Armaflex pipe insulation is available in two formats: standard solid tube (sometimes called "unslit") and self-seal (pre-slit with a factory-applied adhesive closure). Both use the same Armaflex EVO closed-cell nitrile rubber foam and offer identical thermal, vapour barrier and fire performance — the difference is purely in the format and how they are installed.
This guide explains when to use each format, the installation speed and cost trade-offs, and the applications where one format is clearly preferable to the other.
What Is the Difference Between Armaflex Self-Seal and Standard?
Armaflex Standard (Solid Tube)
Armaflex EVO standard pipe insulation is supplied as a solid, unslit tube. To install it on existing pipework, the tube must be cut along its length with a sharp knife, opened around the pipe, and the longitudinal seam bonded with Armaflex 520 adhesive. On new pipework that has not yet been connected, standard tube can be slid onto the pipe without cutting.
Key characteristics:
- Unslit — must be cut and bonded on existing pipework
- Requires Armaflex 520 adhesive for seam closure
- Slightly lower cost per metre than self-seal
- Preferred for new installations where pipe is not yet connected
- Better for long straight runs where speed of adhesive application is not a limiting factor
- Available in the widest range of bore sizes and wall thicknesses
Armaflex Self-Seal
Armaflex EVO self-seal pipe insulation is supplied pre-slit along its length with a factory-applied pressure-sensitive adhesive strip on the seam. To install, simply open the insulation around the pipe and press the seam closed — no separate adhesive required for the longitudinal seam. Butt joints between sections still require Armaflex 520 adhesive.
Key characteristics:
- Pre-slit with factory adhesive closure — no adhesive needed for the longitudinal seam
- Significantly faster to install on existing pipework
- Higher cost per metre than standard tube
- Ideal for retrofit and maintenance work on existing pipework
- Reduces adhesive usage and associated solvent exposure on site
- Available in the most common bore sizes and wall thicknesses — range is slightly narrower than standard
Performance — Is There Any Difference?
No. Both formats use identical Armaflex EVO foam with the same thermal conductivity (λ ≤ 0.033 W/mK), vapour resistance (μ ≥ 10,000), Microban antimicrobial protection and Class O fire rating. The self-seal adhesive strip, when correctly pressed closed, provides an equivalent seam bond to a correctly applied Armaflex 520 adhesive joint.
The only performance caveat is installation quality — a self-seal seam that has not been firmly pressed along its full length, or that has been contaminated with dust or moisture before closure, will not bond correctly. The same applies to a poorly applied adhesive seam on standard tube. In both cases, correct installation technique is the determining factor.
When to Use Armaflex Self-Seal
- Retrofit and maintenance work — replacing or adding insulation to existing connected pipework where sliding standard tube onto the pipe is not possible
- High-volume installations — where installation speed is critical and the cost premium is justified by labour savings
- Confined spaces — where applying adhesive is difficult or impractical
- Reducing solvent exposure — self-seal eliminates the need for adhesive on the longitudinal seam, reducing VOC exposure for installers working in enclosed spaces
- Domestic plumbing and heating — fast, clean installation on standard 15mm and 22mm copper pipework
When to Use Armaflex Standard Tube
- New installations — where pipework has not yet been connected and standard tube can be slid onto the pipe without cutting
- Cost-sensitive projects — standard tube is cheaper per metre; on large commercial projects the saving is significant
- Non-standard bore sizes — standard tube is available in a wider range of bore sizes, including larger diameters not available in self-seal format
- Non-standard wall thicknesses — thicker wall sections (32mm, 40mm) are generally only available in standard tube format
- Chilled water and refrigeration — where a fully bonded seam with Armaflex 520 adhesive is specified for maximum vapour barrier integrity
Cost Comparison
Armaflex self-seal typically carries a 15–25% price premium over equivalent standard tube. On a small domestic job — insulating a boiler and a few metres of pipework — the premium is negligible and the time saving is worthwhile. On a large commercial project with hundreds of metres of pipework, the cost difference is significant and standard tube with adhesive is generally the more economical specification.
The labour saving from self-seal is most significant on retrofit work where every section must be cut and fitted around existing pipework. On new installations where standard tube can be slid on before connections are made, the installation speed difference is minimal.
Do I Still Need Adhesive with Self-Seal?
Yes — for butt joints between sections. The self-seal adhesive strip only closes the longitudinal seam. All butt joints (the cut ends where two sections meet) must still be bonded with Armaflex 520 adhesive to maintain the vapour barrier. On a typical installation, butt joints occur every 2 metres — so adhesive is still required on site, just in smaller quantities than for standard tube.
Quick Reference — Which Format to Choose
- New pipework, not yet connected: Standard tube — slide on before connecting
- Existing connected pipework, retrofit: Self-seal — faster, no adhesive on seam
- Large commercial project, cost-sensitive: Standard tube — lower material cost
- Small domestic job, speed priority: Self-seal — faster installation
- Non-standard bore or thick wall: Standard tube — wider range available
- Confined space, limited ventilation: Self-seal — reduces solvent exposure
Products
- Armaflex EVO Standard Pipe Insulation — solid tube, full range of bore sizes and wall thicknesses
- Armaflex EVO Self-Seal Pipe Insulation — pre-slit with factory adhesive closure
- Armaflex 520 Adhesive — required for butt joints on both formats, and seam bonding on standard tube
Frequently Asked Questions
Is self-seal Armaflex as good as standard?
Yes — identical foam, identical performance. The self-seal adhesive strip provides an equivalent seam bond to correctly applied Armaflex 520 adhesive. The difference is installation method only.
Can I use self-seal on chilled water pipework?
Yes. Self-seal Armaflex EVO has the same vapour resistance (μ ≥ 10,000) as standard tube. Ensure the seam is firmly pressed along its full length and all butt joints are bonded with Armaflex 520 adhesive.
Do I need adhesive at all with self-seal?
You still need Armaflex 520 adhesive for butt joints between sections. The self-seal strip only closes the longitudinal seam — it does not replace adhesive at cut ends.
Is self-seal available in all sizes?
Self-seal is available in the most common bore sizes (13mm to 54mm) and wall thicknesses (9mm, 13mm, 19mm, 25mm). For larger bore sizes or thicker walls (32mm+), standard tube is the correct format.
Can I use standard tube on existing pipework?
Yes — cut along the length with a sharp knife, open around the pipe, and bond the seam with Armaflex 520 adhesive. Self-seal is faster for this application but standard tube works equally well when correctly installed.
For advice on the correct Armaflex format for your application, call our team on 0161 775 1190 (Mon–Fri 8am–4pm) or browse the full Armaflex range.
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