Passive Purple brush applied airtight paint that has fibres in to span and large gaps to make any form of construction airtight
liquid airtight paint that is brush applied to seal wall penetrations like water pipes
Retrofit airtight paint – Passive Purple applied for improved energy efficiency and airtightness in existing buildings
service pipe airtight paint that is brush applied to make an airtight seal
airtight paint for joist ends on timber frame or masonry builds
airtight paint for joints on OSB timber frame
Airtight paint for masonry builds that is brush applied
paint brush applied Airtight liquid vapour control
Passivhaus certified airtight paint
33%Off!
A+ Certified BBA Certified
SKU: IM/00PPS6.9

Passive Purple Brush – Airtight Paint 6.9KG

$218.05

Internal Airtight Vapour Control Paint (6.9kg) – Brush- Home Pack

Product Collection: Passive Purple
Applied By: Brush
Colour: Purple
Sample Available Here

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Rule of Thumb, you will need 1 tin of brush applied Passive Purple for every 5 tins of spray.

Passive Purple Brush is a VOC-free water-based product. It’s completely free of any nasty chemicals or fumes. What’s more, as a water-based product, cleaning your paintbrushes is a smooth, no mess task!

Passive Purple Brush, powered by fibre-reinforced polymer technology, effortlessly bridges gaps up to 5mm. For optimal efficiency, minimize gaps in the structure to save time and material costs. Once all connections, joints, boards, and penetrations are in place, simply apply with a firm brush to seal gaps and joints with ease.

This significantly reduces air leakage, making any final spray coat—if needed—the perfect finishing touch. With its putty-like consistency and filler-style application, Passive Purple Brush ensures fast, seamless coverage on any surface.

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

Also available in white and a range of different colours, view our product specs for the full selection.

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View Our Case Study Passive Purple Retrofit Installation in London – Airtightness for Energy Efficiency

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  • Key Details

    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.

  • Description

    What is Passive Purple Brush?

    Passive Purple Brush is a fibre-reinforced, liquid-applied airtight membrane designed for detail work in airtightness projects. 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 fibers that span and seal larger cracks and irregularities. This makes it the go-to airtight paint for precision work, details, 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 applying.

    • Small to medium gaps (2–5mm): Passive Purple Brush will cover directly.

    Application & coverage

    • Applied with a flat paintbrush.

    • Easy to use for small projects or detailing.

    • 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.

    Additional information

    Choose Option

    75mm x 25m (Single Roll), 75mm x 25m (Box of 5), 100mm x 25m (Single Roll), 100mm x 25m (Box of 4), 150mm x 25m (Single Roll), 150mm x 25m (Box of 2), 200mm x 25m (Single Roll), 200mm x 25m (Box of 2)
  • Uses

    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

     

  • Data Sheets & Certificates
    Technical Data Sheet
    Install Guide
    Safety Data Sheet
    BBA Certificate - Brush
  • Architects Specification
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  • Delivery

    All delivery charges are included in the price of the products and are dependent on the products selected for purchase. This charge is based on delivery to mainland UK, excluding the Scottish Highlands & the Islands where additional shipping charges will apply. For more information read our delivery policy in full.

    Intelligent Membranes do not offer a next day delivery service.

    Intelligent Membranes aim for deliveries to be with the customer within 2 working days. During the festive period deliveries could take longer.

    Orders placed before 12pm will be dispatched the same day, any orders placed after 12pm will be dispatched the following working day

  • Returns

    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 our returns policy in full.

❓ Liquid Airtightness & Passive Purple Brush – FAQs

1. What is liquid airtightness?

Liquid airtightness is a method of sealing a building’s envelope using a paint-on or spray-applied airtight membrane instead of tapes, foils, or grommets. Once applied, it creates a continuous airtight layer that prevents unwanted air leakage, improves energy efficiency, and helps meet airtightness targets such as Passivhaus.

2. How does airtight paint work?

Airtight paints, like Passive Purple, are vapour-control membranes. They allow the building to breathe (vapour-open) while preventing uncontrolled air movement. Applied by brush, roller, or spray, they create a flexible, seamless layer that’s far quicker to install than tapes or sheet membranes.

3. Why choose liquid airtightness instead of tapes?

  • Faster installation – simply brush or spray onto surfaces.

  • Seamless finish – no weak points from overlaps or joints.

  • Flexible – adapts to irregular surfaces, penetrations, and corners.

  • Retrofit friendly – ideal for sealing existing homes without removing walls.

4. What is Passive Purple Brush?

Passive Purple Brush is the fiber-reinforced airtight paint in the Passive Purple range. It’s applied with a brush and specially designed for detail work, such as sealing:

  • Around windows and doors

  • Pipe and cable penetrations

  • Junctions where roller/spray is hard to use

  • Air test patch-ups and snagging

5. Is Passive Purple Brush Passivhaus certified?

Yes ✅ The entire Passive Purple system is Passivhaus certified, meaning it’s independently tested to meet the world’s strictest airtightness standards.

6. Can I use airtight paint for retrofit projects?

Absolutely. Airtight paint is one of the best retrofit airtightness solutions, because it can be applied internally without major construction work. Passive Purple Brush is perfect for sealing tricky gaps and service penetrations in retrofit homes.

7. Can it replace grommets, tapes, and foils?

Yes – Passive Purple Brush often replaces airtight grommets and tapes around services. Because it’s brush-applied and fiber-reinforced, it forms a permanent, flexible seal even on uneven substrates.

8. What surfaces can I apply Passive Purple Brush to?

It adheres to:

  • Masonry (brick, block, concrete)

  • Timber and OSB

  • Plasterboard

  • Metal penetrations

  • Cables, pipes, and ducts

9. How do I apply Passive Purple Brush?

  • Apply directly with a brush to clean, dry surfaces.

  • Spread evenly to cover cracks, gaps, and junctions.

  • Allow to dry before applying additional coats if required.

10. How long does it take to dry?

  • Touch dry: 1–2 hours

  • Fully cured: 12–24 hours (depending on temperature & humidity)

11. Can I plaster or paint over it?

Yes, once fully cured, Passive Purple Brush can be plastered, painted, or rendered over.

12. Is it safe for indoor use?

Yes – Passive Purple Brush is water-based, low-VOC, and non-toxic, making it safe for internal applications.

13. How long does Passive Purple Brush last?

Once applied and cured, it’s a permanent airtight layer designed to last the lifetime of the building.

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