Armaflex Pipe Insulation
Armaflex Pipe Insulation — The Professional's Choice for Pipe Lagging
Armaflex is the world's leading flexible elastomeric pipe insulation, manufactured by Armacell and specified by engineers, contractors and building services professionals across the UK. Whether you're insulating domestic hot and cold water pipes, commercial HVAC systems, refrigeration pipework or condensate lines, Armaflex delivers proven thermal performance, condensation control and long-term durability. Read our complete pipe insulation guide if you're not sure where to start.
What is Armaflex?
Armaflex is a closed-cell, flexible foam pipe insulation made from elastomeric rubber. Its closed-cell structure gives it an exceptionally low water vapour permeability, which is what makes it the preferred choice for condensation control on chilled water and refrigeration pipework. Unlike open-cell foam, moisture cannot penetrate the insulation and cause corrosion or mould growth on the pipe surface beneath. See our condensation on pipes guide for more detail.
Why engineers specify Armaflex
- Class O fire rating — meets the highest surface spread of flame classification for use in commercial and public buildings. Understand BS 476 fire ratings.
- Condensation control — closed-cell structure prevents moisture ingress on cold pipework
- Energy efficiency — reduces heat loss on hot water systems and heat gain on chilled water systems. See how much energy pipe insulation saves.
- Flexibility — wraps around bends, valves and fittings without specialist tools. Read our Armaflex pipe bend guide.
- Durability — UV-stable grades available for outdoor installation
- Wide temperature range — suitable from -200°C to +150°C depending on grade
Armaflex Applications
HVAC and Building Services: Armaflex is the standard specification for chilled water pipework, air handling units and fan coil unit connections in commercial buildings. Its Class O rating satisfies building regulations for exposed pipework in occupied spaces. Read our guide to choosing pipe insulation for HVAC systems.
Domestic Plumbing: Use Armaflex on hot and cold water pipes to prevent heat loss, reduce the risk of freezing and comply with Part L of the Building Regulations. See our hot water pipe insulation guide for Part L compliance advice.
Refrigeration: Armaflex is widely used on refrigerant pipework in air conditioning and refrigeration systems where condensation control is critical.
Condensate Pipes: Boiler condensate pipes running externally are vulnerable to freezing. Armaflex provides reliable frost protection for exposed condensate lines. Read our guide on using Armaflex to prevent frozen pipes.
Outdoor and Underground: For exposed external pipework, see our Armaflex Tuffcoat underground insulation guide and our best outdoor pipe insulation guide.
Armaflex Pipe Size Guide
Not sure which size you need? Read our how to measure pipe insulation guide or our copper pipe size vs insulation size guide.
| Pipe Size | Common Application | Typical Wall Thickness |
|---|---|---|
| 15mm | Domestic hot & cold water, condensate pipes | 13mm or 19mm |
| 22mm | Central heating flow and return | 13mm or 19mm |
| 28mm | Larger heating systems, primary circuits | 19mm or 25mm |
| 35mm | Commercial heating and chilled water | 19mm or 25mm |
| 42mm | Commercial HVAC pipework | 25mm or 32mm |
| 54mm | Large commercial systems | 25mm or 32mm |
| 76mm+ | Industrial and district heating | 32mm+ |
Choosing the Right Armaflex Wall Thickness
Wall thickness selection depends on the pipe temperature, ambient conditions and whether you need to comply with Building Regulations Part L. Read our detailed Armaflex thickness guide or our complete pipe insulation thickness guide for full guidance including BS 5422 compliance. As a general rule: 13mm wall is suitable for domestic hot water pipes in heated spaces; 19mm wall is recommended for pipes in unheated spaces or where greater energy savings are required; 25mm and above is typically specified for chilled water and refrigeration pipework where condensation control is the primary concern.
Armaflex Grades Available
- Armaflex Class O — standard grade, Class O fire rated, suitable for most HVAC and plumbing applications. Read the Armaflex Class O technical guide.
- Armaflex Self Seal — factory-applied adhesive on the longitudinal seam for faster installation
- Armaflex EVO — next-generation formula with improved environmental credentials. Read the Armaflex EVO guide.
- Armaflex HT Solar — high-temperature grade for solar thermal systems up to 150°C
- Armaflex Ultima — premium grade with enhanced fire performance
- Armaflex Rail — specified for rail and transport applications
- NH Armaflex Smart — ammonia-resistant grade for industrial refrigeration
- Armaflex Sheet Insulation — flexible sheet for wrapping irregular shapes, valves and fittings
Frequently Asked Questions
Is Armaflex waterproof?
Yes. Armaflex has a closed-cell structure which gives it very low water vapour permeability. It is highly resistant to moisture ingress, making it suitable for condensation control on chilled water and refrigeration pipework. Read more in our waterproof pipe lagging guide.
Can Armaflex be used outdoors?
Standard Armaflex is not UV-stable and will degrade if left exposed to sunlight. For outdoor installations, use Armaflex with an appropriate outdoor finish, protective coating or jacketing. Armaflex HT Solar is designed for outdoor solar thermal applications. See our Tuffcoat outdoor pipe insulation guide for exposed external pipework.
What is Class O insulation?
Class O is the highest classification for surface spread of flame under BS 476. It means the material will not significantly contribute to the spread of fire across its surface. Armaflex Class O is required in many commercial and public building applications. Read our full guide to insulation fire ratings.
What size Armaflex do I need for 15mm copper pipe?
You need Armaflex with a 15mm bore (internal diameter). The wall thickness you choose depends on the application — 13mm wall for standard domestic hot water, 19mm for unheated spaces or Part L compliance. Read our 15mm pipe insulation guide or browse 15mm pipe insulation.
Does Armaflex prevent condensation?
Yes. The closed-cell structure of Armaflex prevents water vapour from reaching the cold pipe surface, which is what causes condensation. This is why it is the standard specification for chilled water and refrigeration pipework. Read our condensation on pipes guide.
What is the difference between Armaflex and Tubolit?
Both are elastomeric pipe insulation products made by Armacell. Armaflex is the premium grade with Class O fire rating and is specified for commercial and HVAC applications. Tubolit is a more economical grade suited to domestic plumbing and heating. Read our full Armaflex vs Tubolit comparison guide.
How do I measure pipe insulation size?
Pipe insulation is sized by the outside diameter of the pipe, not the bore. Measure the outside diameter of your pipe and match it to the bore size of the insulation. For standard copper pipe: 15mm OD = 15mm bore insulation, 22mm OD = 22mm bore insulation. Read our full pipe insulation sizing guide.
Armaflex Comparisons
Compare Armaflex against other leading insulation products:
Need Help Choosing Armaflex?
Not sure which Armaflex pipe insulation you need? Our technical team can help you choose the correct pipe size, wall thickness and insulation grade for your project. Call us on 0161 775 1190 for expert advice.
