, to give me a way to work under cover. If it gets really cold (sub zero) I'll stop building for a bit - I'm not in that much of a hurry!