High-Temperature Insulation

Choosing High-Temperature Insulation by Material, Form & Duty

High-temperature insulation materials differ not only in maximum temperature capability, but also in thermal conductivity, density, rigidity, flexibility, thickness and resistance to mechanical exposure. A board used to construct a fireplace enclosure performs a different function from a fibre blanket lining a furnace, a vermiculite heat shield or a flexible insulation layer wrapped around pipework.

Select the material according to the thermal function required at its installed position, then confirm that its temperature class, physical format and installation method are appropriate for the complete system.

High-Temperature Insulation Families

Insulation type	Form	Key characteristics	Typical applications
Insulation Construction Boards	Rigid boards	Low thermal conductivity, accurate panel construction and heat-resistant enclosure capability	Fireplace chambers, stove surrounds, false chimney breasts, heat shields, kilns and compatible thermal equipment
Vermiculite Boards	Lightweight rigid panels	Low thermal conductivity, easy cutting and shaping, grades rated up to 1100°C	Stove linings, register plates, heat shields, fireplace chambers, range cookers and suitable hobby kilns
Loose-Fill Vermiculite	Lightweight granular insulation	Fills enclosed voids and irregular spaces without forming a rigid structural layer	Behind firebacks, around suitable pipework and within compatible insulated cavities
Glass Fibre Insulation	Flexible felt, wrap and textile formats	Flexible thermal insulation for moderate-temperature duties; product temperature limits vary by construction and coating	Flues, pipes, ducts, removable insulation, thermal barriers and protective wraps
Biosoluble Fibre Insulation	Blankets, boards and papers	Low-mass high-temperature insulation with low thermal conductivity and low-biopersistence fibre technology	Kilns, furnaces, boilers, thermal processing equipment, backup insulation and sealing layers
Ceramic Fibre Insulation	Blankets, boards, papers, ropes and specialist fibre forms	Low thermal mass and high-temperature capability, including VITCAS grades rated to 1260°C and 1430°C	Kilns, furnaces, forges, boiler ducts, stacks, heat-treatment equipment and industrial thermal linings

Rigid Insulation Boards or Flexible Fibre Insulation?

The required installation geometry is one of the first factors to consider when choosing insulation.

Rigid boards are suited to applications where a defined flat surface, controlled thickness or accurately formed panel is required. Depending on the product, they can be used to create fireplace enclosures, heat shields, stove linings, baffles and rigid insulation layers.

Flexible blankets, papers, felts and wraps are better suited to curved equipment, irregular surfaces, joints, layered furnace constructions, pipework and confined spaces where rigid panels would be difficult to fit.

Rigid and flexible insulation can also be combined within the same thermal system, provided each layer is suitable for the temperature and conditions at its installed position.

Temperature Rating Is Only Part of Insulation Selection

The insulation material must tolerate the temperature it will experience, but maximum temperature alone does not determine thermal performance.

Important selection factors include:

• service temperature at the actual insulation position;
• thermal conductivity at the relevant mean temperature;
• required insulation thickness and available installation space;
• density and heat-storage capacity;
• rigid or flexible format;
• mechanical loading, vibration or gas velocity;
• direct flame or hot-face exposure where applicable;
• chemical and process atmosphere;
• fixing, encapsulation or surface-protection requirements.

A higher temperature classification can provide useful thermal margin, but it does not automatically make one insulation product better suited to every installation.

Insulation Thickness & Thermal Conductivity

Increasing insulation thickness generally reduces heat transfer, but thickness should be considered together with the thermal conductivity of the material at operating temperature.

Thermal conductivity is not necessarily constant as temperature rises. Two products of equal thickness can therefore produce different thermal results, particularly in furnaces, kilns and other equipment operating at elevated process temperatures.

Where an installation has a defined maximum external or casing temperature, insulation thickness should be determined from the complete construction rather than selected from temperature rating alone.

Fireplace, Stove & Flue Insulation

Domestic and commercial heating installations can require several different insulation functions within the same system.

• Construction boards can form compatible fireplace chambers, stove enclosures and false chimney-breast structures.
• Vermiculite boards can provide lightweight stove linings, heat shields and register plates.
• Loose vermiculite can insulate enclosed spaces such as specified voids behind fireplace components.
• Flexible fibre materials can provide insulation around suitable flues, pipework and other heat-exposed components.

The material used directly beside a hot appliance may have different requirements from insulation positioned behind a lining or around a flue. Check the temperature and construction at each interface rather than treating the complete fireplace or stove installation as one insulation zone.

Kilns, Furnaces & Industrial Thermal Equipment

Industrial insulation systems frequently combine several refractory and insulation layers. Dense refractory materials can provide the hot-face strength and wear resistance, while low-density boards or fibre insulation behind them reduce heat transfer and heat storage.

Ceramic fibre blankets and boards are particularly useful where low thermal mass and high-temperature capability are required. VITCAS ceramic fibre grades include products rated to 1260°C and 1430°C, while biosoluble fibre products provide an alternative fibre technology for suitable duties, with temperature capability dependent on the individual board, blanket or paper.

Typical applications include ceramic and glass kilns, heat-treatment furnaces, forges, foundry equipment, boilers, ducts, stacks and process-heating systems.

Vermiculite Insulation for Lightweight Thermal Protection

Vermiculite provides lightweight insulation with low thermal conductivity and is available in both rigid board and loose-fill formats.

VITCAS Vermiculite Boards are rated up to 1100°C and can be cut and shaped for applications such as stove linings, heat shields, register plates and suitable replacement panels.

Loose-fill vermiculite performs a different role. It is intended to fill compatible enclosed spaces and irregular voids rather than provide a rigid or load-bearing construction layer.

Glass Fibre, Biosoluble Fibre & Ceramic Fibre

Fibre composition has a major influence on the temperature range and intended duty of flexible insulation.

Fibre family	General positioning	Common formats
Glass fibre	Flexible insulation for moderate-temperature applications where the individual product specification is suitable	Felt, wrap, cloth, rope and textile products
Biosoluble fibre	Low-mass high-temperature insulation offering a low-biopersistence fibre option for compatible systems	Blankets, boards and papers
Ceramic fibre	Higher-temperature insulation for demanding industrial thermal duties	Blankets, rigid boards, papers, ropes and specialist formed products

The temperature capability of the complete product should always be checked. Coatings, foil facings, adhesives, binders or other components can have different operating limits from the underlying fibre.

Protecting Insulation in Service

Low-density insulation materials are selected primarily for thermal performance rather than abrasion resistance or structural loading. In many installations they require suitable support, fixing, encapsulation or protection from direct mechanical damage.

Fibre blankets should not be assumed to replace dense refractory linings in areas exposed to significant abrasion, impact or process wear. Likewise, lightweight insulation boards should not be treated as general load-bearing construction materials unless the individual product specification expressly provides that function.

High-Temperature Insulation Applications

VITCAS insulation technologies can be selected for a broad range of domestic, commercial and industrial thermal systems, including:

• fireplaces and stoves – chambers, surrounds, heat shields, register plates and flue insulation;
• ceramic and glass kilns – lining, backup insulation, doors and low-mass thermal barriers;
• industrial furnaces and forges – lining systems, baffles, casing insulation and heat containment;
• boilers, ducts and stacks – thermal barriers and insulation around hot process components;
• foundry and heat-treatment equipment – furnace insulation, maintenance layers and thermal containment;
• pipes and exhaust systems – flexible insulation and wrapping where the selected material suits the surface temperature.

For further background, read about thermal protection and insulation of exhaust pipes and the principles of thermal insulation and how it works.

Frequently Asked Questions

What are high-temperature insulation materials used for?

They reduce unwanted heat transfer and help protect surrounding construction or equipment in high-temperature systems. Applications include fireplaces, stoves, flues, boilers, kilns, furnaces, forges, ducts, process equipment and exhaust systems. The correct material depends on temperature, insulation duty, available space and installation conditions.

Should I use an insulation board or a flexible blanket?

Rigid boards are useful where a defined panel, flat insulation layer, enclosure, heat shield or controlled thickness is required. Flexible blankets are better suited to curved or irregular surfaces, layered furnace systems, pipework and confined spaces. Temperature capability, thermal conductivity and mechanical exposure must also be considered.

What is the difference between ceramic fibre, biosoluble fibre, vermiculite and glass fibre insulation?

Ceramic fibre is suited to demanding high-temperature duties and is available in grades including 1260°C and 1430°C. Biosoluble fibre provides low-mass high-temperature insulation using low-biopersistence fibre technology. Vermiculite provides lightweight rigid-board or loose-fill insulation, while glass fibre is typically used for lower-temperature flexible insulation, wrapping and textile applications. Individual product specifications should determine the final selection.

Can high-temperature insulation materials be cut to size?

Many boards, blankets and papers can be cut or shaped during installation. The correct method depends on the material: soft fibre products can often be trimmed with suitable cutting tools, while rigid boards may require different hand tools or saws. Follow the handling and cutting instructions for the individual product.

Does thicker high-temperature insulation perform better?

Increasing thickness generally reduces heat transfer, but the result also depends on thermal conductivity at the relevant temperature, material density, installation quality and the complete lining construction. Thickness should therefore be selected as part of the thermal design rather than in isolation.

Is the insulation with the highest temperature rating always the best choice?

No. The temperature rating must be sufficient for the intended duty, but material form, conductivity, density, thickness, mechanical conditions and installation method can be equally important. A 1430°C flexible blanket, an 1100°C vermiculite board and a rigid fireplace construction board solve different insulation problems.

Can lightweight insulation replace dense refractory material?

Not automatically. Lightweight insulation is primarily selected to control heat transfer and heat storage, while dense refractory materials can be required for hot-face strength, abrasion resistance, load support or contact with aggressive process conditions. Many industrial lining systems use both materials in separate layers.