Insulating fire bricks
Insulating fire bricks are soft and light in weight. They can be easily cut by handheld hack saw or any other hand tool like chisel or even drill bit. Color of insulating bricks varies but usually they come in shades from light brown to white, see pictures. In refractory air is the best insulation and this is why insulating firebricks have excellent insulating properties. Their body is made of tiny air spaces similar to honeycomb effect.
How to use light weight fire bricks insulation
Use of light weight fire brick insulation is broad, mainly in industrial and hobby kilns heated up with either electric spiral elements or gas burners, furnaces, both for hot face lining or outer back-up heat insulation.
IMPORTANT:
Do not confuse lightweight insulating fire bricks with heavy dense firebricks. Insulating bricks are refractory too and of course withstand very high temperatures range BUT for purpose they have very low thermal conductivity and don’t absorb the heat well at all. 
Those are intentions for heat insulation. For instance if you used them for building of the hot face in a wood fired oven (for cooking) the oven wouldn’t cook, because it wouldn’t store and hold almost any heat. You can however use these insulating fire bricks on the outer side (of the heavy firebrick walls, vault or under the floor bricks and slab) to prevent the soaked in heat in the chamber’s body mass from escaping and achieving superb results. Meaning well insulated oven which will hold the absorbed heat in its mass, where it should be to cook for long time.
TYPICAL TECHNICAL DATA
Insulating Fire Bricks’ Physical Properties
- Bulk Density : 604 Kg/m³
- Modulus of Rupture : 1.52MPa
- Permanent Linear Change on reheating 24hrs. @ 1280°C : 1.95%
- Cold Compressive Strength : 2.01 MPa
- Thermal Conductivity 300°C : 0.2 W/m.°K
- Thermal Conductivity 750°C : 0.28 W/m.°K
- Thermal Conductivity 1000°C : 0.32 W/m.°K
Chemical Composition of Insulating Fire Bricks
- Alumina : 37%
- Silica : 61%
- Ferric Oxide : 1.6%
Light weight bricks for insulation can be purchased by public in pottery supplies shops.
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I am looking for the light weight brick block of 15″ X 8″ X 4″ size insulating block having strenght as good as common brick. Suppliers may contact me.
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My firm manufactures this type of high heat resistant insulating firebrick brick units.
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I build heat treat oven. Need type k23 fire bricks.
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I have been looking into insulating fire bricks for some time now and this has been a great resource for me. Thanks for the info
Drew
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How can i recognise heavy dense fire brick from lightweight insulating fire brick ? I need it for wood burning pizza oven. Tks for helping
added by Rado: Email me one photo of the brick in question and I will tell you which type it is. Close up large image is better for seeing clearer details. It’s very easy to recognize light f’brick for insulation from the other heavy type you need for the heat absorption. Did you get a chance to hold it or can you cut the brick in half for instance with any hand saw – how does it go?
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You can tell the dense bricks and insulation bricks on their surface. There are some small holes in the surface of insulation bricks, this is why insulating firebricks have excellent insulating properties as Mr Rado said, while if you find some holes on the dense brick, it means it is not a good dense brick. Also a standard insulation brick’s weight is about 0.85kgs~1.7kgs(size is: 230x114x65mm), but the dense brick ‘s weight will be 3.5-4.3kgs per pc. Hope it can help you. Eric Hou From China
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We manufacture special, low cost FIRE BRICKS (ex New Zealand) for pizza ovens, fire places, wood burners and the like. Composition has proven, 30 year history in this application.
Please check our auction website for lastest updates, new product lines, sales etc.
Thank you.
Paul Marsden
Auckland
New Zealand
email: info@firebricks.co.nz
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dear sir,
im very interest in your product from light weight fire brick and another refractory materail please if you have any catalogue or magazin about this product, send it for me on my post adress below , and thank you very much.
falah abdulla farhan
iraq-anbar- falluja
falluja post center
p.o.b \ 28
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Thanks for publishing this helpful information on insulation bricks. I am working on building a Custom Kamado Oven/Grill (Similar to Big Green Egg). Can anyone suggest where I can find a consultant or ceramic engineer to help me select the proper Insulating Materials? I will assume that the chemical composition listed on this page (Alumina : 37%, Silica : 61%, Ferric Oxide : 1.6%) are the way to go. I realize these need to be casted and fired in a kiln. Anyone can help? .. Let me know how I can hire you.
I live in Canada.
Thanks,
Jonah
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I am looking for brick that will go to 3000 to 3200 F. with dimensions of 2.5″ x 4.5″ x 9″ and hopefully be semi light weight? I am looking to buy 400 bricks with possible future orders. Please contact me at tiemann66 @ yahoo.com.
Thanks!
Ryan Tiemann
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I am researching insulating firebrick’s physical properties, especially the bulk density insulating firebricks have; weight per specific volume to determine insulation properties of the material. I got it all on this page, I’m building ceramic kiln. Thank you. Peter
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Is it true that every few years these insulating firebricks need to be replaced with new one? What do you do with old used insulating firebricks? If it needs to be disposed, are there specific locations you need to send it to??
-Thanks-
added by Rado:
Mei,
It really depends on conditions a kiln or a furnace is being used. There are also different grades of insulating firebricks whose are used at various conditions and temperature cones/levels. For instance; if the temperature reaches the top or even above the high mark what the insulating firebricks are meant to withstand in, and continuously, their life span will be shorter. Otherwise one of the kilns I made reaches very near the upper temperature allowed for the bricks, plus it is being fired two times each week for 7 years now, and still the insulating firebricks it is made of aren’t showing much of a wear at all. Only electric heating spiral elements in this kiln were replaced couple of times.
These insulating firebricks are made from natural safe clay. These can disposed ordinarily. UNLESS of course they were used in a furnace which comes in contact with nasty chemicals therefore the bricks could be contaminated with some toxins, then dispose accordingly e.g. in an industrial waste place.
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What is the maximum temperature rating of these bricks? I’m thinking about using them for a furnace that melts iron and steel, this would require at least 3000* F (16-1700 *C if I remember right). Would these insulating fire bricks be enough to handle that amount of heat if there was, for example, a 1/2″ of high heat refractory cement applied on the inside of the bricks for the furnace?
added by Rado:
Michael,
Nice knives, I looked at your website. Would you like to see heat treating furnace design I made for making knives (not for melting), and some knives that were made in it?
Best would be to line the inside walls of your furnace with the heavy-dense firebricks with appropriate alumina content for the temperature range you use. To let them cope with the hot face generated. And then these light in weight soft insulating firebricks on the outside for insulation. Then the inside lining can be easily replaced once necessary.
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I am thinking of using a layer of insulation firebricks over the heavy dense firebricks for my outdoor wood burning pizza oven. It rains frequently here in Malaysia and I do not think the insulation bricks will last long without some form of protection. I do not want a roof over the pizza oven so I am thinking of using a layer of stone tiles. Should I use refractory mortar or normal mortar?
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I wish to clarify that the stone tiles will be applied over the insulation bricks.