A Conversation with Michael Southern on Understanding Passivhaus Design for Domestic Clients
We are sharing insights from Michael, Senior Architect & Certified Passivhaus Designer to highlight the key concepts and benefits of Passivhaus design. Our conversation covers everything from comfort and energy efficiency to costs and certification, offering a comprehensive overview of what it’s like for someone to live in a Passivhaus home.
Q: What exactly is Passivhaus design?
A: Passivhaus is an alternative building standard that delivers energy efficient homes built to a very high standard. These homes provide a higher quality environment, offering a range of health and wellbeing benefits. Designed with energy efficiency at their core, Passivhaus homes are easier to keep warm, maintain a consistent temperature, and are well-ventilated, all while costing less to run.
Q: What is it like to live in a Passivhaus home?
A: Living in a Passivhaus home is all about comfort. One of the main goals of the Passivhaus standard is to create spaces that have a far more consistent internal temperature with minimal fluctuation throughout the day. A mechanical ventilation heat recovery system (MVHR) ensures excellent air quality by eliminating condensation and mould while delivering fresh air and removing harmful air pollutants. Passivhaus homes are also designed to prevent overheating offering a comfortable living environment all year round. Ultimately, this leads to significant improvements in both health and wellbeing of occupants.
Q: Do Passivhaus homes require special ventilation systems?
A: Yes. Passivhaus homes require an MVHR system to maintain high indoor air quality. This system extracts stale air, transfers its heat to fresh air coming into the home, and reduces noise to a minimum. While the system provides all the necessary fresh air, homeowners can still open their windows whenever they wish, adding flexibility to the air circulation.
Q: How much does it cost to build a Passivhaus home?
A: Meeting the Passivhaus standard would be expected to typically involve a cost uplift of approximately 9% compared to homes built to baseline building standards. This is due to the need for higher quality materials like triple glazed windows and the MVHR system, as well as additional design and certification costs. However, it’s possible to achieve the standard within existing budgets through cost-effective strategies. Importantly, the initial investment brings long-term financial benefits. You would see a significant reduction in the home’s running costs whilst the capital value would also remain higher should you come to sell in the future.
Q: How much can a homeowner save on energy bills with a Passivhaus home?
A: Passivhaus homes are extremely energy efficient due to their high level of insulation, airtight construction, and passive heat gains from the sun and occupants. According to the Passivehaus Trust, a typical 90 square metre Passive home can save homeowners around 30% on energy bills compared to a standard new-build home designed to current building regulations. This saving is even greater when compared to older refurbished homes. Passivhaus owners also often have access to more favourable ‘green’ energy tariffs, reducing bills further. See an example of a low energy home here: An Office and Two Houses
It’s also worth noting that Passive houses are constructed to a higher standard due to the quality assurance process needed on site to achieve certification combined with higher quality components, such as triple glazed windows, being used. As the home is built to a higher standard you would expect to see a reduction in ongoing maintenance costs.
Q: Can any house be retrofitted to meet Passivhaus standards?
A: Existing homes can be retrofitted using the principles of Passivhaus design to achieve the EnerPhit standard. While full Passivhaus certification may not always be achievable in order properties, EnerPhit sets out realistic targets that deliver many of the same benefits like improved thermal comfort, lower energy bills and reduced heating demand.
Q: How long does it take to build a Passivhaus home?
A: The timeline for building a Passivhaus home is project-dependent. To achieve the standard, the design process must incorporate Passivhaus principles from the start, and a Certified Passivhaus Designer or Consultant will need to model the design using the Passivhaus Planning Package (PHPP). A Passivhaus Building Certifier also plays a key role in overseeing the construction. While these additional steps are necessary, the overall build time is usually comparable to that of a conventional home.
Q: Are there any design limitations or restrictions with Passivhaus homes?
A: Designing to Passivhaus standards does influence early project decisions, such as the orientation of the building, window placement, and overall form. However, these considerations do not significantly limit design possibilities. Clients can still achieve their dream homes with minimal compromise. In fact, where compromises are made, they often lead to improved living conditions, such as enhanced comfort and air quality.
Q: How does Passivhaus design help reduce carbon emissions?
A: Nearly a quarter of the UK’s carbon emissions come from the energy used in homes. Passivhaus homes significantly reduce this by improving the building’s thermal envelope, using high-quality construction techniques, and leveraging passive heating from the sun, heat recovery, and even occupants. As a result, Passivhaus homes have far lower energy demands, making them an excellent choice for reducing carbon emissions.
Q: What is the process for getting a Passivhaus home certified?
A: To get a Passivhaus home certified, both a Certified Passivhaus Designer and a Passivhaus Building Certifier need to be involved. The Certifier works closely with the design team throughout the process, ensuring that the project meets Passivhaus standards at each stage. During construction, they conduct site visits and quality assurance checks, which help guarantee that the final product not only meets the certification requirements but is also of exceptional quality.
