Grand Designs North Cotswolds 2023 Passivhaus Premium self-build interior featuring Passive Purple liquid-applied airtight membrane on walls to achieve high airtightness and energy-efficient performance.

Grand Designs Passivhaus Premium uses Airtight Membrane

Grand Designs North Cotswolds 2023: Creating the UK’s First Passivhaus Premium

With the return of Grand Designs, the episode ‘North Cotswolds 2023’ (Series 24, Episode 6) followed an ambitious couple determined to build the UK’s first Passivhaus Premium home.

To achieve this prestigious certification, their contemporary two-storey self-build had to generate four times the energy it consumes. Presenter Kevin McCloud described the project as being “like a miniature power station.”

A core requirement of any Passivhaus certification is achieving exceptional airtightness. Airtight construction enhances thermal insulation performance by preventing uncontrolled air leakage through the building envelope. Without airtightness, insulation performance drops, energy efficiency suffers, and running costs rise.

Self-builders Duncan and Liz set out not only to meet the Passivhaus standard, but to exceed it, aiming for the highest level: Passivhaus Premium.

Project article

What Is Passivhaus Premium?

As Passivhaus standards continue to gain momentum in the UK and globally, many forward-thinking builders are pushing beyond the original benchmark.

There are three recognised certification levels:

Passivhaus Classic

The foundation standard focuses on creating homes that are:

  • Highly thermally insulated

  • Extremely energy efficient

  • Built to strict airtightness requirements

A key requirement is achieving no more than 0.6 air changes per hour (ACH) during an airtightness test. This measures how much air escapes through gaps in the building fabric.

Passivhaus Plus

In addition to drastically reducing energy demand, a Passivhaus Plus home must produce as much energy as it consumes. The energy must come from renewable sources and be sufficient to operate the building.

Passivhaus Premium

The highest certification, Passivhaus Premium, requires the building to generate more energy than it uses. The surplus energy can be exported back to the grid, effectively turning the home into a Passivhaus powerhouse.

Achieving Airtightness at Scale

One of the most demanding aspects of any Passivhaus project is delivering consistent, high-performance airtightness, especially on a large build.

With over 900 square metres of boarding to seal, Duncan needed a solution that would:

  • Speed up installation

  • Reduce risk

  • Guarantee airtight performance

Instead of relying solely on traditional airtightness tapes across every board joint, he opted for a liquid-applied airtight membrane system.

Passive Purple: Brush and Spray System

To seal larger connections and junctions, Duncan applied Passive Purple Brush, a thick, robust liquid membrane designed to:

  • Bridge larger gaps and joints

  • Provide a flexible airtight seal

  • Move with natural building settlement

  • Reduce the risk of peeling or detachment

Once the key junctions were treated, the entire surface was completed using Passive Purple Spray, creating a seamless spray-applied airtight layer across the walls.

This continuous membrane:

  • Prevents air leakage

  • Enhances insulation performance

  • Reduces heating demand

  • Supports Passivhaus airtightness targets

According to Duncan, the simplicity of the system meant it was easy to apply, so straightforward that even Kevin McCloud took a turn spraying the walls during filming.

 

For our full Passive Purple system, contact us

 

 

 


 

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