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IS 13666 : 1993Design and installation of thermal insulation for refrigeration and air conditioning systems - Code of practice

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ISO 12241 · BS 5422 · ASHRAE Handbook—Fundamentals 2021, Ch. 23 & 24
CurrentFrequently UsedCode of PracticeBIMMEP · Insulation Materials
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OverviewValues4InternationalTablesFAQ4Related

IS 13666:1993 is the Indian Standard (BIS) for design and installation of thermal insulation for refrigeration and air conditioning systems - code of practice. This code of practice provides guidelines for the design, material selection, and installation of thermal insulation for HVAC and refrigeration systems. It focuses on calculating the required insulation thickness to prevent surface condensation and minimize energy loss. The standard also details the correct application of vapor barriers and protective finishes.

Provides guidance for design and installation of thermal insulation in refrigeration and air conditioning systems.

Overview

Status
Current
Usage level
Frequently Used
Domain
MEP — Insulation Materials
Type
Code of Practice
International equivalents
ISO 12241:2022 · ISO (International Organization for Standardization), InternationalBS 5422:2009 · BSI (British Standards Institution), UKASHRAE Handbook—Fundamentals 2021, Ch. 23 & 24 · ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers), USANAIMA National Commercial & Industrial Insulation Standards (MICA Manual) · NAIMA (North American Insulation Manufacturers Association), USA
Typically used with
IS 3346IS 12436IS 8183IS 3677
Also on InfraLens for IS 13666
4Key values3Tables4FAQs

BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.

Practical Notes
! The correct placement and sealing of the vapour barrier on the 'warm' side of the insulation is the most critical step to prevent condensation, insulation failure, and corrosion.
! Ensure all penetrations, joints, fittings, and supports are meticulously insulated and sealed, as these are common points of failure (thermal bridges).
! The selection of insulation should consider operating temperature, fire safety requirements (especially for ducts in plenum spaces), and compressive strength (for pipe supports).
Frequently referenced clauses
Cl. 4Design ConsiderationsCl. 5MaterialsCl. 6Thickness of InsulationCl. 7Installation of InsulationCl. 8Vapour BarriersAnnex A - Recommended Method for Calculation of Thickness of Insulation
Pulled from IS 13666:1993. Browse the full clause & table index below in Tables & Referenced Sections.
polyurethane foam (PUF)expanded polystyrene (EPS)nitrile rubberglass woolrock woolvapor barrier

International Equivalents

Similar International Standards
ISO 12241:2022ISO (International Organization for Standardization), International
HighCurrent
Thermal insulation for building equipment and industrial installations — Calculation rules
Provides detailed calculation methods for heat transfer and insulation thickness, a core component of IS 13666.
BS 5422:2009BSI (British Standards Institution), UK
HighCurrent
Method for specifying thermal insulating materials for pipes, ductwork, tanks, vessels, and equipment operating within the temperature range -40°C to +700°C
A comprehensive code of practice for specifying and applying insulation on mechanical systems, very similar in intent to IS 13666.
ASHRAE Handbook—Fundamentals 2021, Ch. 23 & 24ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers), USA
HighCurrent
Chapter 23: Insulation for Mechanical Systems; Chapter 24: Thermal Properties of Building Materials
Serves as a global de-facto standard providing the foundational theory, material data, and design guidance for insulation systems.
NAIMA National Commercial & Industrial Insulation Standards (MICA Manual)NAIMA (North American Insulation Manufacturers Association), USA
MediumCurrent
National Commercial & Industrial Insulation Standards (often called the MICA Manual)
Focuses heavily on the practical installation and application details for various insulation systems, complementing theoretical codes.
Key Differences
≠IS 13666 uses the term 'vapour barrier' and implies near-zero permeance without specifying a quantitative value. Modern international standards (e.g., ASHRAE) use 'vapor retarder' and classify materials by their measured water vapor permeance (e.g., Class I, II, III), allowing for more precise engineering design.
≠IS 13666 is highly prescriptive, providing tables of recommended thicknesses. While useful, this is less flexible than the approach in standards like ASHRAE 90.1, which sets minimum performance requirements and allows designers to use calculation software (like that based on ISO 12241) to prove compliance with various materials.
≠The Indian standard references material specifications from the early 1990s or before. International equivalents reference current ASTM, EN, or ISO material standards, which are regularly updated to include new materials, improved test methods, and critical performance data like fire safety ratings (e.g., EN 13501-1).
≠International standards like ISO 12241 provide more sophisticated and detailed calculation methods, accounting for factors such as thermal bridges at hangers and supports, the effect of surface emissivity on the surface heat transfer coefficient, and multi-dimensional heat flow, which are simplified in IS 13666.
Key Similarities
≈All standards share the same fundamental objectives: controlling heat gain/loss for energy efficiency, preventing surface condensation to protect assets and control mold growth, and ensuring personnel safety from extreme surface temperatures.
≈The core physical principles and formulas for calculating heat transfer through insulation (based on Fourier's Law of Conduction) and determining the dew point temperature are common across all standards.
≈All standards for sub-ambient (cold) systems emphasize the critical importance of a continuous, well-sealed vapor retarder/barrier on the warm side of the insulation to prevent moisture ingress, which degrades thermal performance and causes system failure.
≈The recommended general application practices, such as ensuring tight butt joints, sealing all seams and penetrations, and providing a protective outer jacket or cladding against mechanical damage and UV radiation, are conceptually identical.
Parameter Comparison
ParameterIS ValueInternationalSource
Vapor Retarder Performance (for cold pipes)Described as a 'vapour barrier' made of materials like aluminum foil or bitumen; no quantitative permeance value is specified.Defined as a Class I Vapor Retarder with a permeance of ≤ 0.1 US Perms (or approx. 5.7 ng/Pa·s·m²).ASHRAE Handbook / ASTM E96
Assumed Surface Heat Transfer Coefficient (Still Air)8.7 W/m²K (Clause 4.2.3.2)Varies by emissivity, orientation, and temperature. A typical value for a horizontal pipe with medium emissivity is ~9.5 W/m²K.ISO 12241:2022 (Table A.1)
Insulation Thickness: 50mm Pipe, 5°C Fluid, 35°C/75%RH~25mm (for PUF, k=0.023 W/mK), calculated to prevent condensation.1.5 inches (38mm) is the prescriptive minimum for energy code compliance, regardless of ambient conditions.ASHRAE 90.1-2019 (Table 6.8.3-1)
Thermal Conductivity GroupingProvides k-values for specific generic materials (e.g., Mineral Wool, PUF) in its tables.Specifies insulation thickness based on k-value ranges (e.g., 0.030-0.035 W/mK), allowing any material that meets the criteria.BS 5422:2009
Design Ambient Condition for Condensation (Example: Hot/Humid Climate)Often suggests a fixed severe condition, e.g., 40°C and 80% RH.Uses location-specific weather data, e.g., the 1% or 0.4% occurrence design dew-point temperature for a specific city.ASHRAE Handbook—Fundamentals
⚠ Verify details from original standards before use

Key Values4

Quick Reference Values
Thermal conductivity (k-value) of Polyurethane Foam (PUF) at 20°C mean temp0.023 W/m.K
Thermal conductivity (k-value) of Mineral Wool (Rock/Slag) at 50°C mean temp0.042 W/m.K
Typical water vapour permeance for Aluminum Foil (0.05mm)0.02 perms
Minimum thickness for vapour barrier (Aluminum foil)0.05 mm
Key Formulas
q = (ti - ta) / (Rs + Rt + Ra) — Heat flow per unit area
t = k * [ ( (ti - ta) / q ) - (Rs + Ra) ] — Calculation of insulation thickness (t)

Tables & Referenced Sections

Key Tables
Table 1 - Recommended Maximum Thermal Conductivity (k-values) at Mean Temperatures
Table 2 - Typical Water Vapour Permeance of Materials
Table 3 - Surface Heat Transfer Coefficient (h)
Key Clauses
Clause 4 - Design Considerations
Clause 5 - Materials
Clause 6 - Thickness of Insulation
Clause 7 - Installation of Insulation
Clause 8 - Vapour Barriers
Annex A - Recommended Method for Calculation of Thickness of Insulation

Related Resources on InfraLens

Cross-Referenced Codes
IS 3346:2018Thermal Insulation of Buildings - Code of Pra...
→
IS 12436:1988Specification for rigid polyurethane (PU) foa...
→
IS 8183:1993Specification for rigid mineral wool thermal ...
→
IS 3677:1998Fittings for Copper and Copper Alloy Tubes
→

Frequently Asked Questions4

What is the main purpose of insulating cold pipes?+
To prevent surface condensation by keeping the outer surface temperature above the ambient dew point, and to reduce unwanted heat gain into the system (Clause 4.1).
Where is the vapour barrier installed?+
On the warm side of the insulation (i.e., the outermost layer for cold pipes/ducts) to stop ambient water vapour from reaching the cold surface (Clause 8.2).
How is the required insulation thickness determined?+
It is calculated based on the fluid temperature, ambient temperature and humidity, pipe/duct size, insulation's thermal conductivity (k-value), and the desired surface temperature (Annex A).
What kind of protection is needed for outdoor insulation?+
Outdoor insulation requires a weather-proof and mechanically durable finish, such as aluminum or stainless steel cladding, to protect it from rain, UV radiation, and physical damage (Clause 7.7).

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