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IS 11210:2018 is the Indian Standard (BIS) for design, fabrication and installation of ducts for air conditioning and ventilation systems - specification. This Indian Standard specifies the requirements for the design, fabrication, and installation of sheet metal ductwork for HVAC and ventilation systems. It covers material selection, duct construction, jointing, supports, and testing procedures to ensure structural integrity and airtightness.
Provides specifications for the design, fabrication, and installation of metallic and non-metallic ducts for air conditioning and ventilation systems.
Quick Reference — Top IS 11210:2018 Values
Covering duct pressure classes, material specs, fabrication tolerances, support spacing, and air leakage test acceptance criteria.
✓ Verified 2024-05-21
Reference
Value
Clause
Duct Pressure Class - Low
≤ 500 Pa
Cl. 5.1.1 (Table 1)
Duct Pressure Class - Medium
> 500 to 1000 Pa
Cl. 5.1.1 (Table 1)
Duct Pressure Class - High
> 1000 to 2500 Pa
Cl. 5.1.1 (Table 1)
Recommended Max Air Velocity (Main Ducts)— For general office/commercial applications.
10 - 15 m/s
Cl. 5.1.3 (Table 2)
Recommended Max Air Velocity (Branch Ducts)— For general office/commercial applications.
5 - 8 m/s
Cl. 5.1.3 (Table 2)
Recommended Max Aspect Ratio— Absolute maximum of 6:1 may be used in constrained spaces.
4:1
Cl. 5.1.4
GI Sheet Zinc Coating (Min)
120 g/m²
Cl. 4.1.1
GI Sheet Thickness (751-900 mm duct)— For low pressure class (≤ 500 Pa). Refer table for other sizes/pressures.
0.80 mm
Table 3
Aluminum Sheet Thickness (751-900 mm duct)— For low pressure class (≤ 500 Pa). Refer table for other sizes/pressures.
1.00 mm
Table 4
SS Sheet Thickness (751-900 mm duct)— For low pressure class (≤ 500 Pa). Refer table for other sizes/pressures.
0.63 mm
Table 5
Max Transverse Joint Spacing— Corresponds to standard sheet lengths.
2440 mm
Cl. 6.2.1
Stiffener Spacing (451-600 mm duct)— For 0.80 mm sheet. Refer table for other sizes.
1500 mm
Table 7
Max Hanger/Support Spacing
2500 mm
Cl. 7.4.1 (Table 8)
Hanger Rod Diameter (≤ 750 mm duct width)
8 mm
Table 8
Hanger Angle Size (≤ 750 mm duct width)
25 x 25 x 3 mm
Table 8
Max Flexible Duct Length— Should be installed fully extended and with minimum bends.
3 m
Cl. 7.6
Duct Leakage Test Pressure
1.25 × Design Static Pressure
Cl. 8.2.1
Allowable Leakage Formula— L_max in l/s/m²; P in Pa. C_L is leakage coefficient.
L_max = C_L × P^0.65
Cl. 8.2.2 (Table 9)
Leakage Coefficient (Class A - Low Pressure)
0.027
Table 9
Leakage Coefficient (Class B - Medium Pressure)
0.009
Table 9
Leakage Coefficient (Class C - High Pressure)
0.003
Table 9
Thermal Insulation 'k' Value (Max)— At 24°C mean temperature.
0.04 W/m.K
Cl. 4.5.1
⚠ Verify against the latest BIS/IRC publication and project specifications. Amendment Slips may modify values.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Pay close attention to sealing all joints and seams as per Clause 6.6 to minimize air leakage, which is a major source of energy loss.
! Ensure correct duct gauge selection from Table 1 based on duct dimensions and pressure class; using undersized gauges leads to duct flutter and noise.
! Verify that support spacing (Table 11) and type are adequate to prevent sagging over time.
Thermal insulation of pipework, ductwork, associated equipment and other industrial installations in the temperature range of -100 °C to +870 °C. Code of practice
Directly equivalent 'Code of Practice' covering the specification and application of thermal insulation for industrial equipment, pipework, and ductwork. The scope and structure are highly aligned with IS 11210.
ASTM C1696-18ASTM International
HighCurrent
Standard Guide for Industrial Thermal Insulation Systems
Covers similar subject matter including materials, design, installation, and maintenance of industrial insulation. As a 'Guide', it is less prescriptive than the IS 'Specification', but the technical considerations are very similar.
BS 5422:2009BSI (British Standards Institution)
MediumCurrent
Method for specifying thermal insulating materials for pipes, tanks, vessels, ductwork and equipment operating within the temperature range -40°C to +700°C
Focuses specifically on the 'method for specifying' materials, which is a key component of IS 11210. It complements standards like BS 5970 but is less comprehensive on the installation practice itself compared to IS 11210.
ISO 12241:2008ISO (International Organization for Standardization)
LowCurrent
Thermal insulation for building equipment and industrial installations — Calculation rules
This standard is not a direct equivalent for the overall application practice. It is equivalent to the calculation methods (like IS 3346) that IS 11210 references for determining insulation thickness. It only matches a sub-part of the overall scope.
Key Differences
≠IS 11210 is a 'Specification' that provides prescriptive requirements, whereas some international counterparts like ASTM C1696 are 'Guides' that offer recommendations and considerations, allowing more flexibility for the designer.
≠IS 11210 references Indian Standards for material specifications (e.g., IS 8183 for rock wool), testing, and thickness calculation (IS 3346), while international standards reference their respective ecosystems (ASTM, BS, EN, ISO codes).
≠The Indian standard may implicitly or explicitly contain provisions more suited to the Indian climate, such as specific requirements for weatherproofing and vapor barriers in high-humidity and monsoon environments, which may be detailed differently in standards from other regions.
≠While the principles are the same, the specific nominal thicknesses recommended for materials and protective jacketing can vary slightly based on locally available standard commercial sizes and manufacturing practices.
Key Similarities
≈All standards share the fundamental objective of providing a comprehensive framework for selecting, specifying, and installing thermal insulation to achieve energy conservation, personnel protection, process stability, and condensation control.
≈The core installation best practices are consistent across all standards, including the need for proper surface preparation, staggering of joints in multi-layer systems, use of contraction/expansion joints, and securement methods like banding.
≈The requirement for a vapor barrier system on the outer (warm) side of insulation for cold services (operating below ambient temperature) to prevent condensation is a universal principle in all comparable standards.
≈All standards mandate the use of a protective outer covering (jacketing/cladding) to protect the insulation from mechanical damage, weather, and chemical exposure, and provide specifications for its material and installation.
≈The underlying physics and calculation principles for determining required insulation thickness to achieve a target heat loss/gain or surface temperature are the same, even if the referenced calculation standards differ.
Parameter Comparison
Parameter
IS Value
International
Source
Personnel Protection Surface Temperature
Not explicitly defined as a single value, but designs typically target ≤ 60-65°C as per common industrial practice in India.
Should not normally exceed 50°C. A higher temperature up to 60°C may be acceptable in certain locations.
BS 5970:2012
Securing Band Spacing (Straight Pipes)
Maximum 300 mm centres.
Maximum 300 mm centres.
BS 5970:2012
Minimum Metal Jacketing Overlap (Circumferential)
50 mm
50 mm
BS 5970:2012
Minimum Metal Jacketing Overlap (Longitudinal on pipes >150 mm dia)
75 mm
50 mm (Note: BS 5970 recommends 75mm for very large flat surfaces)
BS 5970:2012
Minimum Thickness of Aluminium Jacketing (for pipe dia 150-350 mm)
0.71 mm
0.7 mm
BS 5970:2012
Vapor Barrier Requirement
Required for all insulation systems on cold surfaces operating below ambient temperature.
Required for systems operating at or below the dew point of the ambient air.
BS 5970:2012
Staggering of Insulation Joints
Mandatory for multi-layer applications. Both longitudinal and circumferential joints to be staggered.
Recommended for multi-layer applications to prevent thermal bridges. Both longitudinal and circumferential joints should be offset.
ASTM C1696-18
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
Minimum GI sheet thickness for ducts0.50 mm (26 Gauge)
Maximum static pressure for low-pressure ducts500 Pa
Maximum static pressure for medium-pressure ducts1000 Pa
Maximum static pressure for high-pressure ducts2500 Pa
Maximum hanger spacing for ducts up to 750mm2.5 m
Minimum sealant thickness at joints1 mm
Tables & Referenced Sections
Key Tables
Table 1 - Minimum Sheet Metal Thickness for Rectangular Ducts
Table 2 - Minimum Sheet Metal Thickness for Round Ducts
Table 3 - Transverse Joint Reinforcement
Table 11 - Maximum Spacing of Duct Hangers
Key Clauses
Clause 5 - Materials
Clause 6 - Duct Construction and Supports
Clause 7 - Duct Installation
Clause 10 - Testing
Annex A - Recommended Gauges for Rectangular Ducts