Passive Purple X (10kg) - Spray/Roller
Passive Purple X (10kg) - Spray/Roller
What is Passive Purple X and How Does it Work?
Passive Purple X is a fire-rated, airtight, watertight and breathable liquid membrane for new-build projects. It is spray or roller-applied to form one seamless coating, replacing the separate layers and laps of a traditional membrane.
Applied internally or externally, it stops air and rain getting through while allowing water vapor to escape, so the building fabric can dry out. It's available in white, cream, black or purple and shares the certified performance of Passive Purple External.
Why Breathable Airtight Paint?
Trapped moisture can damage the building fabric, so a wall needs to keep out air and rain while still being able to dry. Using separate products for fire, water, air and vapor also creates more interfaces where a detail can fail.
Passive Purple X brings those functions together in one continuous layer. With a vapor resistance of Sd ≈ 0.6 m, it lets moisture escape while the coating sheds rain.
It isn't a vapor control layer. Where your design needs one, use Passive Purple.
Spray / Roller or Brush Application
- Spray application: Using an airless machine, one installer can cover up to 300 m² per day.
- Roller application: Ideal if you don't have a spray machine to hand.
- Brush application (Passive Purple X Brush): A 5kg brush-applied version.
Suitability of Passive Purple X
Passive Purple X is designed primarily for new builds, for internal and external use, and can be applied to:
- Concrete, brick and concrete block (CMU)
- OSB and engineered timber panels
- Fiber cement boards and drywall (gypsum board)
- Insulation panels
Working on an existing building? Take a look at Passive Purple Retrofit.
Fire rating: The Euroclass B-s1,d0 classification applies on A1 substrates with a density of at least 653 kg/m³. The designer and building control body should confirm suitability against the building's fire strategy.
The Benefits of Passive Purple X
- ✅ Fire rated: Euroclass B-s1,d0 on qualifying substrates and ASTM E84 Class A
- ✅ Airtight and smoke-tight: One continuous, seamless layer
- ✅ Watertight but breathable: Keeps rain out and lets vapor escape
- ✅ Crack-bridging: Tested at 23°C and -10°C
- ✅ UV-stable: Tensile strength increases after 500 hours of UV exposure
- ✅ Protects concrete: Class C1 CO₂ and carbonation barrier
- ✅ Water-based and low emission: EMICODE EC2 rated
Airtightness and Breathability, Explained
- What is airtightness? Controlling unintended air leakage through the building fabric.
- What does breathable mean? Water vapor can pass through the membrane, while liquid water and air can't.
- What are the airtightness standards? New homes in England must achieve 8 m³/(h·m²) at 50 Pa or better, while Passivhaus requires ≤0.6 ACH.
- Why does it matter? Good airtightness reduces energy loss and improves comfort, while breathability allows the building fabric to dry.
Passive Purple X and Passivhaus
- What is Passivhaus? A building standard focused on extreme energy efficiency and occupant comfort.
- What are the five principles? Airtightness, insulation, high-performance glazing, thermal bridge-free design, and ventilation with heat recovery.
- What is the certification? Passive Purple X shares Passive Purple External's Passive House Institute component certification, Class phB.
Preparation & Application
Great airtightness starts with the right prep:
- Remove salt efflorescence, dust, loose material and standing water. Damp surfaces are fine.
- Make sure the surface is closed, filling holes and joints with a fast-setting cement-based product or polyurethane foam.
- Don't add water or solvents.
- Don't apply below 5°C (air and substrate temperature), in full sunlight or during rain.
- Apply two coats, letting the first dry before applying the second.
- Clean tools with water after use.
How Much Will You Need?
| Substrate | Approx. coverage | Per 10kg tub |
|---|---|---|
| OSB and drywall | 0.8–1.0 kg/m² | 10–12 m² |
| Concrete block and brickwork | 1.0–1.2 kg/m² | 8–10 m² |
Coverage varies with substrate type, porosity and surface condition. Use a wet film gauge to check thickness during application.
Tested & Certified
Passive Purple X shares the certified performance of Passive Purple External, independently verified to European (EN) and US (ASTM) standards:
- Reaction to fire: Euroclass B-s1,d0 (EN 13501-1, on A1 substrates ≥653 kg/m³) and ASTM E84 Class A (Flame Spread 0, Smoke 15)
- Watertight: Class W1 (EN 13859-2), water permeability Class W3 (EN 1062-3) and near-zero water absorption (EN 16302)
- Breathable: Sd ≈ 0.6 m (EN ISO 12572)
- Crack-bridging: A3 at 23°C and A4 at -10°C (EN 1062-7)
- Carbonation barrier: CO₂ Class C1 (EN 1062-6)
- Adhesion: Up to 1.23 N/mm² on CLT (EN ISO 4624)
- Low emission: EMICODE EC2
- Anti-fungus: Rating 0
- Kiwa BDA Agrément: BAW-21-214-P-A-UK, with assessed durability of around 60 years
- Passive House component: Class phB
- US water-resistive barrier: ICC-ES AC212
Related Guides
Quality assurance: Download the free Installation & QA Record sign-off sheet (IM-QA-06) for this product.
Connect the Membrane at Windows and Junctions
Plan the adjoining tape detail as well as the coated area. Our airtightness tape guide covers width and substrate selection, while tape versus liquid membrane explains compatible interfaces, preparation and inspection. Use the specified coating-to-tape detail and check continuity before covering.
Shipping & returns summary
Shipping & returns summary
We, at Intelligent Membranes, would like you to be 100% satisfied with your purchase and our service. In the unfortunate event of any item being unsuitable or wrong, please read the following for advice on returning goods to us.
For architects and specifiers
How to specify this product
The NBS clauses and Uniclass codes this product is specified under, with clause wording you can paste straight into your specification.
NBS clauses
- P10/320Breather membrane
- H92/785Breather membrane
- H22/130Breather membrane
Uniclass 2015
- Pr_25_57_10_94Vapour-permeable sheets
Clause wording
BREATHER MEMBRANE – LIQUID APPLIED Manufacturer: Intelligent Membranes Ltd, Cambridge. Tel +1 (347) 220 8403. intelligentmembranes.com Product reference: Passive Purple External / Passive Purple X liquid-applied airtight, rain-tight, vapor-permeable membrane, spray/roller grade, with Passive Purple External Brush for detailing. Use: Internal and external faces of the building envelope, including façades. Reaction to fire: Class B to EN 13501-1 (Passive Purple X: B-s1,d0 on A1 substrates of density 653 kg/m³ or more). Certification: Passivhaus Institute certified. KIWA approved. Properties: Airtight, rain-tight, vapor-permeable, crack-bridging and UV resistant. Installation: In accordance with the manufacturer's current technical data sheet and installation guide. Note: Designer and building control body to confirm suitability against the fire strategy for the building.
Check against the current technical data sheet before issue. Certificates are in the Downloads tab.
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