Airtight White: High-Performance -Fire Rated -Airtight & Vapour Control Membrane for Internal Applications - Spray-applied Airtight Liquid Membrane

Passive Purple® Airtight White – Liquid Airtight Vapour Control Membrane

Product Description

Passive Purple® Airtight White is a BBA Certified and Passivhaus Certified liquid-applied airtight vapour control membrane. It is a high-performance, polymer-based coating designed to create a permanent, seamless airtight seal and vapour control layer on the warm side of insulation.

Applied by airless spray, roller or brush, the product dries to form a durable, flexible and impact-resistant polymer membrane with exceptional adhesion to a wide range of construction substrates.

Passive Purple® Airtight White achieves a certified airtightness performance of 0.03 ACH, significantly exceeding the Passivhaus requirement of 0.6 ACH.

Performance and Function

Once cured, Airtight White forms:

• A seamless airtight membrane
• A vapour control layer
• A certified radon barrier
• A certified methane barrier
• A flexible water control membrane

The coating remains elastic and accommodates structural movement, reducing the risk of cracking and air leakage due to building settlement or differential material movement.

Unlike traditional paper membranes, Airtight White eliminates:

• Rips and tears
• Failing or unstuck tapes
• Staple penetrations
• Ongoing repair works
• Excess waste associated with sheet membranes

This liquid-applied system removes the need for paper membranes, tapes and staples, reducing labour time, repair risk and material waste.

When the substrate is pre-treated with IM Primer, Passive Purple® Airtight White may be left exposed as a finished surface where appropriate.

Areas of Application

Passive Purple® Airtight White is designed for use across the entire internal envelope (warm side of insulation), including:

• Floors
• Walls
• Roof structures
• Joist zones
• Window and door reveals
• Wall-to-ceiling connections
• Mixed material junctions (e.g. brick to concrete, steel to concrete)

It can be applied to either face of the external envelope, provided it remains on the warm side of the insulation.

Substrate Preparation

Surfaces must be:

• Clean
• Dust-free
• Structurally sound
• Closed and consolidated

Large gaps (>5mm) should be filled using fast-setting cementitious materials or polyurethane foam.

Small gaps (2–5mm) should be sealed using Airtight White Brush (high-build brush-grade version).

Excess polyurethane foam should be trimmed flush prior to coating application.

Where the membrane is to remain visible, substrates should first be pre-treated with IM Primer to ensure surface consolidation and optimal finish.

Compatible Substrates

Tested and approved for application to:

• Concrete
• Brick
• Timber and OSB
• Multiplex
• Gypsum block
• Ytong block
• PVC
• Aluminium
• Polyurethane foam
• EPDM rubber
• Roofing membranes

Adhesion values exceed substrate strength in many cases.

Technical Characteristics

• Density: 1.2 kg/L
• Resistance to fatigue movement (EOTA TR008): No cracking or delamination

Adhesion (ISO 4624)

• Red brick: 1.5 N/mm² (dry), 1.4 N/mm² (moist)
• Concrete: 1.9 N/mm² (dry), 1.6 N/mm² (moist)
• Ytong block: > substrate strength, 0.8 N/mm² (dry), 0.7 N/mm² (moist)
• Gypsum block: 1.6 N/mm²
• OSB: > substrate strength, 0.6 N/mm²
• Multiplex: > substrate strength, 0.6 N/mm²
• EPDM: > substrate strength, 1.3 N/mm²
• Roofing: > substrate strength, 0.7 N/mm²
• Plaster on Passive Purple®: > substrate strength, 0.4–0.8 N/mm²

Features and Benefits

• Ready to use
• BBA Certified
• Passivhaus Certified
• Certified radon barrier
• Certified methane barrier
• Achieves 0.03 ACH airtightness performance
• VOC-free
• Carcinogen-free
• Ammonia-free
• Formaldehyde-free
• Seamless membrane formation
• Suitable for new build and retrofit
• Can remain exposed when used with IM Primer
• Suitable for domestic and commercial applications