5 Key Steps To Consider When Building a Passive House
Undertaking a Passivhaus build can feel daunting, given the five key principles, EPC (energy performance certification) requirements, legal hurdles, building regulations, and the need for experienced professionals. For first-time builders, hiring experts can make the process smoother and less stressful, allowing you to enjoy the project from start to finish.
Table of Contents
5 Principles To Consider
Step 1: Planning and Design
Step 2: Laying The Foundations
Step 3: Superstructure and Airtightness Test
Step 4: Detailing and Final Touches
Step 5: Final Airtightness Test and Handover
Conclusion: The Future of Living
Contrary to popular belief, passive housing isn’t just about sustainability—it’s about enhancing quality of life by reducing energy consumption, improving air quality, eliminating drafts, and minimising external noise. While building to standard regulations is challenging, passive house standards are even more complex. So, what are the key steps in building a passive house?
The 5 Principles To Consider When Building a Passive House
The Passive House standard is a leading benchmark for energy efficiency in both new builds and retrofits, ensuring homes are efficient and eco-friendly. While some choose official certification through the Passive House Trust for peace of mind, it's not mandatory. Certification can be costly, so many builders opt to follow the principles without pursuing formal accreditation.
Here are the five key principles to consider when building a passive house:
Thermal Insulation
High-quality insulation is essential for all parts of the building—walls, roof, floors, and ceilings. The goal is to drastically reduce heat transfer between the interior and exterior, keeping the home warm in winter and cool in summer. To meet Passive House standards, the U-value (a measure of heat transfer) must be 0.15W/(m²K) or less, ensuring excellent thermal performance.
Ventilation with Heat Recovery
Passive houses rely on mechanical ventilation systems (MVHR - mechanical ventilation heat recovery) that efficiently exchange indoor air with fresh outdoor air. This system maintains optimal temperature and humidity levels, improving comfort while preventing issues like condensation and mould or temperature fluctuations. By recovering heat from outgoing air, these systems help stabilise the indoor environment year-round.
High-Performance Windows & Glazing
Windows play a crucial role in passive house design. Triple-glazed windows with insulated frames are used to minimise heat loss while maximising solar gains. Low-emissivity (Low-E) glass, combined with gases like argon or krypton between panes, helps optimise thermal performance, ensuring homes stay warm without excessive energy use.
Airtightness
One of the key aspects of a passive house is its airtightness. The building envelope must be tightly sealed to prevent unwanted air leaks, which can lead to energy loss and moisture issues. By maintaining a high level of airtightness, passive houses ensure healthy indoor air quality and protect against problems like mould. In fact, a passive house is up to 20 times more airtight than a conventional home, this is what makes them so energy efficient.
Thermal Bridge-Free Design
Thermal bridges are areas where heat can easily escape, typically around windows, doors, and other junctions. To meet passive house standards, every potential thermal bridge must be carefully addressed with proper insulation and sealing. This ensures that heat stays inside, maintaining energy efficiency and comfort.
By adhering to these five principles, a passive house delivers not only excellent energy performance but also superior indoor comfort throughout the year. For those seeking passive house certification, the Passive House Trust offers guidance on meeting these standards, but the principles can be applied without formal accreditation if desired.
The 5 Steps of Building a Passive House
Building a passive house requires a carefully planned process to meet strict energy efficiency standards. Each step, from the initial design to the final airtightness test, plays a crucial role in ensuring the home meets the five passive house principles. This is only a brief outline of the stages of a passive house build, if you would like to understand it in more detail, visit Passive House Trust’s technical guide to building a passive house.
Step 1: Planning & Designing a Passive House
The first step in any passive house project is planning and design. It’s essential to involve a passive house consultant or designer early on, as they will consider design principles that a regular architect might overlook. Skipping this step can be costly and may prevent your home from achieving passive house certification.
Key considerations at this stage include the building envelope, passive house windows, thermal bridge-free design, and energy balance. You'll also need to pass SAP calculations and obtain an EPC before proceeding with the build.
Expert Tip: Start with a PHPP (passive house planning package) calculation. This tool, used by architects and engineers, ensures the build meets energy and housing standards. For more information, check out the PHPP design tools guide from The Passivhaus Trust.
Step 2: Laying Insulated Slab Foundations
Once planning permissions are approved and SAP assessments are passed, it's time to lay the foundations. A passive house foundation includes a well-insulated concrete slab with high-density insulation beneath and around the edges to prevent heat loss. Thermal bridging is eliminated with sealants to ensure airtightness, minimising heat loss through the foundation. This stage also involves site preparation, including ground insulation and moisture protection, to ensure long-term stability and energy efficiency. For more information on laying the foundations of a passive house, take a look at ISOQuick, or Green Raft.
Tip: When selecting insulation for the foundations of your passive house, we would recommend Extruded Polystyrene (or XPS), as it is one of the few insulation materials that is virtually waterproof due to its closed cell structure. It also has very high compressive strength and consistency of structural quality superior to other insulants. This makes it the ideal material for supporting large structural loads in potentially wet conditions.
Step 3: Superstructure (Thermal Envelope) and First Airtightness Test
At this stage, the superstructure or thermal envelope is erected, forming the shell of the build. This includes timber frames, walls, insulation to eliminate thermal bridging, high-performance triple-glazed windows, insulated roofing, and the ‘first fix’ installation of the MVHR (mechanical ventilation with heat recovery) system external wall ducting.
Next, the initial airtightness or "blower door test" is conducted to confirm the structure meets passive house air leakage standards.
Tip: Don’t skip the first airtightness test. It ensures the superstructure is sound and meets passive house standards. Skipping it could lead to delays and issues if an undetected leak prevents EPC certification later.
Step 4: Detailing and Final Touches
After the initial airtightness test, the project moves to the final construction stage, focusing on completing interior and exterior finishes. External contractors handle plumbing, electrical systems, and cosmetic details like plastering, flooring, and painting. This phase also addresses any remaining thermal bridges by applying airtight tapes, spray finishes, and installing external cladding to ensure the structure remains airtight.
Tip: Ensure that any contractors brought in at this stage are aware of the delicacy of the project and the need for attention to detail – any fixings in walls cannot simply be taken out if there is a mistake, they either need to stay there or be carefully taped over (if absolutely necessary) as it could impact the final airtightness of the building.
Tip: If you are intending to go for full Passive House accreditation, take lots of photos – of everything! Better yet, confirm with your PH consultant or designer what photos will be needed in advance and then take more! Closing the performance gap by proving what you have built is the same as what has been designed, is a key principle of the PH construction process.
Step 5: Final Airtightness Test, Optional Certification and Handover
Once the build is completed, a final blower door test ensures the building meets passive house airtightness standards. If successful, the building qualifies for optional certification. While the certification process can be extensive and costly, many choose to do it for peace of mind. Additionally, the ventilation, heating, and renewable energy systems are tested and optimised for efficiency.
The final step is the handover, where contractors educate homeowners on how to operate and maintain these systems, ensuring the home continues to perform efficiently.
Passive Housing With Tŷ Eco: The Future of Living
Investing in a passive house is about more than energy savings—it's about future-proofing your home for upcoming government regulations and environmental goals. With stricter standards aimed at net-zero carbon targets, adopting passive house principles now will keep you ahead. Beyond efficiency, passive house living enhances comfort, sustainability, and overall quality of life. Not only are they more sustainable, but they offer low energy bills, better air quality through controlled moisture levels, a draft-free home with temperatures maintained at 20°-21°, and a peaceful, quiet living space due to superior insulation. It's more than just a home—it's a sanctuary of comfort and health.
Building a passive house is complex, and this is where Tŷ Eco excels. Our expertise ensures every detail, from design to airtightness testing, is handled by certified professionals. Let us guide you through a stress-free, efficient, and rewarding journey to your perfect passive home.
