What is a Passive House? An Architect's Guide
Passive House is the global standard for sustainable homes. It's a rigorous and exciting development helping create more comfortable and sustainable homes. We've taken a look into what they are, and why we're so passionate about them.
A Passive home is built with comfort and efficiency in mind. The name comes from the German ‘Passivhaus’, a concept developed in the 1990s by Professors Bo Adamson and Wolfgang Feist.“Passive Houses” require no active heating and can be kept warm “passively”, solely by using the existing internal heat sources and the solar energy entering through the windows, as well as by minimal heating of incoming fresh air. Essentially, the design and the choice of materials do most of the work.
What is the goal of a passive house?
The goal of a passive house is simple, according to the international Passive House Institute: “to be highly energy efficient.” Passive houses aim to use 90% less energy than the current housing stock and outperform the energy efficiency of traditional housing. Passive House architects (like our team at Mesh) adhere to key Passive House building principles, and houses are tested against stringent Passive House standards.
The 5 Passive House principles
While the passive house movement originated as a conversation between two professors, ithas evolved into a genuine movement for change, with key principles of sustainable construction and energy efficiency. The five principles of PassiveHouse Design are:
• Thermal insulation: A very high level of insulation is required for passive homes - creating a thick insulation envelope to minimise heat loss through walls and roofs.
• Airtight construction enables ventilation to be tightly controlled, preventing air leakage that can affect temperatures.
• Solar orientation: Passive houses are built with the sun in mind. The most used rooms have windows facing south to make the most of the warmth from sunlight during winter and often include a roof cover to protect against it in the summer.
• Passive house windows: Windows are usually thermally broken, triple-glazed, airtight, and treated to optimise thermal performance
• Balanced heat recovery & ventilation: Passive houses use mechanical ventilation systems to recover heat and circulate air, eliminating the need for energy-intensive air conditioning or ventilation systems.
The Passive House Standard
The PassiveHouse Standard is an international standard for Passive House design established by the Passive House Institute. To be certified as a Passive House, homes must undergo testing, meet specific criteria, and be certified by a registered body. The Passive House certification criteria are:
• Heating demand: Not to exceed15kWh per square metre per year
• Cooling demand: Not to exceed15kWh per square metre per year1
• Energy demand: Not to exceed120kWh per square metre per year2
• Airtightness: A maximum of 0.6air changes per hour at 50 Pascals pressure3
• Thermal comfort: No more than 10%of hours per year over 25°C
1. Allowances made for more humid climates where dehumidification is necessary
2. Classic, Plus, and Premium certificates are awarded based on renewable energy use
3. Verified with onsite testing
What are the benefits of a Passive House?
Passive Houses are a positive force for people and the planet. Designed to live in harmony with their environment, reduce the demand for heat and energy, and create a more comfortable living environment, the primary benefits of a Passive House are:
• Comfort: One of the key drivers behind the passive house movement was to create more comfortable hmes. By regulating temperatures and airflow, homeowners can maintain a comfortable environment year-round, regardless of the outside weather conditions.
• Better air quality: With regulated airflow and a focus on natural materials, there are fewer airborne contaminants, resulting in improved air quality and a healthier lifestyle.
• Reduced energy bills: Passive homeowners can expect heating and cooling-related energy savings of up to 90%, according to the International Passive House Association (IPHA).
• Independence: With less energy requirement, a passive house makes you less reliant on the grid and more independent in the long run. Many passive houses generate their electricity insurplus and can even sell it back to the National Grid.
• Peace & quiet: Equipped with triple-glazed windows and thick walls of insulation, passive houses not only keep your home’s temperature regulated, but they also keep out the sound of traffic, pedestrians, and barking dogs.
Are there any disadvantages to Passive Houses?
While there are many benefits, there are some things to consider as a Passive House owner. Some potential disadvantages include:
• Has to be done from the planning phase: For a house to be a Passive House, you must decide during the planning phase as much of the construction will be guided by Passive House principles. It is, however, possible to retrofit existing homes to less stringent EnerPhit standards.
• Efficient ventilation is essential: As construction is airtight, you must have an efficient ventilation system to maintain air quality. Passive house owners should monitor air quality to ensure CO2 levels don’t exceed recommended levels.
• Backup heating and cooling: Since your house relies on solar heat for passive heating, you may need to use backup heating more frequently if you live in areas with limited sunlight.
• Design restrictions: Due to the requirements for ultra-efficient windows and doors, it’s more challenging to incorporate large windows, as they’re more difficult to insulate. Designs in general may be limited or cost more to customise for your home.
• Higher costs: Passive Houses are often slightly more expensive to build. According to the IPHA, a PassiveHouse in Germany, for example, can cost up to 8% more. However, the long-term benefits and savings of owning one more than pay off the initial cost.
What does a Passive House look like?
While there are very specific guidelines and standards for Passive Houses that limit certain aspects of the build, there is as much diversity of design with Passive Houses as standard housing, if not much more. Here are some examples of passive house projects from around the world:
Lancaster Passive House, JMP Architects
This gorgeous building uses timber panelconstruction and has been clad in a rich Cedar, with timber windows and doors, to reduce its carbon impact. The north-facing roof is covered by a blanket of sedum to increase biodiversity, and the south-facing roof is fully clad in PV panels, which allows "Lancaster Passive House" to generate enough energy to surpass the Passive House Plus requirements
The World’s First Passive House, Wolfgang Feist
Built in Darmstadt, Germany, the world’s first passive house was constructedin 1990 for 4 private clients. These houses are still functioning today and as of 2010, the same four families are still living in them. The measured space heating demand remains 10 kWh/(m²a).
Spring Meadow, Drighlington
One that’s much closer to home is Spring Meadows in Drighlington. Thisdevelopment of 20 new passive homes is built with sustainability at the heart.Designed for families who want to easily commute into Leeds city centre theyshow the versatility of passive homes.
The Deerings, Hertfordshire
A beautifully designed passive home that doesn’t look hugely different to many UK homes. This property also has less than 10% of the materials during construction made from concrete and steel.
Stainbeck Church, Leeds
One of our own Passive projects. This church has been refurbished using passive house principles to reduce excessive heating bills and create a sustainable pillar for the community.
Interested in learning more about Passive Houses or have a project of your own we can help with? Get in touch with our team today.
