Class O Pipe Insulation & Self-Seal Tubes
Class O pipe insulation is widely used across HVAC, refrigeration, heating and chilled-water systems to improve energy efficiency, reduce heat loss, prevent condensation and help protect pipework from freezing. The BES range includes both straight Class O insulation tubes and easy-fit self-seal variants, giving installers options for everything from new pipework runs to quick retrofitting in plant rooms, roof spaces or service voids.
With fast delivery options, free shipping over £50 and straightforward online ordering, BES makes it easy to source insulation alongside the rest of your HVAC components.
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Class O Insulation & Self-Seal Tube Options At BES
With a variety of tube sizes, wall thicknesses and installation formats available, the Class O range at BES supports everything from short pipe runs to large HVAC distribution routes. Installers can choose between long-length Kaiflex ST coils for continuous insulation, straight tubes for precise sectioning, and self-seal variants for fast, reliable fitting in tight or awkward spaces. Accessories, such as Class O adhesive tape, complete the system and help maintain a continuous vapour barrier at joints and fittings.
Class O Insulation Tubes
At BES, we offer a full range of Class O Insulation Tube sizes, including 3/8" x 9 mm x 2 m, 1.1/8" (28 mm) x 13 mm x 2 m, 1.3/8" (35 mm) x 25 mm x 2 m, 1.5/8" (42 mm) x 25 mm x 2 m, and 2.1/8" (54 mm) x 9 mm or 25 mm x 2 m, covering everything from refrigeration lines to large-bore chilled-water pipework. These tubes are used across hot water, cold water, HVAC and refrigeration systems where maintaining thermal stability is important.
Kaiflex ST Class O Coils
Kaiflex ST Class O coils offer long-length insulation ideal for uninterrupted pipe runs. Sizes include Kaiflex 7/8" (22 mm) x 13 mm x 14 m, and 1.1/8" (28 mm) x 9 mm x 14 m, as well as smaller refrigeration sizes such as 1/4" x 13 mm x 26 m.
Self-Seal Tubes
Self-seal tubes feature a pre-applied adhesive edge that allows quick installation without additional tools or tapes. This makes them ideal for retrofitting in tight spaces, refurbishments or time-critical service work. Sizes include: 5/8" (15 mm) x 13 mm x 2 m, 7/8" (22 mm) x 13 mm or 9 mm x 2 m, 1.1/8" (28 mm) x 13 mm or 9 mm x 2 m, 1.3/8" (35 mm) x 13 mm or 9 mm x 2 m, 1.5/8" (42 mm) x 13 mm or 9 mm x 2 m and 2.1/8" (54 mm) x 13 mm or 9 mm x 2 m.
What Is Class O Insulation
Class O insulation is a flexible, closed-cell elastomeric material designed to limit heat transfer, control surface condensation and provide reliable moisture resistance on pipework. Its structure delivers a high vapour-diffusion resistance, helping prevent moisture tracking through the insulation, a key requirement on chilled-water and refrigeration lines. With a thermal conductivity of around ≤ 0.034 W/(m·K) and an operating temperature range of approximately –50 °C to +110 °C, Class O insulation is suitable for hot and cold water services, heating systems, HVAC pipework and refrigeration applications.
Available in both straight tubes and long-length coils, and compatible with standard metric copper pipe sizes, Class O insulation provides installers with a practical, high-performance solution for energy conservation and condensation control across a wide range of building services.
Choosing The Right Class O Insulation
Selecting suitable insulation depends on pipe diameter, operating temperature and the level of vapour control required. Thicker insulation generally provides better thermal performance and may be preferred on chilled-water and refrigeration lines where condensation is a greater risk. For long, uninterrupted runs, coils minimise joints and simplify installation, while self-seal tubes are ideal for quick fitting or retrofit projects.
For metric copper tube, equivalent imperial sizes apply; for example, 15 mm ≈ 5/8", 22 mm ≈ 7/8", and 28 mm ≈ 1.1/8", helping ensure compatibility across HVAC and refrigeration applications.
Technical Specifications Overview
Most Class O insulation in this category is designed to meet common performance requirements:
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Thermal conductivity: ≤ 0.034 W/(m·K) at typical testing conditions
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Water vapour diffusion resistance: μ ≥ 10,000 (closed-cell vapour barrier)
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Operating temperature range: approx. –50 °C to +110 °C (check product pages for exact limits)
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Fire performance: Class O designation (when tested to relevant standards); many tubes carry Euroclass BL-s3,d0
Always refer to individual product listings for precise technical data.
How To Install Class O & Self-Seal Insulation
Class O insulation should fit snugly around the pipe with all seams sealed to maintain the vapour barrier. For straight tubes, installers typically cut the insulation cleanly with a sharp knife and seal longitudinal joints using an approved tape such as Class O Adhesive Tape (Black).
Self-seal insulation simplifies installation: the tube is opened along the split, positioned around the pipe and pressed closed along the adhesive strip. Consistent pressure ensures a proper seal, particularly on chilled-water or refrigeration lines where vapour integrity is critical. All elbows, tees and terminations should be taped or mitred carefully to avoid gaps.
Where insulation is installed outdoors, a weather-resistant outer covering may be required depending on exposure.
Why Shop At BES
We supply Class O insulation with the working installer in mind, products chosen for consistent sizing, reliable thermal performance and straightforward installation. Our range includes coils, straight tubes and self-seal options to suit everything from commercial HVAC pipework to domestic heating and chilled-water systems.
With rapid dispatch, free delivery over £50 and a 30-day returns policy, BES makes it easy to source insulation alongside the rest of your air-conditioning and refrigeration components.
Here To Help
If you’re unsure which insulation thickness or format best suits your system, our technical team can advise on product selection, vapour-barrier considerations and installation approaches. We’re here to support both routine maintenance and larger HVAC projects.
FAQs
What is Class O pipe insulation used for?
Class O insulation is used on hot and cold water services, chilled-water lines, air-conditioning pipework and refrigeration systems. It reduces heat loss, prevents condensation and helps protect pipes from freezing.
What does “Class O” fire rating mean?
Class O refers to the fire performance classification under UK Building Regulations for materials that meet specific surface spread-of-flame and fire-propagation requirements. Many products also carry Euroclass ratings; always check individual product listings for exact compliance details.
How do I install self-seal insulation tubes?
Self-seal tubes have an adhesive strip integrated along the seam. Open the tube, position it around the pipe, then press the seam together firmly along the full length. Seal any joints or fittings using Class O adhesive tape to maintain a continuous vapour barrier.
What are the technical specifications for Class O insulation?
Most Class O products have thermal conductivity ≤ 0.034 W/(m·K), a water vapour resistance of μ ≥ 10,000 and an operating range of approximately –50 °C to +110 °C. Check product pages for precise performance data.
Is this insulation suitable for refrigeration and chilled-water systems?
Yes. Class O insulation is commonly used on refrigeration lines and chilled-water pipework due to its high vapour resistance and reliable condensation control.
Can I use Class O insulation outdoors?
The insulation itself can be used outdoors, but exposed areas may require a weather-resistant covering to protect against UV and mechanical damage.
What is the difference between Class O and Armaflex?
Class O is a performance classification, not a brand. Armaflex is a manufacturer of elastomeric insulation with similar properties. BES supplies Kaiflex ST Class O products, which meet common HVAC and refrigeration requirements.
What diameter pipes will these tubes fit?
Sizes are available from 3/8" up to 2.1/8" (suitable for metric copper tube equivalents such as 10 mm, 15 mm, 22 mm, 28 mm, 35 mm, 42 mm and 54 mm). Individual product listings show exact pipe compatibility.
How reliable is the adhesive on self-seal tubes?
When applied correctly and pressed firmly along the full seam length, the adhesive provides a secure closure suitable for chilled-water and refrigeration systems. All seams and joints should be sealed with approved tape for best results.