Passive Purple Brush Home Pack 6.9kg - Airtight Paint

£59.99 GBP

excl. VAT

What is Passive Purple Brush?

Passive Purple Brush is a fibre-reinforced, liquid-applied airtight membrane designed for detailed airtightness work. Applied with a simple paintbrush, it creates a permanent, seamless vapour-control layer that seals tricky gaps and penetrations where spraying or rolling is difficult.

Where is it used?

Passive Purple Brush is ideal for:

Service penetrations (pipes, cables, ducts)
Window and door frames
Floor-to-wall and wall-to-ceiling junctions
Cracks and gaps up to 5mm
Touch-ups after air testing or snagging

Why use the Brush version?

Unlike spray-applied Passive Purple, the Brush version contains fibres that span and seal larger cracks and irregularities. This makes it the go-to airtight paint for precision work, detailing, and repairs, while still delivering the same Passivhaus-certified airtightness as the main system.

Surface preparation

Ensure surfaces are solid, dust-free, and closed.
Large gaps (>5mm): Fill with cement-based filler or foam before application.
Small to medium gaps (2–5mm): Passive Purple Brush can be applied directly.

Application & coverage

Applied with a flat paintbrush.
Easy to use for small projects and detailed work.
Once cured, it can be painted, plastered, or rendered over.

Why airtightness matters

Air leakage through cracks and junctions:

Reduces energy efficiency
Allows draughts, damp, and mould
Can compromise Passivhaus and building regulations compliance

By sealing with Passive Purple Brush, you ensure every junction is airtight, securing energy performance and long-term building health.

Tested & Certified

Passive Purple Brush is covered by the same independent testing and ICC-ES evaluation (ESR-4715) as the Passive Purple system:

🌿 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 — air leakage 0.02 L/s·m² at 75 Pa (ASTM E2178)
🔥 Reaction to fire — Class A to ASTM E84 (Flame Spread 0, Smoke 35); Euroclass C-s1,d0 to EN 13501-1 (B-s1,d0 with FRED)
💧 Watertight (EN 14891) & intelligent vapour control (EN ISO 12572)
🧱 Strong adhesion across substrates (EN ISO 4624) & 10/10 mould resistance (ASTM D3273)
✅ ICC-ES ESR-4715, Passivhaus certified & BBA approved

See the full test data & certifications, or read how Passive Purple delivers solar-reflective performance (SRI 52).

🇺🇸 US projects: tested to ASTM standards for world markets — download the US specifications (CSI MasterFormat) or order through WickRight, our Chicago distribution & installation partner.

Related Guides

Helpful guides related to this product:

Quality assurance: Download the free Installation & QA Record sign-off sheet (IM-QA-02) for this product.

Details
Uses
Technical Data
Data Sheets
FAQ

Passive Purple Brush – Airtight Detailing Made Simple

Passive Purple Brush is a fiber-reinforced liquid airtight membrane designed for the details that make or break airtightness. Where tapes, foils, or sprays struggle, Passive Purple Brush delivers a seamless, flexible, Passivhaus-certified seal that protects your building’s energy performance for life.

Why choose Passive Purple Brush?

Passivhaus certified airtight paint for guaranteed performance
Fibre-reinforced formula bridges cracks and gaps up to 5mm
Precision solution for windows, doors, service penetrations, and junctions
Ideal for retrofits and new builds – works across masonry, timber, plasterboard, OSB, and concrete
Water-based, low VOC, safe indoors
Permanent airtight layer – can be plastered, painted, or rendered over once cured

Built for airtightness

Tiny cracks and junction leaks are one of the biggest causes of heat loss, damp, and mould. Passive Purple Brush eliminates these weak spots, ensuring airtight continuity across the building envelope. Whether in a Passivhaus project or a retrofit upgrade, it gives you the confidence of an airtight seal without the hassle of tapes or grommets.

Contact our team at info@intelligentmembranes.com to find out how Passive Purple Brush can transform your airtightness strategy and help you meet UK airtightness standards and Passivhaus requirements.

Passive Purple Brush Uses

Airtight flexible coating that has excellent adhesion on different surfaces such as:

Concrete
Brick
Wood
Floor/wall connections
Ceiling connections
Vertical and horizontal joints

Product Collection: Passive Purple
Applied By:Brush
Colour:Purple

Key Points:

Vapour control layer
Passivhaus certified
Airtight easy to use paint brush applied
Great for retrofit and new builds
Smoke Tight
ICC tested and Certified
BBA approved and Certified
1kg will cover 1m2

Passive Purple Brush - Technical Data Sheet (TDS)

Passive Purple Brush - Install Guide

Passive Purple Brush - Safety Data Sheet (SDS)

BBA Certificate - Passive Purple Brush

Reaction To Mould Growth - Passive Purple Brush

SD Card - Passive Purple Brush

M1 Class - Passive Purple Brush

3D Detail Drawings - Booklet Set One

3D Detail Drawings - Booklet Set Two

3D Detail Drawings - Booklet Set Three

All 3D Detail Drawings

At Intelligent Membranes, we help architects, contractors, retrofitters and self-builders achieve airtightness and waterproofing targets with liquid-applied systems. Our flagship airtight system, Passive Purple®, is airtight at all times yet breathable when the building fabric needs to release vapour — we call this intelligent breathability.

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
P10/60Air and vapour control layer

Uniclass 2015

Pr_25_57_65_60Plastics sheets

View on NBS Source Get specification support

Clause wording

AIR AND VAPOUR CONTROL LAYER – DETAILING
Manufacturer: Intelligent Membranes Ltd, Cambridge. Tel 01223 208174. intelligentmembranes.com
Product reference: Passive Purple Brush, brush-applied airtight vapour control membrane for joints, junctions, corners, window and door perimeters and service penetrations.
Certification: BBA certified. Passivhaus Institute certified component.
Band width: 100 mm total (approx. 50 mm either side of the joint); 150 mm on rough masonry and high-movement joints.
Gaps: Up to 3 mm bridged directly; 3–10 mm backed with backer rod or compatible sealant then coated; over 10 mm closed mechanically first.
Field area: Passive Purple spray/roller grade over the detailing.
Installation: In accordance with the manufacturer's current technical data sheet and installation guide.

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

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