What is the most important property for a thermal insulator?

Thermal conductivity (k-value). A lower k-value signifies a better insulating material. (Clause 5.2.1)

Does this code specify the required insulation thickness for a building?

No, this is a guide for selecting materials. For required thickness or total thermal resistance (R-value), refer to codes like the Energy Conservation Building Code (ECBC) for your climatic zone.

How do I choose between two materials with similar thermal performance?

Consider other factors listed in the guide, such as fire resistance, moisture resistance, compressive strength (for floors/roofs), cost, and ease of installation. (Clause 4)

What is the main difference between EPS and XPS insulation?

Both are polystyrene, but XPS (extruded) generally has lower thermal conductivity, higher compressive strength, and superior moisture resistance compared to EPS (expanded) of a similar density. (Table 1)

IS 8617

: 1994

Guide for selection of insulating materials for buildings

CurrentSpecializedGuidelinesBIMArchitectural · Insulation Materials

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This guide provides criteria for selecting thermal and acoustic insulating materials for buildings. It outlines key properties like thermal conductivity, fire resistance, and moisture resistance, and presents typical values for common materials to aid designers and engineers in making informed choices.

Provides guidance on selecting appropriate thermal insulating materials for buildings.

Quick Reference Values

Thermal Conductivity of Glass Wool (16-96 kg/m³)0.031 - 0.043 W/m.K

Thermal Conductivity of Expanded Polystyrene (EPS) (15-30 kg/m³)0.034 - 0.046 W/m.K

Thermal Conductivity of Extruded Polystyrene (XPS) (28-45 kg/m³)0.029 - 0.036 W/m.K

Service Temperature of Mineral Wool/Rock WoolUp to 750 °C

Service Temperature of Expanded Polystyrene (EPS)Up to 75 °C

Key Formulas

R = d / k — Thermal Resistance (where d is thickness, k is thermal conductivity)

U = 1 / R_total — Overall Heat Transfer Coefficient (where R_total is the sum of all resistances in a building assembly)

Practical Notes

The primary purpose of this standard is to compare materials; for mandatory thermal performance requirements (R-values), refer to the Energy Conservation Building Code (ECBC).

Always consider moisture management. Many insulation types require a vapour barrier, especially in humid climates or for below-grade applications, to prevent degradation and mold growth.

Fire properties are as important as thermal properties. Check ratings for flame spread and smoke development, especially for materials used in interiors or exit pathways.