VENTO - Stonebake Oven Company

[highlandladdi]

You can buy vermiculite from most builders merchants, I used the WFO forum discount at Jewsons which worked out well. Mixed it 8 parts ish to 1 part cement and there you have it: Vermicrete!

Make it a nice and thick layer though. It's cheap to make and does a bloody good job. I went for about 4-5 inches and it worked for me, but some will say even more.

After the Vermicrete sets, give it a render with some waterproof additive in it, and you'll have no problems.

Mine has lasted through winter, with temps lower than -15°C and I've got no cracks. The render is not even warm to the touch when it's fired up, and a few inches away you've got 500°C. Amazing

[xavster]

Pardon my ignorance - is the vermicrete instead of insulation blanket and chicken wire?

[oblertone]

Jun 3, 2015 20:00:17 GMT xavster said:

Pardon my ignorance - is the vermicrete instead of insulation blanket and chicken wire?

Yes it can be, although some folk use both you can just use vermicrete over your dome, you just need approximately twice the thickness to achieve the same result.

Oddly enough loose vermiculite has even better insulation properties but you do need to contain it with walls or some other enclosure. We used 4" of loose over molten zinc and you could put your bare hand on the surface, although it wasn't recommended 

You can also buy loose vermiculite in garden centres where it is 10 x the price of a builders merchant.

[tonyb]

Its not really odd about loose vermiculite being better, its essentially the air that is the insulator, loose vermiculite has lots more air per equivalent volume of vermicrete.