alternative cheap insulation?

[catacomb]

I recently calculated the prices of the materials I need for my Pompeii oven and am coming well over €800 (ca. $1,140). Here in Ireland everything seems to be more expensive.

Locally sourced firebricks would cost me €3 ($4.30) each, vermiculite is at €23 ($33) per 100 litre bag (which is only about 40 cubic inch). These are really the two bad boys that are making the whole thing expensive.

Anyways to get to the point I really need to save materials and to save on vermiculite I was thinking about walling in the dome and filling it with something cheap, maybe sand or rockwool as insulation. I might be able to add 5cm (2 inch) of vermiculite concrete on the outside of the dome which would correlate to two bags at the very most.

Would this work?

P.s. Also if anyone has the conductivity or resistivity of the aforementioned materials or other alternatives It would be very helpful for me to calculate the u-values, thanks

[Ken524]

Don't use sand. Sand is NOT an insulator. If you can do 2" of vermiculite/cement outside the dome that would be a good start.

I'm not very familiar with Rockwool. I'm sure someone will jump in with an opinion on that. Might be ok outside the 2" of vermiculite.

[SCChris]

Rockwool also known as Stonewool is fine alternative and at least around here cost friendly. Check your local boat yard supply, foundry supply, or building supply places for availability. I was able to get 2 inch rigid Calcium Silicate board through a Foundry supply and 3.5 inch Rockwool boards, from a industrial insulation company, both at excellent pricing, I hope these will work for you as well. The Stonewool insulation around my dome took a bit of ripping and stuffing but I’m delighted at the performance. I had enough Rigid insulation left over to use it for the oven door.

Chris

[david s]

thermal conductivity of dry sand 0.16 -0.25 variability depending presumably on grain size and shape. Thermal conductivity 4:1 vermicrete is 0.16 dry vermiculit 0.06
If it were me I'd be scrounging around building sites and picking up scraps of ceiling insulation offcuts from their dumpsters, if you have a layer of vermicrete under this there should not be any issues of binders burning. This will work well for an enclosure but not for an igloo. The stuff compresses too easily to stucco over for an igloo finish.

[SCChris]

I haven't been aware of binders in Rock/Stonewool being a problem, smell or otherwise. The product available here is used and accepted in our building codes as insulation backing for residential fireplaces. It’s stable in heat and not hard to work with. I didn’t build an igloo type structure but if you are I’d recommend the ceramic blanket because of the capability to more easily wrap the round shape. You could use the Rock/Stonewool to form against the dome and I don’t believe compression would be an issue but getting the nice round igloo shape will be some work. If you’re going with an oven enclosure the Rock/Stonewool is economic and efficient.


Chris

[brickie in oz]

Originally Posted by david s

I'd be scrounging around building sites and picking up scraps of ceiling insulation offcuts from their dumpsters,

There are not too many building sites in Ireland at the minute, thats why all the Irish lads are over here working.

[SCChris]

Rockwool Limited
Unit 11
Northwood Court
Northwood Business Campus
Santry
Dublin 9
Ireland
Tel: +353 1 891 1055
Fax: +353 1 891 1056

Chris

[chidding]

Why not opt for a cheaper brick? This is how I saved alot in my project..
Sure i may not be using firebricks, but I'm sure with solid clay bricks im going to get pretty damn close.

No matter what you do.. dont skimp on insulation.. its the single most important aspect.

[GianniFocaccia]

Hey Chris,

Where did you get your stonewool? Was it really inexpensive? If I rermember, you used rigid board for your hotface.

John

[Tman1]

+1 on 'not skimping on insulation'.