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).

IS 13666

: 1993

Design and installation of thermal insulation for refrigeration and air conditioning systems - Code of practice

CurrentFrequently UsedCode of PracticeBIMMEP · Insulation Materials

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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.

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)

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).