A Guide to BREEAM, Pipe and Duct Insulation: UK Standards and Best Practices

4. A Specifier's Guide to Pipe and Duct Insulation Materials

The choice of insulation material is a critical decision that balances thermal performance, fire safety, moisture resistance, and cost. In the UK, three main types of material dominate the specification for building services applications: phenolic foam, mineral wool, and flexible elastomeric foam.

4.1 Phenolic Foam Insulation  

Phenolic foam is a rigid thermoset insulation with a very high closed-cell content and a fine cell structure. Its defining characteristic is its exceptional thermal performance. With a thermal conductivity (lambda value) as low as 0.025 W/m.K, it is one of the most thermally efficient insulation materials commonly available. This efficiency means that specified thermal performance can be achieved with a thinner layer of insulation compared to other materials, which is a significant advantage in congested service voids or where space is at a premium.

Phenolic insulation is suitable for a wide temperature range, typically from -50 deg C to +110 deg C, making it appropriate for insulating chilled water, cold water, LTHW (low-temperature hot water), and heating pipework. In terms of fire performance, as a thermoset material, it chars rather than melts when exposed to flame. Products for pipe and duct applications typically achieve a Euroclass reaction to fire rating of BL-s1,d0 or B-s1,d0, indicating limited contribution to fire, very low smoke production, and no flaming droplets.

4.2 Mineral Wool Insulation (Stone and Glass Wool)

Mineral wool is a fibrous insulation material manufactured from either molten volcanic rock (stone wool) or recycled glass and sand (glass wool). Its primary advantage is its fire performance. Mineral wool is non-combustible and can withstand temperatures in excess of 1,000 deg C. It typically achieves the highest possible Euroclass reaction to fire classifications of A1 (non-combustible) or A2-s1,d0 (limited combustibility). This makes it the material of choice for applications where fire safety is the highest priority.

In addition to its fire resilience, mineral wool possesses excellent acoustic absorption properties. The fibrous structure is effective at dampening sound and vibration, making it a common specification for insulating ductwork to reduce HVAC system noise. Its typical service temperature range for building services applications is from 0 deg C to 250 deg C.

4.3 Flexible Elastomeric Foam (FEF) Insulation

Flexible elastomeric foam (FEF) is a closed-cell synthetic rubber material, commonly based on nitrile rubber (NBR) or ethylene propylene diene monomer (EPDM). Its key strength is its high resistance to water vapour transmission, which gives it a built-in vapour barrier. This property makes it extremely effective at preventing surface condensation when installed on cold and chilled water lines, thus mitigating the risk of moisture damage and corrosion under insulation (CUI).

As its name suggests, the material is highly flexible, which simplifies installation, particularly around complex arrangements of pipes, valves, and fittings. Its fire performance has improved significantly, with modern FEF products capable of achieving Euroclass ratings of B-s3,d0 or BL-s2,d0, making them suitable for a wide range of commercial applications.

Table 1: Comparative Analysis of Common Insulation Materials

5. Compliance and Specification: UK Regulations and Standards

The specification and installation of pipe and duct insulation in the UK are governed by a framework of legal requirements and technical standards. For any project, particularly one aiming for BREEAM certification, compliance with these is non-negotiable. The two most important documents are Building Regulations Part L and the British Standard BS 5422.

5.1 Building Regulations Part L - Conservation of Fuel and Power

Part L of the UK Building Regulations is a statutory requirement that sets the standards for energy performance and the conservation of fuel and power in buildings. The guidance is split into two volumes: Volume 1: Dwellings and Volume 2: Buildings other than dwellings.

Both volumes mandate that reasonable provision must be made to limit heat gains and losses from pipes, ducts, and vessels. For example, in non-domestic buildings, the guidance in Approved Document L, Volume 2 states that hot water pipework must be insulated both inside and outside the building unless the heat loss from it can be demonstrated as "always useful". It provides indicative tables for minimum insulation thicknesses based on pipe diameter and the thermal conductivity of the insulation material used. These regulations form the legal baseline for performance that all projects must meet.

5.2 BS 5422:2023 - The Method for Specification

BS 5422 is the key British Standard that provides the technical methodology for specifying thermal insulation for pipes, ducts, and equipment. It is the primary reference document used to demonstrate compliance with the requirements of Building Regulations Part L. The standard's purpose is to provide guidance on determining the appropriate insulation thickness needed to achieve specific objectives, such as conserving energy by controlling heat loss or gain, controlling surface condensation, preventing the freezing of pipe contents, and protecting personnel from hot surfaces.

To use the standard, a specifier must consult a series of tables. The correct table and required thickness are determined by several key parameters: the system type (e.g., heating, chilled water), the pipe or duct size, the system operating temperature, the ambient temperature, the emissivity of the outer surface, and the thermal conductivity (lambda value) of the chosen insulation product.

The 2023 revision of BS 5422 introduced several important changes. National fire classifications (like Class 0) were replaced with the European Euroclass system, and the tables were simplified. A significant change was the introduction of 'base' and 'enhanced' performance tables for energy conservation, with the more stringent 'enhanced' levels often presented as the default option for specifiers to consider.

The practical outcome of this standard is that a material with a lower thermal conductivity (better thermal performance) will require a smaller thickness to meet the same heat loss or gain limit as a material with a higher thermal conductivity. This relationship directly impacts design decisions, especially concerning space allocation for building services.

Table 2: Illustrative Insulation Thickness Comparison (BS 5422:2023, Table 15a)

This table illustrates how the choice of material affects the required thickness for a non-domestic heating service pipe (steel, 42.4 mm OD) to meet the base level heat loss limit of 12.30 W/m.

Note: Thicknesses are indicative and derived from manufacturer data aligned with BS 5422:2023 tables. Always consult the full standard and manufacturer's specific literature for precise calculations.

5.3 BS 5970 - The Code of Practice for Installation

While BS 5422 deals with what to specify, BS 5970:2012 is the code of practice that details how to install it. It covers essential aspects of workmanship, including surface preparation, the correct methods for fixing and securing insulation, sealing joints, and applying protective finishes. Adherence to BS 5970 is critical to ensure that the specified insulation system performs as designed.

6. Best Practices for High-Performance Insulation Installation 

The theoretical performance of a high-quality insulation material can be completely undermined by poor installation. The integrity of the entire insulation system depends on meticulous attention to detail during application. A system is only as effective as its weakest point, and common failures at joints, fittings, and supports can lead to significant energy loss and condensation problems.

Surface preparation is the first step. Before any insulation is applied, the surface of the pipe or duct must be clean, dry, and free of any dust, oil, or scale. Contaminants can compromise the adhesion of tapes and adhesives and prevent the insulation from fitting snugly.

Next is ensuring a snug fit. The insulation sections must fit tightly around the pipe or duct, with no air gaps between the insulation and the surface. For flexible tube insulation, the material should be pushed onto the pipe, not stretched or pulled, as this can reduce its wall thickness and compromise performance. When installing sections on horizontal pipework, the longitudinal slit or joint should be positioned to the side (e.g., at the 3 or 9 o'clock position), not at the top where it might be affected by heat or at the bottom where it could collect moisture.

Sealing all joints is arguably the most critical step. Every joint, both longitudinal (along the length of the section) and circumferential (where two sections meet), must be completely sealed. For foil-faced products, a matching self-adhesive aluminium foil tape should be used to create a continuous thermal and vapour barrier. For non-faced products like some elastomeric foams, a compatible adhesive must be applied to both surfaces before they are joined. Any gap represents a path for heat transfer and, on cold systems, a point for condensation to form.

Insulating fittings and bends is also crucial. Pipe fittings such as elbows, tees, and valves must be insulated to the same thickness and standard as the main pipe run. This is typically achieved by fabricating insulation covers from sections of the same material. For a 90° bend, this involves cutting two pipe sections at a 45° angle to form a mitred joint, ensuring a continuous and uniform layer of insulation around the corner.

A common and serious installation error is failing to prevent thermal bridging at supports. Allowing the pipe to rest directly on a metal support bracket, with the insulation simply cut away around it, creates a thermal bridge, a direct path for heat to bypass the insulation. The correct practice, as outlined in standards like BS 5422, is to use load-bearing insulated pipe supports. These are high-density blocks of a compatible insulation material (e.g., high-density phenolic or stone wool) that sit between the pipe and the bracket, ensuring the continuity of the thermal insulation and vapour barrier across the support point.

Finally, applying protective finishes is necessary in certain locations. In areas where the insulation is exposed to weather, UV radiation, or potential mechanical damage (such as in plant rooms or outdoors), it must be protected by a suitable cladding or jacketing system.

7. The Wider Sustainability Context: Recycled Content and End-of-Life 

A truly holistic assessment of a material's sustainability extends beyond its operational performance to consider its composition and what happens at the end of its service life. For insulation, this involves looking at recycled content and the practicalities of recycling.

7.1 Recycled Content

The use of recycled materials in manufacturing reduces the need for virgin raw materials, often saving significant energy and reducing the environmental impact of extraction.

Mineral wool is a strong performer in terms of recycled content. Glass mineral wool can contain up to 80% recycled glass, sourced from post-consumer glass bottles and manufacturing offcuts. Stone wool is manufactured from naturally abundant volcanic rock but also incorporates recycled material, such as slag from the steel industry and production waste, which can constitute around 35% of the final product.

For phenolic foam, as a product of a specific chemical reaction, it does not contain post-consumer recycled content in the same way as mineral wool. However, some manufacturers are able to reintroduce production waste and offcuts back into the manufacturing process, reducing overall waste. Furthermore, active research is underway, in partnership with industry, to develop viable chemical recycling processes that could break down old foam into its constituent parts for reuse, aiming to create a circular economy for these materials in the future.

7.2 Recyclability and End-of-Life

The distinction between a material being "recyclable" and it being widely "recycled" is a critical one. The existence of a practical and economically viable infrastructure for collection and reprocessing is key.

For mineral wool, in theory, it is completely recyclable and can be melted down to create new insulation products. Some manufacturers in the UK operate take-back schemes for clean, uncontaminated site offcuts. However, recycling insulation from demolition sites is more challenging due to potential contamination, and much of it still ends up in landfill.

Foams (phenolic and elastomeric) present greater recycling challenges. While chemical or mechanical recycling methods exist, they are not widely established at a commercial scale in the UK. The primary barriers are logistical; foam is lightweight and bulky, making it expensive to transport, and it is often contaminated with adhesives, tapes, or building debris. Consequently, for most foam insulation products at the end of their life, landfill or energy-from-waste incineration are the most common disposal routes.

This reality means that while specifying products for their recyclability is a forward-thinking goal, specifying products with high recycled content is currently a more direct and verifiable way to contribute to the circular economy.

8. Conclusion

The effective insulation of pipework and ductwork is an indispensable element of sustainable building design and a key contributor to achieving high BREEAM ratings. It moves beyond being a simple compliance exercise and becomes a strategic tool for architects, specifiers, and engineers. The selection of the right insulation material, specified to the correct thickness according to UK standards and installed with meticulous attention to detail, delivers a cascade of benefits that align directly with BREEAM's core objectives.

By reducing the energy demand of a building's mechanical services, high-performance insulation directly lowers operational costs and carbon emissions, satisfying the primary goals of the Energy category. By choosing products with favourable life cycle assessments and from manufacturers with certified environmental management systems, project teams can secure valuable credits in the Materials category. Furthermore, the specification of low-VOC and acoustically absorbent insulation directly creates a healthier and more comfortable indoor environment for occupants, a central tenet of the Health and Wellbeing category.

Ultimately, the integration of high-performance technical insulation into a project's design is a clear indicator of a comprehensive approach to sustainability. It reflects an understanding that true building performance is the sum of all its parts, and that even components within service voids play a vital role in delivering buildings that are not only environmentally responsible but also economically efficient and beneficial for the people who use them.

Legal Disclaimer

The information contained in this article is for general guidance and informational purposes only. It is not intended to be a substitute for professional advice. The content should not be used as a basis for specification or other decisions without consulting the relevant and current British Standards, manufacturer's technical data sheets, and seeking advice from suitably qualified professionals, such as architects, engineers, or BREEAM assessors. While every effort has been made to ensure the accuracy and completeness of the information provided, the author and publisher assume no responsibility or liability for any errors or omissions, or for any loss or damage of any kind arising from the use of, or reliance on, this content. All specifications and applications should be verified with the product manufacturer.