Grand Designs Passivhaus Premium uses Airtight Membrane

With the return of Grand Designs, this week’s episode ‘North Cotswolds 2023’ (Series 24, Episode 6) saw a couple aiming to create the UK’s first Passivhaus Premium. To achieve this certification, the contemporary two-storey self-build must generate four times the energy it uses. Presenter Kevin McCloud described it as ‘like a miniature power station’.

A large part of achieving any Passivhaus certification is through airtightness. Airtightness improves the efficiency of a building’s thermal insulation by blocking any air that could otherwise penetrate through to the insulation layer, which would result in poor performance and higher running costs. Highly ambitious self-builders Duncan and Liz looked to go beyond the normal and create a certified UK first Passivhaus Premium home.

What is Passivhaus Premium?

As Passivhaus standards continue to gain popularity both in the UK and around the world, some forward-thinking home builders are choosing to push their projects past the original Passivhaus standard. In addition to the established ‘Passivhaus Classic’ which meets net zero targets, there are two further standards which include producing renewable energy in the assessment.

Classic

Passivhaus homes are built to be truly comfortable by being highly thermally insulated and incredibly energy efficient. There are strict requirements that they must adhere to, including an airtightness test, which requires that a home must have a maximum of 0.6 air changes per hour. In basic terms, this means measuring the amount of air that escapes through gaps in a building.

Plus

As well as drastically reducing the energy usage in comparison to traditional buildings, a ‘Passivhaus Plus’ home also produces as much energy as it consumes. The energy generated has to come from renewable sources and provide enough energy to operate the building.

Premium

The highest certification home produces more energy than the building requires to operate which can then be sold back to the grid and used to power other homes. This turns them into Passivhaus Powerhouses.

Image Credit: Passivhaus Trust

Achieving Airtightness

One of the main challenges of any Passivhaus project is achieving airtightness. With over 900 square metres of boarding to tape, Duncan felt that he needed a product that not only sped up the process, but was guaranteed to achieve the airtightness levels he required. Rather than having to meticulously tape over the joints between the boards that make up the walls, he chose to use a brush-on product instead. 

The connections and joints in the walls were painted to bridge the larger gaps for a tough yet flexible seal which allows itself to work with building settlement. Passive Purple Brush is a thick and reliable product which doesn’t risk peeling away or becoming unstuck, leaving a house susceptible to air leakage which could cost in energy and stress. 

Then, to finish the job, Duncan simply sprayed over the top of the joints and the rest of the walls with Passive Purple Spray. The spray-on airtight layer prevents leaks, allowing the insulation to really do its job and minimise the heating down to Passivhaus required levels. But the really amazing thing about it, according to Duncan, is that it’s so simple to use that anyone can do it – even Kevin McCloud.

Results You Can Trust

To prove that all their hard work was worth it (and that our products did their job!), the airtightness test by Building Energy Experts showed that Duncan and Liz’s revolutionary eco home measured an impressive average of 0.415 air changes per hour on the first test.

You can watch our TV debut and entire episode on Channel 4 by following the link to ‘North Cotswolds 2023‘. Look out for Kevin McCloud spraying the walls of the now certified Passivhaus Premium home with airtight paint 29 minutes into the episode. 

You can also find Intelligent Membranes and all of the other suppliers who made this Passive House possible by following the link to the Suppliers List. If you’re looking to create airtightness in your home, or even planning a Grand Designs style self-build, get in touch with us to see how we can help you.