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David Paterson 10-17-2004 02:15 PM

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 2600F 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

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


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


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


Inswool HP Blanket

6 lbs/cu.ft

8 lbs/cu.ft.

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


Kastolite 30 LI
90 lbs/cu.ft.


Mizzou Castable
139 lbs/cu.ft.


Greencast 94
163 lbs/cu.ft.


10-17-2004 04:04 PM

David this was a valuable contribution. The information is out there but needs to complied and presented like this for comparison.
Not too many years ago electric melting was very experimental. Industry had used it for years but getting down to the studio level took time. The contollers had to be discovered and every way of using electricity required experimentation.
Right now in fuels, everything except natural gas and propane seem to have the "alternative" label. Once again though industry has worked all of this out on their scale just not on ours. The same is true for recuperation. Economics is driving us to be exploratory and experimental but we aren't really creating nuclear fusion. Fortunately, we can get most of the high tech materials and refractories if we can find out about them. It is putting all of these together that will give us the best results. Every time I rebuild, I do it differently. I am running a studio now for less than three times what it cost in 1972. With our recent cost increase, propane is over eight times as expensive as it was then. Materials, design and some innovation are all pieces in the puzzle.

10-17-2004 04:12 PM

One more to check out is Microporuos Insulation from Thermal Ceramics. Henry pointed this one out a while back. They claim it has the "lowest thermal conductivity of any known insulation". It comes in a variety of forms including a hand formable BTU-GUE. I didn't see any numbers on it though.

Franklin Sankar 10-17-2004 06:43 PM

Do you have to ridigize the the micropore fibre ?

Henry Halem 10-17-2004 09:06 PM

New Age
Microporuos is the heading of the line of insulating materials sold by Thermal Ceramics. It is an insulating material unlike any other type of material any of us are used to. The subheading that is applicable to us is the line called Flexible Min-K._Specifically you will look at the MIX F150 and MIX F182. You can find it at the following link. Oh yes Franklin, no don't rigidize it.


David Paterson 10-18-2004 12:26 AM

I edited my original post to include the figures for one of the Microporuos Insulation products from Thermal Ceramics, BTU Block Board.

It seems fairly pricey:

So I was wondering if Henry, or anybody else has any direct experience with it. The heat loss figures are about a third of the Skamol Board, which had been the best of the lot. The question is whether the incredible heat loss figures actually work in practise.

You can download a data sheet about it and other Thermal Ceramics products here:

Donovan Brooke 10-18-2004 01:24 AM

David, thanks for this post... good points to consider.


Henry Halem 10-18-2004 10:20 AM

Yes I believe the heat loss figures put out by TC are accurate. We use about 1/2 inch on the crown of the EZtherm furnace and considering it in other locations as well. You have to be careful though where you put it as it max's out at about 1800 deg. F. so you do not want to put it in any area that gets to that temperature, directly on furnace crowns, etc. We now use it as the last layer of our crown. It is my belief that in some situations the energy savings $$$$$ will more than pay for the upfront cost. It is fragile to the degree that one should handle it carefully. It is the type of material that does not bend easily although it will somewhat. It is best used in flat crown or wall situations. The space saving from standard fiber is terrific.

Edward Dluzen 10-18-2004 11:24 AM

Additionally there is from Zicar

MICROSIL Microporous Insulation

Max Use Temp 1742F

68F .132
392F .145
752F .173
1112F .208
1472F .263

Alumina Mat

Max Use Temp 3002F

315F .50
1000F .77
1400F 1.03
1796F 1.33
2192F 1.65
2597F 2.15

Alumina Blanket Type AB & MB

Max Use Temp 2912F

599F .50
1000F .70
1400F .90
1796F 1.25
2192F 1.60
2597F 2.15

Alumina-Silica Blanket Type ASB-2300 & ASB-2600

Max Use Temp 2300F and 2600F

Bulk Density of 4 pcf

500F .56
1000F 1.13
1500F 1.96

Bulk Density of 6 pcf

500F .45
1000F .94
1500F 1.70
2000F 2.80

Bulk Density of 8 pcf

500F .39
1000F .78
1500F 1.31
2000F 2.02

Bulk Density of 10 pcf

1000F .73
1500F 1.17
2000F 1.72

Alumina Insulation Type ZAL-15 & ZAL-15AA board

Max Continuous use 2822F & 2732F

482F .40
977F .60
1472F .90
1967F 1.30
2282F 1.70
2462F 1.80

Alumina-Silica Insulation Type AXL Board

Max Continous Use 2300F

752F .80
1472F 1.20
2012F 1.50

Alumina-Silica Insulation Type AXHTM Board

Max Continous Use 2600F

752F .60
1472F 1.00
2012F 1.70

There are a few more if anyone is interested.


Edward Dluzen 10-18-2004 11:28 AM

Now we need to compare material cost vs savings in energy/payback time for the more expensive but better insulations.


Edward Dluzen 10-18-2004 11:47 AM

There is a program

That is a neat program you have to pay for it, but it looks interesting, for calculating cold face temperatures of various materials layered or not.

There is a free sample running download.

Has anyone used this program? Or seen it?

I am not affliated with this in any way, unless I can get one for free.....


David Paterson 10-18-2004 12:43 PM

One issue in designing furnaces for minimum heat loss is the following issue:

If you replace 6" of Kastoloite 30 with 3" of IFB which has one half the heat loss, is this a break even situation?

Logic would say that since the Kastolite furnace is much larger on the outside, the larger radiating area would loose more heat. But how much more?

The issue becomes important when you look at using an expensive product like the microporous insulation in place of several inches of 6 lb fiber, which is very cheap.

Does anybody have either theoretical or practical knowledge on this issue? If you spend a lot of money on high tech materials, are you just saving space, or is there substantial real savings on energy consumption?

David Paterson 10-18-2004 01:07 PM

In regard to Zircar products, they are usually quite pricey.

The Thermal Ceramics BTU-Block Board works out to $13.90 per sq ft for one inch thickness from this website:

The Zircar Microsil Microporous Insulation works out to over $25.00 per sq ft in one inch thickness from the Zircar website:

Franklin Sankar 10-18-2004 01:22 PM

Please allow me to tell a story related to your post.
I just got a piece of grey boad and was told that it is silicaboard and the btu/ft hr deg F is .11 at 1832 F. That sounds too good to be true. Is that posible. Any guesses what it is?
They are building a new plant and I get to wallow in the garbage, found some scraps no specs and no one will say what it is.
Its a pig delight now to find some ears to show Pete.

Is there such a thing as silica board that can go up to 2300F?


Ed Skeels 10-25-2004 12:56 PM

Harbison Walker Heat Program
1 Attachment(s)
An online application is available on the Harbison Walker website to calculate heat loss. You need to register and wait for a password. Its free. Image of results form below.

David Paterson 10-25-2004 02:11 PM


Where exactly on the Harbison Walker website is the program to calculate heat loss?


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