Armaflex vs Rockwool Pipe Insulation — Which Should You Choose?

June 7, 2026

What Is Armaflex Pipe Insulation?

Armaflex EVO is a flexible closed-cell elastomeric foam insulation manufactured by Armacell, designed for heating, chilled water, refrigeration and HVAC pipework. Its integrated vapour barrier (μ ≥ 10,000) makes it one of the most effective solutions for preventing condensation on cold pipework — a property no other standard pipe insulation material can match without additional vapour barrier treatment.

It is widely specified across commercial and domestic applications where condensation control, thermal performance and ease of installation are the primary requirements. Available in standard (open slit) and self-seal versions, Armaflex EVO fits pipework from 6mm to 160mm OD in wall thicknesses from 6mm to 32mm.

Shop Armaflex EVO · Armaflex EVO Guide

What Is Rockwool Pipe Insulation?

Rockwool Rocklap is a mineral wool pipe insulation manufactured from non-combustible stone wool fibres. It is supplied as rigid pre-formed pipe sections with a reinforced aluminium foil facing in 1m lengths. Rockwool is A1 non-combustible (Euroclass A1) and rated to 750°C continuous operating temperature — making it the only standard pipe insulation material suitable for steam pipework and high-temperature industrial applications.

Rockwool is commonly specified on commercial heating systems, steam pipework and fire-rated applications where high temperature resistance and non-combustibility are required.

Shop Rockwool Rocklap · Rockwool Guide

Armaflex vs Rockwool — Quick Comparison

Property	Armaflex EVO	Rockwool Rocklap
Thermal conductivity	λ = 0.033 W/mK	λ = 0.034–0.040 W/mK
Max operating temperature	+105°C	+750°C
Fire rating	Class O, B-s2,d0	A1 non-combustible
Vapour barrier	Built-in (μ ≥ 10,000)	None
Condensation control	Yes — closed cell	No — open fibre
Flexibility	Flexible, easy to fit	Rigid sections, 1m lengths
Best for	HVAC, heating, chilled water	Steam, high temp, fire-rated

Fire Rating: Armaflex vs Rockwool

Fire performance is one of the biggest differences between these two materials.

Rockwool Rocklap achieves Euroclass A1 non-combustible status — the highest fire classification available. A1 means the material will not contribute to fire growth under any circumstances. It is the standard specification for fire-rated pipework penetrations, compartmentation and any application where non-combustible insulation is required by the specification or building regulations.

Armaflex EVO achieves Euroclass B-s2,d0 and Class O (BS 476 Part 6 & 7). While this represents excellent fire performance for an HVAC insulation material — and satisfies the vast majority of commercial HVAC specifications — it is not non-combustible and cannot be specified where A1 is required.

Where a specification requires A1 or non-combustible insulation, Rockwool Rocklap is the correct choice.

Condensation Control: Which Material Performs Better?

For chilled water and refrigeration systems, Armaflex EVO is the clear winner — and there is no close second.

Armaflex EVO's closed-cell structure and integrated vapour barrier (μ ≥ 10,000) prevent moisture ingress and condensation formation on cold pipework. When all joints and seams are fully sealed with Armaflex 520 adhesive, the insulation system forms a continuous vapour barrier around the pipe, keeping the pipe surface above the dew point temperature and preventing condensation entirely.

Rockwool Rocklap does not provide a vapour barrier. Its open mineral fibre structure will absorb moisture if exposed to humid air on cold pipework. For condensation-critical applications, Rockwool requires additional protective vapour barrier layers. For any condensation-critical application, Armaflex EVO is the recommended choice.

Temperature Range: Armaflex vs Rockwool

Armaflex EVO — -50°C to +105°C. Suitable for the vast majority of domestic and commercial heating, HVAC and chilled water applications. Not suitable for steam or high-temperature industrial pipework above +105°C
Rockwool Rocklap — up to +750°C continuous. The only standard pipe insulation material suitable for steam pipework, high-temperature heating mains above 120°C and industrial process pipework at elevated temperatures

When to Choose Armaflex EVO

Chilled water and condensation control — the only standard pipe insulation with a built-in vapour barrier
Heating and HVAC up to +105°C — LTHW, MTHW, domestic hot water and commercial HVAC pipework
Complex pipework — flexible foam is easier to fit on pipework with many bends, valves and fittings
Refrigeration pipework — rated to -50°C, suitable for refrigerant lines and cold store pipework
Acoustic attenuation — elastomeric foam provides good noise reduction on plumbing and HVAC pipework

When to Choose Rockwool Rocklap

Steam pipework and high-temperature applications above +105°C — the only standard option rated to 750°C
Fire-rated applications — A1 non-combustible, specified for fire-rated pipework penetrations and compartmentation
Commercial and industrial heating mains — standard specification for high-temperature MTHW and steam distribution
Where non-combustibility is specified — any application requiring A1 or non-combustible insulation classification

Frequently Asked Questions

Is Armaflex better than Rockwool?

It depends on the application. For chilled water, condensation control and standard HVAC heating up to +105°C, Armaflex EVO is generally the better choice. For high-temperature applications above +105°C, steam pipework and fire-rated applications requiring A1 non-combustible insulation, Rockwool Rocklap is the correct specification.

Can Rockwool be used on chilled water pipes?

It can, but additional vapour barrier protection is normally required. Rockwool's open mineral fibre structure does not prevent condensation on cold pipework. For condensation-critical chilled water applications, Armaflex EVO is the preferred and simpler specification.

Which insulation has the best fire rating?

Rockwool Rocklap achieves Euroclass A1 non-combustible status — the highest fire classification available. Armaflex EVO achieves Class O and B-s2,d0, which satisfies most commercial HVAC specifications but is not non-combustible.

Which insulation is best for preventing condensation?

Armaflex EVO is specifically designed for condensation control and is the preferred choice for all condensation-critical applications. Its closed-cell structure and built-in vapour barrier (μ ≥ 10,000) prevent moisture reaching the pipe surface when all joints are properly sealed.

Can I use Armaflex on steam pipes?

No. Armaflex EVO is rated to a maximum of +105°C. Steam pipework operates above this temperature and requires mineral wool insulation such as Rockwool Rocklap, which is rated to 750°C continuous.

Which is easier to install?

Armaflex EVO is generally easier to install, particularly on complex pipework with many bends and fittings. Its flexibility allows it to follow pipe contours without cutting. Rockwool Rocklap is supplied in rigid 1m sections and requires mitred cuts for bends.

Conclusion

Armaflex EVO and Rockwool Rocklap are designed for very different applications. Armaflex EVO is the preferred choice for chilled water, refrigeration, HVAC and condensation-critical systems thanks to its closed-cell structure and integrated vapour barrier. Rockwool Rocklap is the correct specification for steam pipework, high-temperature systems and applications requiring A1 non-combustible insulation.

For most commercial HVAC and heating systems up to +105°C, Armaflex EVO offers the best combination of thermal performance, flexibility and condensation protection. For temperatures above +105°C or where fire performance is the primary requirement, Rockwool Rocklap remains the industry standard.