Finishing paint AIRTIGHT

liquidwater-basedfor the building industry

Product overview
Passive Purple Airtight White is a VOC-free, water-based airtight membrane providing reliable vapour control and protection against radon and methane gases. It can be applied directly onto finished walls (eg. plasterboard) if a vapour control layer has been missed. When used with IM Primer, it can be left on show or painted over, making it suitable for exposed environments such as car parks, museums, stairwells and other internal spaces.

Key features

• VOC-free, water-based airtight membrane
• Forms a tough yet flexible polymer membrane that moves with the building and resists impact damage
• Can be spray-applied (airless) or roller-applied; white finish can be left exposed or painted over when primed
• Suitable for retrofit applications and where an on-show white finish is required

Performance & Certifications
Independently tested to both ASTM (ICC-ES) and EN standards and can be specified worldwide. Notable performance attributes include high airtightness, radon and methane barrier performance, low emissions and fire classification characteristics.

Tested & Certified — worldwide

• French A+ indoor-air rating & Finnish M1 class — very low VOC emissions (EN 16516 / RTS)
• Passive House Institute Class A airtight — 0.02 m³/h·m² @ 50 Pa (EN 12114)
• Air barrier material — 0.02 L/s·m² at 75 Pa (ASTM E2178)
• Reaction to fire — Class A to ASTM E84 (Flame Spread 0); Euroclass C-s1,d0 to EN 13501-1 (B-s1,d0 with FRED)
• Watertight (EN 14891) & intelligent vapour control, Sd ~0.8–40 m (EN ISO 12572)
• High solar reflectance (white finish reflects more solar energy)
• Radon barrier — diffusion coefficient 3.3 × 10⁻¹² m²/s (ISO/TS 11665-13)
• Methane / ground-gas barrier — low permeability (ISO 15105)
• Strong adhesion — steel 2.7, CLT 1.83, gypsum 1.6, brick 1.5 N/mm² (EN ISO 4624)
• Flexible & crack-bridging — ~219–350% elongation (EN 12311-1)
• Mould resistance 10/10 — no defacement (ASTM D3273)
• Environmental Product Declaration (EN 15804)
• ICC-ES ESR-4715, Passivhaus certified & BBA approved

Application & uses
Airtight White is designed for internal retrofit airtightness upgrades and for areas where a white finish should be left exposed. Typical uses: lofts, basements, car parks, museums, stairwells, lift shafts, plant rooms, walls, floors and ceilings, vertical and horizontal areas, and detailing around service penetrations when paired with the appropriate brush-applied detailing product. It is applied by airless spray for high-speed coverage (up to ~300 m² per day per installer) or by roller for smaller projects.

Related guides

• Passive Purple & Airtight White: Tested & Certified (ASTM & EN data)
• The French A+ indoor-air rating explained
• What Is a Vapour Control Layer? | VCL Explained
• My Builder Forgot the Vapour Control Layer? Here’s How to Fix It
• Reuben College, Oxford – Award-Winning Airtight Basement with Airtight White (case study)

Characteristics / technical specifications

• Product collection: Passive Purple
• Applied by: Spray or Roller
• Colour: White
• Size / pack weight: 11.4kg
• Coverage (typical): OSB: 13–14 m² per pack (coverage varies by substrate and application thickness)
• Certification / fire class: BS Fire Class C | EN 13501-1:2018
• Airtightness performance: Passive House Institute Class A; air barrier: 0.02 L/s·m² at 75 Pa (ASTM E2178)
• Radon / methane protection: certified radon barrier and low gas permeability (ISO standards)
• Adhesion (EN ISO 4624): steel 2.7 N/mm², CLT 1.83 N/mm², gypsum 1.6 N/mm², brick 1.5 N/mm²
• Elongation (EN 12311-1): ~219–350%
• Mould resistance: ASTM D3273 — 10/10
• Emissions: French A+ / Finnish M1 — very low VOC; product is VOC-free
• Environmental: EPD available (EN 15804)
• Application rate / productivity: up to ~300 m² per day per operative when spray-applied (site dependent)
• Finish: white, high solar reflectance