High temperature calcium silicate boards generally cost more than regular calcium silicate boards for several reasons:

Higher purity materials

High temperature boards use purer grades of calcium silicate and cellulose fibers that can withstand higher temperatures. This makes them more expensive to produce.

Special additives

They often contain special heat resistant additives like aluminosilicates, graphite or vermiculite to improve their high temperature performance. These additives add to the cost.

Thinner sections

High temperature boards sometimes need to be made in thinner sections to achieve the required high temperature resistance. Thinner boards require more material per square meter, increasing costs.

Lower production volumes

Since high temperature calcium silicate boards have a more niche application, they tend to have lower production volumes. This can make them more expensive on a per unit basis.

Specialized manufacturing

The production processes and equipment used to manufacture high temperature boards that can withstand 650°C to 800°C often requires more advanced technology. This is reflected in the cost.

As an example, a regular 50 mm thick calcium silicate board for ambient temperature applications may cost around $1 to $2 per square foot. A comparable 50 mm thick high temperature board capable of 800°C may cost around $3 to $5 per square foot – so around 2 to 2.5 times higher in cost.

The price difference can be even more pronounced for higher thickness boards of around 100 mm, where the high temperature version may cost 3 to 5 times more than the regular board.