Passivhaus Airtightness Success in Arrington: Intelligent Membranes & White-Haus Timber Frame

The Project in Detail

In the quiet village of Arrington, just outside Cambridge, Intelligent Membranes delivered the full package of liquid-applied airtightness and weatherproofing solutions on a stunning new timber frame home manufactured and erected by White-Haus Bespoke Timber Frame.

From foundation to façade, inside to out, this project showcases the power of modern methods of construction (MMC) combined with the Intelligent Membranes system:

  • Waterproof Blue Liquid DPM – advanced liquid damp proof membrane applied directly to the kicker blocks/damp course, replacing outdated roll systems.

  • Passive Purple Airtight Vapour Control Membrane – ensuring an internal airtight seal for energy efficiency and long-term durability.

  • Passive Purple External – the world’s first fire-rated (Class B), airtight and breathable external weatherproof façade coating.

  • Passive Purple Brush – fibre-reinforced airtight detail coat used on joints, penetrations, and movement areas.

  • Passivhaus Windows – high-performance Passivhaus-certified window range for unrivalled thermal performance and airtight integration.

This complete intelligent building envelope guarantees airtightness, weatherproofing, breathability, and energy efficiency—a perfect match for modern Passivhaus and low-energy homes.

Step-by-Step Application

1. Foundation Waterproofing

The project began at ground level with Waterproof Blue Liquid DPM. Unlike traditional roll-based damp proof membranes, our liquid system ensures every gap, corner, and block is fully sealed. This provides a seamless waterproof base and the ideal bonding layer for airtight membranes to tie into, creating a continuous barrier.

2. External Weatherproofing

Once the timber frame kit (with hand-cut oak truss roof) was erected, the external shell was sprayed with Passive Purple External. This gave the building its airtight, watertight, and vapour-open façade membrane—ready for cladding and mechanical fixings. Thanks to its unique rubber-like finish, Passive Purple External self-seals around fixings, preventing splits and maintaining full airtightness.

3. Internal Airtight Vapour Control

Inside, a 50mm PIR insulation board was added to the timber frame. At this stage, Passive Purple Brush was used on all joints, service penetrations, and screw fixings—reinforcing high-movement areas. Finally, the internal surfaces were sprayed with Passive Purple, creating a continuous airtight vapour control membrane across the entire internal envelope.

4. Windows & Final Detailing

Once the Windows Passivhaus-certified units were installed, the perimeters were sealed with Passive Purple Brush. With its 45% elongation, the fibre-reinforced formulation flexes with building settlement and structural movement, guaranteeing lifetime airtightness without splitting or degrading over time.

Why This Matters

This project demonstrates how MMC and liquid-applied airtightness systems are the perfect partnership. Compared to tapes, rolls, or traditional membranes, liquid-applied solutions:

  • Create seamless airtightness and weatherproofing

  • Self-seal around fixings and penetrations

  • Save significant installation time

  • Guarantee long-term durability and performance

  • Ensure compliance with Passivhaus standards and future building regulations

By combining Intelligent Membranes with  Timber Frame, this home sets the standard for high-performance, sustainable construction.