Passive Purple Internal airtight membrane between steel frame on a high-rise construction

Airtight and Vapour Control for High-Rise Re-Cladding — Installed From the Outside I

Passive Purple X or Passive Purple + Fred


The High-Rise Re-Cladding Challenge

Modern high-rise re-cladding projects are under intense scrutiny. Fire performance, airtightness, vapour control, and long-term durability are no longer “nice to have”; they’re mandatory.

On many remediation and retrofit schemes, internal access is limited or impossible. Occupied buildings, phased works, and fire-strategy constraints often mean that airtightness and vapour control must be installed from the outside in.

This is exactly where Passive Purple X and Passive Purple + Fred excel.

Why Outside-In Airtightness Matters on High-Rise Projects

Traditional internal vapour control layers (VCLs) are often unrealistic in tall buildings because:

  • Flats remain occupied

  • Internal finishes can’t be removed

  • Fire compartmentation must remain intact

  • Access restrictions limit working hours

Yet airtightness failures in high-rise buildings lead to:

  • Uncontrolled air leakage

  • Interstitial condensation

  • Reduced thermal performance

  • Increased fire and smoke spread risk

External airtight layers solve this if they are vapour-open, durable, and fire-rated.

Option 1: Passive Purple X

The External Airtight & Vapour Control Layer




Key Benefits for High-Rise Re-Cladding:

  • Airtight from the outside in

  • Vapour-open - allows moisture to escape safely

  • Fire Class B - suitable for high-risk façades

  • Liquid-applied - no weak points, laps, or fixings

  • Compatible with mineral wool, timber frame, SFS & concrete

Once applied, Passive Purple X forms a continuous airtight and vapour control layer behind rainscreen systems, brick slips, or insulated render - without requiring any internal disruption.

Typical Use:

  • Retrofit tower blocks

  • High-rise remediation after cladding removal

  • Timber frame or SFS façades

  • Mixed-material substrates

Option 2: Passive Purple + Fred

Enhanced Fire Strategy for Complex Facades




Where fire strategy is the dominant driver, combining Passive Purple with Fred provides a powerful solution.

How the System Works:

  • Passive Purple delivers airtightness and vapour control

  • Fred adds an additional high-performance fire-resistant layer

  • Together, they create a robust, testable, and compliant external envelope

This system is often specified where:

  • Fire engineers require belt-and-braces protection

  • Façade details are complex or irregular

  • Existing substrates vary across elevations

Why Liquid-Applied Systems Win on High-Rise Projects

Sheet membranes struggle on tall buildings due to:

  • Wind exposure

  • Fixing penetrations

  • Poor detailing around balconies and slab edges

Liquid-applied systems like Passive Purple X and Passive Purple + Fred:

✔ Eliminate laps
✔ Seal penetrations automatically
✔ Adapt to movement and irregular geometry
✔ Reduce install time at height
✔ Improve long-term performance

For installers, this means fewer failure points.
For specifiers, it means predictable performance.

Fire, Airtightness & Vapour - Without Compromise

High-rise re-cladding no longer allows trade-offs between performance areas.

These systems deliver:

  • Airtightness compliance

  • Controlled vapour movement

  • Fire-rated external layers

  • Compatibility with modern façade systems

All while being applied entirely from the outside.

Ideal for:

  • High-rise residential blocks

  • Student accommodation

  • Hotels

  • Hospitals

  • Social housing remediation

  • Occupied building retrofits

Speak to the Experts

Every high-rise project is different; fire strategy, substrate, access, and sequencing all matter.

If you’re planning a re-cladding or remediation scheme and need airtightness and vapour control without internal works, Passive Purple X or Passive Purple + Fred can be tailored to your project.

👉 Get in touch for specification support, drawings, and installer guidance.

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