We recently gained planning permission for an exciting project: the creation of a highly sustainable, new-build, single-storey dwelling in a secluded location in Hertfordshire. Our client is extremely keen to take a pioneering approach, using the most sustainable techniques and materials possible. When complete, Long Barn will be a shining example of how carbon emissions can be significantly reduced to create a sustainable new home.

The first step in designing a low-energy home such as this is to optimise the efficiency of the thermal envelope – the physical separation between the internal and external elements of the building. The performance of the thermal envelope is what determines how much heat is lost and therefore how much energy needs to be used to compensate for it.

One way to achieve a high-performance thermal envelope is to design using Passivhaus principles. The technique creates an accurate prediction of building performance to try to get it to an absolute minimum.

There are several key principles and materials that Passivhaus design focuses on, including:

• High-performing, triple-glazed windows – carefully positioned to make the most of the sun’s energy
• Mechanical ventilation with heat recovery – to provide fresh, pollen and dust-free air
• Airtightness – to prevent heat loss as well as draughts and moisture damage
• Insulation – that keeps warmth in during water and heat out during summer
• Thermal bridge-free design – the weak points in the thermal envelope where heat is transferred from the inner to the outer wall.

To create thermal bridge-free design, at Long Barn we are using a hybrid wall with a cavity filled with wood fibre insulation. Not only is that excellent insulation that creates a warm, airtight structure, but it has associated health benefits. While some insulation materials release compounds during the years following installation – a process called ‘off-gassing’ – natural materials do this to a much lesser extent. The result is much better air quality.

Get in touch if you’d like to talk to us about sustainable design. We’ve been implemented some amazing new materials and techniques on our projects.