• A can of White Airtight paint
  • Passivhaus-certified Airtight White applied in heritage building basement.
  • passivhaus airtight air barrier
  • Passivhaus-certified Airtight White applied in heritage building basement.
  • Airtight White liquid airtight vapour control membrane – Passivhaus certified
  • Roof structure at a college retrofit project using Airtight White
  • Airtight White vapour control airtight paint 11.4kg spray and roller applied
  • Airtight White vapour control airtight paint 11.4kg spray and roller applied
  • Airtight White vapour control airtight paint 11.4kg spray and roller applied
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Airtight White - Vapour Control, Airtight & Smoke Tight Paint (11.4kg) - Spray / Roller Applied accreditation
Airtight White - Vapour Control, Airtight & Smoke Tight Paint (11.4kg) - Spray / Roller Applied accreditation
Airtight White - Vapour Control, Airtight & Smoke Tight Paint (11.4kg) - Spray / Roller Applied accreditation
Airtight White - Vapour Control, Airtight & Smoke Tight Paint (11.4kg) - Spray / Roller Applied accreditation
Airtight White - Vapour Control, Airtight & Smoke Tight Paint (11.4kg) - Spray / Roller Applied accreditation
Airtight White - Vapour Control, Airtight & Smoke Tight Paint (11.4kg) - Spray / Roller Applied accreditation

Airtight White - Vapour Control, Airtight & Smoke Tight Paint (11.4kg) - Spray / Roller Applied

Airtight White - Vapour Control, Airtight & Smoke Tight Paint (11.4kg) - Spray / Roller Applied

£99.99 GBP
£99.99 GBP
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Passive Purple Airtight White

VOC-Free Airtight, Vapour & Gas Control Membrane

Passive Purple Airtight White is a VOC-free, water-based airtight membrane providing reliable vapour control and protection against radon and methane gases — without any nasty chemicals or fumes.

Ideal for those on-site “oops” moments, it can be applied directly onto 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 perfect for exposed environments such as car parks, museums, and stairwells.

Once dry, it forms a tough yet flexible polymer membrane that moves with the building and resists impact damage — eliminating the rips, tears, staple holes and failed tapes associated with traditional paper membranes.

Less labour. Less waste. More performance.

Check out our case study

Left on show — see it in 360°

A museum project where Airtight White is doing both jobs at once: the airtightness and vapour control layer on the concrete panel walls, and the finished surface that stays on view.

Click and drag to look around. See all our 360° site tours.

Tested & Certified — worldwide

Airtight White is the white-pigmented version of Passive Purple — the same liquid airtight membrane formulation — independently tested to both ASTM (ICC-ES) and EN standards, so it can be specified 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 — the white finish reflects even more solar energy (the purple grade is independently rated SRI 52, ASTM E1980)
  • 🛡️ 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)
  • 🦠 10/10 mould resistance — no defacement (ASTM D3273)
  • ♻️ Environmental Product Declaration (EN 15804)
  • ✅ ICC-ES ESR-4715, Passivhaus certified & BBA approved

See all test data & certifications →

Quality assurance: Download the free Installation & QA Record sign-off sheet (IM-QA-03) for this product.

  • Details
  • Uses
  • Technical Data
  • Data Sheets

Why Choose Passive Purple Airtight White?

Passive Purple Airtight White is a high-performance liquid airtight vapour control membrane, engineered for projects where airtightness, safety, and sustainability matter most. Certified, tested, and trusted across the industry, it delivers the ultimate balance of speed, protection, and reliability.

  • Certified Performance – Fully BBA Certified and Passivhaus Certified, Airtight White meets the toughest standards for airtightness and building integrity.
  • Underground Gases Protection – Airtight White doubles as a radon and methane barrier, safeguarding your building from harmful ground gases and ensuring a healthier indoor environment.
  • Fast Application, Lower Labour Costs – With airless spray application, a single installer can cover up to 300m² per day, dramatically speeding up build times and reducing costs.
  • Safe & Sustainable – Rated M1 Class and completely VOC-free, Airtight White is water-based, free from harmful chemicals, and safe for both users and the environment.
  • Fire Safety Advantage – Unlike paper membranes (Class E), Airtight White achieves a Fire Class C rating, giving your project a higher level of built-in fire protection.
  • Proven Airtightness – With airtightness results of 0.6 ACH and below, Airtight White helps you achieve Passivhaus standards with confidence – whether you’re aiming for certification or simply building to a higher energy efficiency level.

Passive Purple Airtight White is the smart choice for builders, architects, and retrofit specialists who need a certified, safe, and high-performance airtight membrane that goes beyond traditional tapes and foils.

Airtight White – Spray or Roll for a Seamless Finish

Passive Purple Airtight White is a liquid-applied airtight vapour control membrane designed for projects where airtightness must be achieved without compromising appearance. Applied by airless spray or roller, it creates a smooth, white finish that can be left on show — making it ideal for retrofit projects, heritage buildings, and internal spaces where a clean look is required.

Why Airtight White?

  • Retrofit Ready – Perfect for upgrading existing buildings without the need to strip back walls.
  • On-Show Finish – The white coating blends seamlessly into interiors, making it suitable where airtight layers remain visible.
  • Fast Coverage – Up to 300m² per day can be applied by one installer using spray, or easily rolled on smaller projects.
  • Certified Protection – BBA Certified, Passivhaus Certified, and tested as a radon barrier for complete performance peace of mind.
  • Healthy & Safe – M1 Class, VOC-free, water-based, with zero harmful chemicals.
  • Fire Resistance – Achieves Fire Class C, outperforming traditional membranes.

Where It Works Best

Airtight White is designed for:

  • Internal retrofit airtightness upgrades
  • Areas where white needs to be left exposed (lofts, basements, services zones, car parks, lift shafts, stair wells or plant rooms)
  • Floor, wall, and ceilings
  • Vertical and horizontal areas
  • Service penetrations when paired with Airtight White Brush for detailing

Whether sprayed for large-scale speed or rolled for smaller retrofit projects, Airtight White delivers a seamless, durable, and attractive airtight layer that protects energy performance while looking good enough to leave uncovered.

Product Collection:Passive Purple
Applied By:Spray or Roller
Colour:White
Size:11.4kg
Certification:BS Fire Class C|EN 13501-1:2018, cl. 11

Coverage
OSB: 13 – 14 Sqm

KEY POINTS:

  • Passivhaus certified
  • BBA certified
  • M1 class, voc free (volatile organic compound)
  • Fire class c
  • Up to 300m2 a day per operative
  • 0.03ach (air changes per hour)
  • Adheres to any substrate
  • Radon & Methane barrier

Airtight White - Technical Data Sheet (TDS)

Airtight White - Install Guide

Airtight White - Safety Data Sheet (SDS)

BBA Certificate - Airtight White

Passivhaus Institute Certificate - Airtight White

Radon Certificate - Airtight white

Methane Certificate - Airtight White

Resistance To Mould Growth - Airtight White

Reaction To Fire - Airtight White

Reaction To Fire - Airtight White + FRED

SD Card - Airtight White

EPD Certificate - Airtight White

M1 Class- Airtight White

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.

View full details

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

  • P10/310Air and vapour control layer
  • H92/780Air and vapour control layer

Uniclass 2015

  • Pr_25_57_65_60Plastics sheets
View on NBS SourceGet specification support

Clause wording

AIR AND VAPOUR CONTROL LAYER – EXPOSED WHITE FINISH
Manufacturer: Intelligent Membranes Ltd, Cambridge. Tel 01223 208174. intelligentmembranes.com
Product reference: Airtight White liquid-applied airtight vapour control membrane, spray/roller grade, with Airtight White Brush for joints, junctions and penetrations.
Certification: BBA certified. Passivhaus certified.
Use: Internal airtight and vapour control layer; may be left exposed as the white finished surface.
Detailing: Airtight White Brush applied first to joints, junctions, frames and service penetrations.
Installation: In accordance with the manufacturer's current technical data sheet and installation guide.
Testing: Verify airtightness by pressure test on completion.

Check against the current technical data sheet before issue. Certificates are in the Downloads tab.

Discover which Intelligent Membranes product best fits your build with our handy comparison table.

Watch Airtight White - Vapour Control, Airtight & Smoke Tight Paint (11.4kg) - Spray / Roller Applied in Action