What is a Passivhaus?
A Passivhaus is a building designed to use very little energy for heating and cooling, while maintaining a consistently comfortable, healthy indoor environment. The name comes from the German word for “passive house,” which reflects the principle that the building itself does the work rather than relying on active heating systems to compensate for heat loss.
Developed in Germany in 1990, the Passivhaus standard has grown into the most rigorous and widely adopted low-energy building standard in the world. There are now well over 50,000 certified Passivhaus buildings globally, and that number continues to grow.
In this post, we cover everything you need to know from what makes a building a Passivhaus, the five key principles, how certification works, U-value requirements and what Passivhaus construction actually looks like in practice.
Scroll to the end to download this article as a handy PDF guide!
What are the key characteristics of a Passivhaus?
A Passivhaus is defined by a set of measurable performance criteria rather than a prescriptive construction method. This means it can be achieved using a wide range of construction systems from timber frame to masonry to concrete provided the design meets the required standards.
The key characteristics of a Passivhaus include:
- Excellent levels of thermal comfort throughout the year
- Very low energy demand for heating and cooling
- A continuous, high-performance insulation envelope
- An airtight building fabric
- Consistent supply of fresh, filtered air via mechanical ventilation
- High-performance triple-glazed windows
- Thermal bridge-free construction
- Low energy running costs
The Five Principles of Passivhaus Design
The Passivhaus standard is built around five core principles. Together, they work as an integrated system with each one supporting the others to achieve a building that is genuinely low energy without sacrificing comfort.
Thermal insulation
A Passivhaus has a continuous, well-insulated thermal envelope that wraps the entire building. This keeps warmth inside during winter and prevents overheating during summer.
The insulation levels required by the Passivhaus standard are significantly higher than standard UK building regulations. Rather than relying on a heating system to compensate for losses through walls, floors and roofs, the aim is to minimise those losses in the first place. The result is a building that stays at a comfortable temperature with very little energy input.
Airtightness
The Passivhaus has a continuous airtight layer that prevents uncontrolled air movement through the building fabric. This is one of the most important and most demanding aspects of Passivhaus design and construction.
In a standard building, draughts and air leakage account for a significant proportion of heat loss. In a Passivhaus, the airtight layer is carefully designed and meticulously installed to reduce this to a minimum. It requires careful detailing at every junction, penetration and opening, and is tested on site using a blower door test to confirm performance.
The Passivhaus air permeability target is 0.6 air changes per hour at 50 Pascals (ACH50), compared to the standard UK new build target of 5–10 m³/h/m².
Mechanical ventilation with heat recovery (MVHR)
Because the building is airtight, a controlled ventilation strategy is essential. In a Passivhaus, this is provided by a mechanical ventilation with heat recovery (MVHR) system.
The MVHR unit continuously extracts stale air from wet rooms and supplies fresh, filtered air to living spaces. Before the extracted air is expelled, its heat is transferred to the incoming fresh air. It typically recovers 75-90% of the heat that would otherwise be lost. This means fresh air arrives in the building at close to room temperature, maintaining both air quality and thermal comfort without significant energy use.
High-performance windows
The windows in a Passivhaus are triple glazed, with insulated frames and warm edge spacer bars. These are not simply high-specification windows in the conventional sense. They are specifically designed to perform as part of the thermal envelope by minimising heat loss while allowing the building to benefit from solar heat gains during winter.
The orientation and sizing of windows in a Passivhaus is carefully considered during the design process. South-facing glazing can contribute meaningfully to passive solar gain, reducing heating demand further. Shading strategies are also important to avoid overheating in summer.
Thermal bridge-free construction
A thermal bridge is a point or area in the building envelope where heat flows more easily than through the surrounding construction typically at junctions, structural elements, fixings, and openings. In a standard building, thermal bridges can account for a significant proportion of overall heat loss, as well as creating cold spots that can lead to condensation and mould.
In a Passivhaus, the design aims to eliminate thermal bridges or reduce them to an absolute minimum. This requires careful detailing at every junction in the building envelope mainly at foundations, window reveals, balconies, and roof-wall junctions. The Passivhaus Planning Package (PHPP) is used to model and assess thermal bridging throughout the design process.
What is the PHPP?
The Passivhaus Planning Package (PHPP) is the energy modelling tool used to design and verify a Passivhaus building. It is a detailed spreadsheet-based programme that is completed by the architect or designer during the design process.
The PHPP models the building’s energy performance based on inputs including climate data, building geometry, insulation levels, window performance, airtightness, thermal bridges, and the ventilation strategy. It is used iteratively throughout design to test different options and confirm that the building will meet the required criteria before construction begins.
For anyone working on a Passivhaus project for the first time, getting to grips with the PHPP is an important part of the process. Many designers work alongside a Passivhaus certifier or consultant during this stage, particularly on early projects.
What is Passivhaus certification?
Passivhaus certification is an independent process that verifies a building, component, or professional has met the required Passivhaus standard.
Certification of a building
Building certification is carried out by the Passivhaus Institute or an accredited certifier. The process covers the full project from design through to completion and is based on the PHPP calculations alongside supporting documentation. This includes drawings, construction details, manufacturer and component information, airtightness test results, and commissioning data for the MVHR system.
Certification gives clients, occupants and the wider industry confidence that the building will perform as designed. It is not mandatory to certify a Passivhaus building as some projects are built to the standard without formal certification, but certification provides independent, third-party verification of performance.
Passivhaus Classic, Plus and Premium
There are three levels of Passivhaus certification for new buildings:
- Passivhaus Classic is the original standard, focused on achieving very low heating and cooling demand with high levels of airtightness and thermal comfort.
- Passivhaus Plus builds on Classic by also requiring the building to generate a certain amount of renewable energy enough to cover primary energy demand.
- Passivhaus Premium goes further still, requiring the building to generate significantly more renewable energy than it consumes over the course of a year
[Image credit: DLAZEN]
PHI Low Energy Building
The PHI Low Energy Building is aimed at projects where the full Passivhaus standard isn’t achievable but a high level of energy performance is still being targeted. It sits below Passivhaus Classic in terms of stringency.
[Image credit: Passive House Institute]
EnerPHit
The EnerPHit standard applies to existing buildings that have been retrofitted to achieve a significantly improved level of thermal comfort, energy efficiency, and airtightness. Because it is rarely possible to achieve the full Passivhaus standard in a retrofit particularly in terms of airtightness EnerPHit uses a separate, adjusted set of criteria that reflect the constraints of working with existing structures. Like Passivhaus, EnerPHit also has three certification levels: EnerPHit Classic, EnerPHit Plus, and EnerPHit Premium, following the same renewable energy generation logic as the Passivhaus tiers.
EnerPHit is an increasingly important standard in the UK, where a large proportion of the existing building stock needs significant improvement to meet future energy targets.
[Image credit: DLAZEN]
Certification of building components
Building components such as windows, doors, MVHR units, and insulation systems can also be certified by the Passivhaus Institute. Certified components have been independently tested and verified to meet the required performance criteria.
Passivhaus U-values
The U-value requirements for a Passivhaus are determined by the PHPP calculations and will vary depending on the building’s form factor and climate. The values below are a general guide to the levels typically required.
Passivhaus indicative U-value targets:
- Floor: 0.08-0.10 W/m²K
- External Wall: 0.13-0.15 W/m²K
- Roof: 0.10-0.12 W/m²K
- Window: 0.80-1.00 W/m²K
- Door: 1.00 W/m²K
Source: Easi Guide to Passivhaus Design
UK Building Regulations (new dwelling):
- Floor: 0.13 W/m²K
- External wall: 0.18 W/m²K
- Roof: 0.11 W/m²K
- Window: 1.20 W/m²K
- Door: 1.00 W/m²K
Source: Conservation of fuel and power: Approved Document L – GOV.UK
The difference between Passivhaus and standard building regulations is significant. Achieving these levels of insulation performance requires careful consideration of construction type, insulation thickness, and the way junctions are detailed which is where Passivhaus construction detailing becomes very important.
The new Future Homes Standard coming into force on March 24, 2027, will bridge this gap by enforcing improved U-value targets as standard, evaluated via SAP 10.3 and the Home Energy Model (HEM).
Passivhaus construction details
The Passivhaus standard can be achieved using a wide range of construction methods like timber frame, masonry cavity, structural insulated panels (SIPs), concrete, and others. The choice of construction system will shape the approach to detailing, and each system brings its own advantages, constraints, and detailing requirements.
What all Passivhaus details have in common is the need to maintain continuity of insulation, airtightness, and thermal bridge-free junctions throughout the envelope. Small gaps or inconsistencies in any one of these layers can compromise the overall performance of the building.
Understanding Passivhaus: A Simple Guide to Passivhaus Design and Detailing
Passivhaus has always been a standard I find genuinely exciting. The idea that a building can be designed to be this comfortable, this efficient, and this thoughtfully detailed is the kind of work that makes you realise what architecture can really achieve.
But I also know that for a lot of students and early-career architects, Passivhaus can feel like something slightly out of reach. The principles make sense in theory, but translating them into actual construction details, understanding how the insulation continues, how the airtightness layer is maintained, and how each junction is resolved can feel like a big step.
That is why I wrote Understanding Passivhaus. I wanted to create something that made the detailing side of Passivhaus feel more approachable, and that gave people a clear starting point for understanding how these buildings actually go together on the drawing board.
The book covers five different construction types, with over 60 2D and 3D construction details showing how each approach to Passivhaus design is resolved in practice. Whether you are a student encountering Passivhaus for the first time or a professional working toward your first low-energy project, this book is designed to help you build real confidence not just an awareness of the principles, but a practical understanding of what they mean for your drawings.
Because the more architects and designers who feel confident working to this standard, the better the buildings we will all produce.
Passivhaus under construction
One of our readers, Tim Maisey, very kindly shared the images below of a Passivhaus under construction. They give a great sense of what the build process actually looks like with the careful layering and continuity of materials that Passivhaus construction requires.
Frequently Asked Questions (FAQs)
What does Passivhaus mean?
Passivhaus is a German term meaning “passive house.” It refers to a building standard in which the structure itself through high levels of insulation, airtightness, and carefully managed solar gains does most of the work of maintaining a comfortable indoor temperature, with very little reliance on active heating or cooling systems.
What is the difference between a Passivhaus and a standard new build?
The main differences are in performance levels and design rigour. A Passivhaus typically has far higher insulation values, significantly better airtightness, triple-glazed windows, and a controlled ventilation strategy. It is designed and verified using the PHPP to confirm it will meet strict energy and comfort criteria. A standard new build is designed to meet minimum Building Regulations requirements, which are considerably less demanding.
What is the PHPP?
The Passivhaus Planning Package (PHPP) is the energy modelling and design verification tool used in Passivhaus projects. It is a detailed spreadsheet programme that models the building’s energy performance based on its geometry, fabric, climate, and systems. It is used throughout the design process to test strategies and confirm that the Passivhaus criteria will be met.
Is Passivhaus worth it?
For most people considering it seriously, the answer is yes, although it does depend on priorities and budget. The upfront cost of building to Passivhaus standard is typically higher than standard construction, but running costs are significantly lower. More importantly, the quality of the indoor environment in terms of thermal comfort, air quality, and the absence of cold spots or draughts is noticeably better. Many people who live or work in Passivhaus buildings describe the experience as genuinely different to standard buildings.
Can you retrofit a building to Passivhaus standard?
Yes, but it is challenging. The EnerPHit standard was developed specifically for this purpose and uses adjusted criteria that reflect the practical constraints of working with existing structures. Achieving full airtightness in a retrofit is especially difficult, but significant improvements in comfort and energy performance are still possible through a carefully designed EnerPHit approach.
What is the difference between Passivhaus Classic, Plus and Premium?
All three are certified levels of the Passivhaus standard. Classic focuses on achieving very low energy demand for heating and cooling. Plus adds a requirement to generate a certain amount of renewable energy on site. Premium requires the building to generate significantly more energy than it uses over the course of a year. Most certified Passivhaus buildings in the UK currently achieve Classic level.
What construction methods can be used for a Passivhaus?
Almost any construction method can be used to achieve the Passivhaus standard, including timber frame, masonry cavity, structural insulated panels (SIPs), insulating concrete formwork (ICF), and others. The key is not the construction system itself, but how well the insulation, airtightness, and thermal bridge-free detailing are maintained throughout the envelope.
Want to go further with Passivhaus detailing?
If you would like to go deeper on Passivhaus construction details, Understanding Passivhaus covers five construction types with over 60 2D and 3D details designed to help students and professionals understand how the principles are resolved in real drawings. It is a practical reference, not a theoretical overview, and it is one of the most used resources in our construction detailing range.
Find out more about Understanding Passivhaus
You Might Also Be Interested In…
Feel free to check out some of our other Passivhaus content.
Conclusion
I hope you found this article useful and a good introduction to Passivhaus construction.
If you have any questions, please comment below.
Thank you for reading!
Author
Written by Emma Walshaw, Architectural Technologist and founder of First In Architecture and Detail Library. Emma has written a number of books about construction and architectural detailing.
Excellent research and wonderful presentation.Even student can understand it clearly . Well done
Thank you Rohan :)