Coldwells Build at the Green Home Festival – Passivhaus Made Simple

We kicked off with an introduction to Passivhaus. The audience learned how the building standard is truly energy-efficient, comfortable and affordable at the same time. It was developed in the 1990s by the German physicist, Wolfgang Feist, who set out to investigate why low-energy homes often fell short of their potential. He applied his findings to create Passivhaus – a physics-based method for building extraordinary, high-performance homes.

Rupert explained that for a home to qualify as a Passivhaus, it must meet several strict performance targets. One key requirement is that its heating demand must be less than 15 kWh/m² per year, or have a peak heating load of less than 10W/m². 

But what does that really mean?

kWh (kilowatt hour) is a unit of energy, the same units you see on your electricity meter. Larger homes need more heating, so the usable floor area (measured in m²) is factored in.

Here’s how it breaks down in a Passivhaus with a 100m² usable floor area and an average utility cost of £0.10 per kWh: 15 kWh/m²/year x 100 m² x £0.10 per kWh = £150

This means the annual cost to keep the Passivhaus at a comfortable 20°C would be just £150.

Peak heating load refers to the heating power needed to maintain 20°C on the coldest day of the year. The Passivhaus standard requires this to be less than 10W/m².

Calculation for a Passivhaus with a 100 m² usable floor area: 10W/m² x 100 m² = 1000 watts

Rupert explained that this is so efficient, you could technically keep your Passivhaus warm with just a hairdryer on the coldest day of the year!

Building a Passivhaus can be a complex process, from hiring specialist, certified professionals to making crucial design and material decisions. Over the past three years, we’ve worked with John Gilbert Architects to create the Coldwells Build Passivhaus range, simplifying the entire process for self-builders who want the world’s best energy-efficient home. We gave the audience a sneak peek of one of our six contemporary designs, which will be manufactured in our Aberdeenshire workshop by our Passivhaus-certified trades professionals.

We also shared how we're collaborating with landowners and green mortgage providers to help self-builders secure land and financing.

We also highlighted our innovative construction system that allows us to build Passivhaus homes in our workshop and assemble them on-site in a matter of days. This off-site approach not only reduces construction time, cost and waste – but also ensures that our homes are built in a controlled environment, to the highest standards.