The Insulation Values Of Different Materials

I decided to gather together this data in response to the recent discussion on the use of alternate fuels to run a glass studio.

My occassional sarcastic comments on that issue were based on the fact that I have yet to see a technology that I could readily put to use, and on my belief that good design using conventional fuels and known technology can gain as much if not more than 'cheaper' fuels using technology that has unknown variables and problems.

I believe electric furnaces in particular, where all the energy can be contained in a small unit that is sealed when not in use, can yield results equal to if not better than 'alternative technologies'.

Heat loss is a combination of the insulation value of the material, the square footage of the outside walls, and the leakage around doors, etc.

In a well designed electric melter, with the interior space only slightly larger than the crucible, and using the best insulation materials, the actual energy use would be substantially lower than a furnace that used waste oil that fired into a large firebox (creating perhaps 3X the interior volume), and that was insulated with higher density castable to take the extra abuse.

Replacing Kastolite 30 with 2600°F IFB would cut the heat loss almost in half on its own. Replacing 6 lb fiber with Skamol board would gain another 30%. The Skamol is also very cheap. Cutting the interior volume in half or more would also drop the heat loss substantially.

I have edited this post to add the figures for one of the Microporuos Insulation products from Thermal Ceramics, BTU Block Board.


Here Are The Insulation Values Of Different Materials
(Btu·in/hr·ft2·°F)


Insboard 2600 HD Fiber Board
26 lbs/cu.ft.
2600°F

800°F__________0.6
1200°F_________0.8
1600°F_________1.0
2000°F_________1.2


Skamol SUPER-1100 E Calcium Silicate Insulating Board
15.3 lbs/cu.ft.
2000°F

392°F__________0.49
752°F__________0.62
1112°F_________0.69


Thermal Ceramics Microporuos Insulation
BTU-Block Board
18 lbs/cu.ft.
1800°F

500°F__________0.16
1000°F_________0.21
1500°F_________0.30


Inswool HP Blanket
2300°F

6 lbs/cu.ft
600°F__________0.5
1000°F_________1.0
1400°F_________1.55
1600°F_________1.85

8 lbs/cu.ft.
1000°F_________0.8
1400°F_________1.2
1600°F_________1.4


G-26 LI Insulating Firebrick
48 lbs/cu.ft.
2600°F

1000°F_________1.9
1500°F_________2.2
2000°F_________2.6


Kastolite 30 LI
90 lbs/cu.ft.
3000°F

800°F__________3.6
1200°F_________3.8
1600°F_________4.1
2000°F_________4.4


Mizzou Castable
139 lbs/cu.ft.
3000°F

1200°F_________7.6
1600°F_________7.5
2000°F_________7.4
2400°F_________7.4


Greencast 94
163 lbs/cu.ft.
3400°F

1200°F_________16.3
1600°F_________14.1
2000°F_________13.6
2400°F_________14.5