Passivhaus 101: The Complete Guide to Ultra Low Energy Homes
Passivhaus homes are a complete rethink of how we build for comfort, performance, and sustainability. But what exactly does Passivhaus mean? And how do you achieve the standard?
This guide answers many questions and clears up the confusion. Whether you're building from scratch or upgrading an existing home, here’s what you need to know.
What is a Passivhaus?
Passivhaus is a building standard that focuses on energy efficiency, comfort, and long-term performance. The name comes from the German origins of the standard and simply mean “passive house.” It’s a set of principles and measures that help you create a home so well insulated, so airtight, and so efficient that it only needs tiny amounts of energy for heating and normally none for cooling.
The idea? Work with your environment, not against it. Think heat from the sun and our daily activities, natural ventilation, minimal heat loss, and constant fresh air—all whilst increasing comfort levels.
What Are the Five Principles of Passivhaus?
Generally, to achieve the Passivhaus standard in the UK we shall need to give attention to the following key points in our building.
- Excellent insulation – Thick, continuous insulation keeps the temperature stable.
- Airtight construction – Stops heat escaping and cold air entering.
- High-performance windows and doors – Triple-glazed and expertly installed to reduce heat loss.
- Thermal bridge-free design – Avoids weak spots where heat escapes.
- Mechanical ventilation with heat recovery (MVHR) – Ensures a constant supply of fresh, warm air.
However, on their own these measures will not ensure that we can meet or are even near the Passivhaus standard. In addition, three other things are critical.
- Accurate thermal modelling of your building. Use of the Passivhaus Planning Package in the design process is essential to ensuring that we know what we are going to achieve. Without it we are ‘flying blind’ and could be well short of the standard.
- Building professionals, from design through to construction, who know how to work to these standards.
- Quality Assurance. Independent Passivhaus certification will ensure that what we have carefully designed gets built as we want.
Get this right, and you’ve built a home that’s warm, healthy, and affordable to run.
Why Does a Passivhaus Need to Be Airtight?
Airtightness is key to performance. Without it, warm air escapes and cold air creeps in—undoing all your insulation efforts. By sealing the envelope of the building, you stop heat from leaking out and completely eliminate drafts. That means better energy efficiency and a more consistent indoor temperature all year round.
What Are Thermal Bridges?
Thermal bridges are sneaky heat-loss spots in your home—places where heat travels through materials that conduct it more easily (like metal or concrete). You’ll often find them at corners, junctions, and window reveals.
In Passivhaus design, these weak points are eliminated or reduced as much as possible. The goal is to keep the temperature consistent across all surfaces, which also prevents issues like mould and condensation.
How Does an MVHR System Work With a Passivhaus?
MVHR stands for Mechanical Ventilation with Heat Recovery. It’s the backbone of fresh air in a Passivhaus.
Here’s how it works:
- It pulls stale, moist air out of bathrooms, kitchens, and utility rooms.
- It brings in fresh, filtered air from outside.
- As it does, it recovers heat from the outgoing air and uses it to warm the incoming air.
The result? Clean, warm air without opening windows and wasting energy.
Can You Heat or Cool a Passivhaus?
Yes—but you rarely need to.
Because of the insulation and airtightness, a Passivhaus retains heat from people, appliances, and even sunlight. You might need a small heating system in winter or a cooling strategy in summer, but energy demand is minimal.
Some homes use a small air source heat pump. Others rely on underfloor heating, radiators, or even just heat from the MVHR system. Cooling can be handled passively with shading, ventilation, and careful design.
Where Did Passivhaus Come From?
The Passivhaus concept was developed in Germany in the early 1990s by physicist Dr. Wolfgang Feist and Bo Adamson of Lund University in Sweden. They set out to design a house that needed almost no heating. The first Passivhaus was built in Darmstadt, Germany, and it’s still performing to this day.
Since then, the standard has gained global traction—including here in the UK.
What Are the Benefits of Building to Passivhaus Standards?
Building to Passivhaus standards pays off in many ways:
- Lower energy bills – Reduced demand for heating and cooling.
- Improved air quality – Constant ventilation removes pollutants and allergens.
- Year-round comfort – No more draughts or cold spots.
- Sustainability – Lower carbon emissions and futureproof design.
- Long-term value – Higher resale value and lower maintenance costs.
Passivhaus Case Studies
We’ve helped bring several Passivhaus homes to life across the UK. Our case studies, like the Golcar Passivhaus, showcase how it all comes together—from airtight thresholds to ground floor foundations.
Look at some of our case studies here:
The Future of Passivhaus Design
As regulations tighten and homeowners look for smarter ways to cut energy use, Passivhaus is becoming less of a niche and more of a benchmark.
We’re beginning to see a wider application of the standard to more challenging projects such as traditional architecture and heritage retrofits.
Passivhaus Products
At 21 Degrees, we supply and install products designed to meet (or exceed) Passivhaus standards. From triple-glazed windows and MVHR systems to insulation, airtight membranes, and more—we only work with proven solutions that perform.
Visit our product pages or speak to our team about what's right for your project.
FAQs
How many Passivhauses are there in the UK?
As of 2025, over 2300 buildings have been certified to Passivhaus standards in the UK, with many more in the pipeline.
Can you open the windows in a Passivhaus?
Yes, absolutely. You’re not locked in! You can open windows whenever you like, but you won’t need to for fresh air—that’s what the MVHR system is for.
What’s the difference between Passivhaus and EnerPHit?
EnerPHit is the Passivhaus standard for retrofits. It recognises the challenges of upgrading existing buildings while still aiming for excellent performance.
What’s the difference between Passivhaus and BREEAM?
BREEAM is a broader sustainability assessment method without the guarantees of performance that Passivhaus offers. Passivhaus is much more focused on energy use and comfort through building performance.
Do you need to heat a Passivhaus?
Only a little. Most homes need just a small heating input during the coldest days. Some don’t need heating at all.
Do You Want to Learn More?
We are proud to be a Patron Member of the Passivhaus Trust, the official Passivhaus organisation in the UK. There is a wealth of free information on the Trust’s Learning Hub.
Whether you’re planning a new build or thinking about a retrofit, we can help you design and deliver a Passivhaus home that performs.
Get in touch to chat with our team and take the first step towards a comfortable, ultra energy-efficient home.
