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Insulating fire bricks

Light weight insulating firebricks insulation. 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.

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. Lightweight insulating fire brick. 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.


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.

Respond to the Insulating fire bricks article:


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  2. 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.

    By chirag gajjar

  3. My firm manufactures this type of high heat resistant insulating firebrick brick units.

    By Doshi Binny

  4. I build heat treat oven. Need type k23 fire bricks.

    By ott's stockade/terry ott

  5. 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

    By Insulating firebricks.

  6. 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?

    By Fire bricks insulating vs dense

  7. 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

    By dense bricks & insulation bricks

  8. 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. See the bricks here.

    Please check our auction website for latest updates, new product lines, sales etc.

    Thank you.
    Paul Marsden
    New Zealand

    By FIRE BRICKS for pizza ovens/fireplaces etc

  9. 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

    By catalog or magazine

  10. 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.


    By I am looking to make a custom Kamado Oven/Grill

  11. 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 @
    Ryan Tiemann

    By 48" borosilicate glass kiln

  12. 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

    By Bulk density of insulating firebricks

  13. 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??


    added by Rado:
    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.

    By Mei

  14. 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:
    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.

    By JMichael Hajek

  15. 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?

    By Johann

  16. I wish to clarify that the stone tiles will be applied over the insulation bricks.

    By Johann

  17. […] refractory bricks, heat resistant bricks, heavy/dense kiln bricks (to distinct them from the light in mass insulating kiln firebricks) and so […]

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  19. Hi, I live in Canada.
    Can anyone tell me if those bricks could be used to thermically isolate a home at below freezing temperatures. I understand the mortar may create a thermo bridge. However, have anyone thinkered with the idea?

    By Energiaus

  20. Hi I’m looking to build a custom bbq and needed light fireproof brick that are 10-12 mm thick and 10-15 cm width and about 30 cm length.
    Looking forward to hearing from you asap.

    By Alli

  21. Thanks for someone is finally talking and making sense about these insulating fire bricks type. Indeed firebricks for thermal insulation are much softer and lighter in their mass/weight. These are not NOT that hard so they can be easily cut by any handheld saw nor would they be heavy like the fireplace firebricks as then they would absorb the heat energy into them. Insulation firebricks do not suck heat in not would these light bricks conduct or transfer heat energy. Wonderful alike thermostatic control product as to keep precious heat energy inside the kiln cube!

    By Alena

  22. How to mortar fire the light weight type soft insulating firebricks around a wood burner?

    By Ellis

  23. How are these bricks different/better from AAC blocks (blocks made from the Autoclaved Aerated Concrete) with respect to their temperature/fire resistance and weight? For kilns can we use AAC instead?

    By Mamn

  24. How much for a box of light soft insulating fire bricks for kiln, the one above, a box of 24 firebricks. Going to used to make small kilns and having the slab about 2″ inches thick or 3″ inches.

    Internal kiln size 24 inches wide and deep by 24 inches high cube. Box of 10 insulating bricks and they must be able to stand the temperature for
    gold and silver and cooper metals melting. Looking forward to hear from some people with some prize to ship to the UK. Sign and Track the shipment delivery.

    By John Akinyele



  26. Can you please give me a price on fire bricks?

    By Taffy

  27. Dear Energiaus at comment 19: Insulating firebrick is not competitive with commonplace insulation for houses.
    For example the styrofoam insulation that I put in my attic is rated at R 11 and it is 2 inches thick with foil on both sides.
    When I phoned up the manufacturer to find out their R values they told me that R values mean Btu’s per hour per square foot per degree Fahrenheit and if you translate all of this stuff around then it adds up to about 0.026 watts/m per Kelvin, at some optimal mean temperature, or about 77 times the insulating power of insulating firebrick at 300 degrees Celsius.
    Also the data from the National Bureau of Standards would lead you to think that various insulating materials from cattle hair to corkboard tend to range from about 0.037 to about 0.049 Watts/Meter per Kelvin at ordinary temperatures. Bureau of Standards Letter Circular No. 227 cited in the Handbook of Chemistry and Physics, 48th Edition, p.E-5.

    By Peter Martyn

  28. I am looking for non fire brick for cement manufacture furnace. Maximum temperature is 1600 deg. C.

    The shape of furnace is cylindrical.

    Looking for the company that can manufacture this type of special heat brick.


    By Mehdy rahim pour

  29. Looking to insulate fire box on my smoker. Need food safe brick that will let heat / smoke move from fire box to smoking cylinder with minimal heat loss thru fire box walls.

    By Dave

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