Overview – Achieving Outstanding Airtightness in a London Retrofit with Passive Purple

This London retrofit was a full-scale transformation, combining a complete property strip-out with the construction of new, high-performance extensions. The objective was simple but ambitious — to deliver a modern, energy-efficient home that meets and exceeds airtightness standards.

Central to the success of this project was the use of Passive Purple airtight membranes. Applied with precision, these innovative liquid-applied solutions formed a seamless, continuous airtight and vapour control barrier across the entire building envelope. Every junction, gap, and penetration was meticulously sealed to eliminate air leakage, boost thermal efficiency, and ensure long-term performance.

By integrating advanced airtightness technology with expert on-site application, we achieved an exceptional airtightness score. This result reduces heating and cooling demands, lowers energy bills, prevents condensation issues, and significantly enhances occupant comfort.

This project demonstrates how retrofitting with Passive Purple can transform an existing property into a future-ready, high-performance home — delivering sustainability, durability, and full compliance with modern energy efficiency regulations.

Background – Creating a Continuous Airtight Barrier with Passive Purple

This London retrofit project began with a complete strip-out of the existing property, giving us a clean foundation for both airtightness upgrades and energy performance improvements. With the structural works and new extensions underway, our focus shifted to one of the most critical components of a high-performance building — establishing a fully continuous airtight barrier.

We began by applying Passive Purple External Brush to every connection and junction. This meticulous sealing process targeted potential weak points where air leakage is most likely to occur. To reinforce these areas, Airtight Fleece Tape was installed around edges, corners, and other challenging junctions. This specialist tape delivers extra protection against both air leakage and thermal bridging, ensuring no part of the building envelope is left vulnerable.

Next, we applied Passive Purple Internal Vapour Control Layer by spray across prepared blockwork, ceilings, and junctions. This created a seamless, liquid-applied membrane that functions as both an airtightness layer and a vapour control barrier. The result is a robust building envelope that prevents heat loss, controls moisture, and supports long-term energy efficiency.

This multi-stage approach not only improves airtightness but also safeguards the building against condensation and damp, creating a comfortable, healthy, and sustainable living environment for years to come.

Solution – Delivering Exceptional Airtightness with Passive Purple

For this London retrofit project, our airtightness strategy was built on meticulous preparation and the use of premium airtightness products. Every step of the installation was carefully executed to seal all potential air leakage points and maximise thermal efficiency.

We began by applying Passive Purple Brush to all joints, service penetrations, and junctions. This high-performance, liquid-applied airtight coating forms a flexible yet durable seal, closing even the smallest gaps that can compromise airtightness. Once these critical points were addressed, we spray-applied Passive Purple Internal Vapour Control Layer to create a seamless, continuous barrier across all prepared blockwork, ceilings, and connection points. This layer not only ensures exceptional airtightness but also acts as a robust vapour control membrane, preventing unwanted moisture transfer through the building envelope.

To further enhance performance, Airtight Fleece Tape was installed in difficult-to-reach areas, around complex junctions, and along edge details. This specialist tape provided an additional layer of protection, ensuring that no area was left vulnerable. The loft area—a common source of air leakage in many properties—received comprehensive airtight treatment, eliminating one of the most notorious weak spots in building envelopes.

By combining liquid-applied airtight membranes with specialist sealing tapes, we delivered a continuous, high-performance airtight envelope. This approach not only set the stage for exceptional air testing results but also guarantees long-term energy savings, improved occupant comfort, and superior building durability.

AIR TESTING

Air testing—also known as air permeability testing, air leakage testing, or air pressure testing—measures the amount of air escaping through a building’s envelope.

Client Feedback – Real Results from a Passive Purple Retrofit in London

Homeowners across London are increasingly experiencing the transformational benefits of Passive Purple airtightness solutions for retrofit projects. From dramatically reduced energy bills to enhanced comfort and long-term sustainability, the results speak for themselves.

“My house was a vision in purple – inside and out! Watching the Passive Purple application process was genuinely fascinating. The attention to detail was incredible, and it’s given me real peace of mind. I’m no longer dreading my energy bills, and I know my home will be warmer, more energy-efficient, and far more comfortable all year round.”