Vermiculite in bags used for insulation I pay 24 bucks per 1x 100L bag (3.53 cu-ft), you will need more of them for insulating of the whole oven as per below described quantities.

What is Vermiculite? Insulation applications.

Where to buy vermiculite insulation? Best places to find vermiculite containing products, or most importantly dry loose-fill vermiculite insulation in bags, are large landscaping yards (because in horticulture the vermiculite, as well as Perlite, are used to prevent soil compaction or as soil conditioner/amendment after adding a composting matter.) Pool shops and businesses that build and install swimming pools also work with large quantities of vermiculite.

Then obviously those who work with different kinds of insulation materials. Such as; refractory firms (handling mostly refractory and high-temperature insulation) or factories producing various vermiculite based thermal insulating floor boards for use either with floor heating and without, walls, 3rd grade vermiculite size granule detailed image or floor levels construction to lower down a total weight of a building (vermiculite lightweight insulating concrete is highly suitable for building. A 5:1 – vermiculite to cement mixing ratio, it is light, insulating and, fire resistant with a great degree of sound absorption – more below). Then there are thermal roof panels and ceiling insulating layers, these are durable plus moisture resistant goods. Not to mention a packing material or even incubation of eggs for they remain in the warmth and protected, etc., vermiculite has many practical uses.

My advise is; negotiate with different suppliers what you’ll be charged for ~10 bags of vermiculite versus any price for one bag to source a much better deal. However, these jobs can be very easily done using a lot more cost effective and suitable insulating materials that will save you; and with the same or even better insulative properties than Vermiculite or Perlite have (with no material efficiency compromises, they do what they’re intended to do in kilns, furnaces or ovens with no quality reduction.)

Comparing the insulating lightweight concrete produced by mixing vermiculite and cement, depending on how it is mixed, this concrete is around 80% to 90% less heavy in weight sense, per same volume, than a conventional heavy/hard concrete. One inch or 25.4mm of vermiculite insulation layer thickness will have the equal insulating property values as 508 millimeters – 20″ thick regular concrete layer has. How is that for an interesting differences in material?

More on Vermiculite heat insulation and the quantity required.

I am using both US and Metric measures for the quantity explanation.

From the industry/manufacturers, dry loose vermiculite comes in sizes from 1 to 4 grade. Each number is intended for different purposes. One 100 liters bag of granulated No. 3 grade vermiculite (not dust) weighs close to 9 kilograms – which is 90kg/cu meter. Although much lighter in larger granules form exists, example is the No. 4 Grade, it has bulk density from 65kg/m3 up. The dust or tiny vermiculite packed, the first grade 1, is heavier around 160kg/m3 and it is not suitable for our reasons.

To be precise, I don’t often refer to loose vermiculite in bags as pellets. I think, typically pellets are created by compressing of small material particles, or mixture of materials, into denser pellets. This insulation material produced is expanded exfoliated vermiculite, very light, low heat absorbent, not compressed nor heavy.

Insulation with vermiculite vermiculite insulation

Lighter in weight is better” is the rule for insulating. Plus any extra thickness applied on top, is only for an extra degree of benefit. It depends on the size and how they pop it; crushed volcanic mineral rock goes into kilns and in the heat they pop it just like a pop corn in the heat. The result is the mineral puff enlarges, expands into vermiculite in the heat and becomes that light.

1 cubic meter = 35.3 cu feet (0.1 cu m = 3.53 cu ft)
1m3 = 1000 Liters (0.1 cu m = 100L)
1 cubic meter = 264.17 US Gallons

For the whole job, when using vermiculite for the insulation that is, I buy 7x 100 Liters bags (larger bulky but lightweight paper or plastic bags.) 700L makes it 25 cubic feet (or exact measure convert is 24.717 cu ft equals 700 Liters). The amount is same for both Swishy and Masterly Tail oven designs.

Insulating with vermiculite work with vermiculite insulation

This is amount for extra insulation layer added especially on the oven top. The job can be done with only 6 bags too but of course it is always better if more insulation thickness is applied. If you purchase say 28 cu ft (790 L), or more (1 cubic meter = 35.3 cu feet), if the structure design proportionally allows, add the left over extra on the top of the cooking part for even better efficiency results. (I turned more towards using ash instead of vermiculite for cost reasons (as mentioned before it has the same insulation properties like vermiculite and Perlite.) If you DIY for single project maybe the money won’t always matter.

For the heat insulation layer under the heated floor slab and, if done that way, also for the final contours over the top; when you’re mixing your vermiculite with bonding agents, like building GP or Portland cement (same thing), add water gradually in little quantity as vermiculite doesn’t absorb water, it could become too runny otherwise. Mix by hand and shovel on a concrete ground or in a wheelbarrow, it’s very easy/straight-forward (mix not in a mixer because vermiculite granules are on a soft side and the mixer’s metal parts would surely damage its small particles.) Most ideal is to pour it simply out of the bags in its simplest loose-fill form covering all around and above if the oven was boxed in among e.g. house brick walls or in some metal casing. For vermiculite mixes here is the page dealing with heat resistant insulation applications including how to make own vermiculite based light weight concrete.

Typical physical properties of exfoliated (expanded) vermiculite

Bulk density: 4-10 lb/cu ft or 64-160 kg/m3
Temperature use: 2100-2280°F or 1150-1250°C
Non combustible.

However, if needed, you can use ash from burning coal (fossil fuel). It is sold mainly in large gardening yards (or directly from the production where it’s being burned, in hot water heating boilers, power stations; currently 80% of Au. electric power production is run on burning coal, for instance.) For the comparison, this ash costs only 35 bucks to fill my UTE and the amount will suffice for insulating 4 ovens. When I am able to source it closer to a job I always use it as it performs just the same in these temp. heat conditions like either Vermiculite or Perlite plus it saves me.

*** Let me know a price you got for vermiculite or the ash when you locate it. If you can also who sells it (address/phone web contacts) I will find the info useful when building/insulating around your location area.