MI Spec > Appendices > Appendix B

Perlite (or Expanded Silica)


Perlite masonry insulation is an inert volcanic rock expanded by a special heat process and is often treated with water repellent material. The resulting granular product is lightweight with countless tiny, sealed air cells, which account for its excellent thermal performance and fire resistance. It also has very high water repellency, and sometimes used where there are risks of moisture ingress. It is most common in industrial applications; in non-industrial settings, calcium silicate is more common. Perlite insulation has been proven over a period of many years in the insulation of storage tanks for liquid gases at temperatures as low as -240°C. The material is very brittle, consequently it is difficult to work with, resulting in higher labour costs.

Physical Properties

Installed Cost Ref Density Max working temp Thermal Conductivity
Med-High 48 kg per cubic meter 650 ºC 0.071 W/m*ºK
UV Resistance Flame Spread Smoke Developed Compressive Strength
High 25 <50 500 kPA (or 73 PSI)

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