Passive House design is the ultimate solution for energy-efficient building as it requires none to very little active heating. But how does a Passive House work, and what components are needed to build it?
What is a Passive House?
The Passive House concept originates in Germany and is the leading approach for high-quality, healthy and sustainable building. The energy-saving capabilities of a Passive House exceed common building standards by far - not only here in New Zealand but worldwide.
To be called a Passive House, a residential or commercial building must generate most of its heat passively, without active heating. Instead, it uses natural energy sources, predominantly the sun and the heat that human occupants and household appliances create.
The goal is to create an ultra-low energy building that provides a high comfort level and healthy living environment while using very little heating and cooling energy.
A certified Passive House has exceptionally high building standards. The house uses a combination of high-quality building components and techniques, such as high insulation, an airtight building envelope, ventilation with heat recovery, thermal bridge-free construction and high-performance windows to create a controlled internal environment.
This construction method helps generate stable internal temperatures of cosy 19-22°C all year round, day and night, while the outside temperature varies and can drop well below 5°C in winter.
The key - Excellent insulation
Maximum thermal insulation is the key factor for an efficient Passive House. Therefore, Passive Houses are packed in very thickly.
The insulation protects the house against the weather's effects and reduces the risk of overheating on hot summer days, while the inside stays dry and warm all year round. Simultaneously, the rooms are protected against moisture damage from condensation or mould due to constant and controlled air movement.
The importance of high-quality glazing
Typically, windows are the weakest part of a house because they can generate high heat loss rates. It is crucial for a well-functioning, energy-efficient building that the windows and doors are equipped with equally high insulation as the exterior walls.
This is why Passive Houses are built with high-performance double- or triple-glazed windows and energy-efficient doors that help to keep the precious heat inside and moisture outside by avoiding any air gaps.
ECOWINDOWS high-quality, double-glazed windows have two thermally insulated window panes with Low-E (low-emissivity) glass and a hermetically sealed space between them. This space reduces the heat loss significantly because it is filled with Argon, rather than air, a noble gas with low heat-conducting properties. Our triple-glazed windows are made of three glass layers, each covered with a Low-E coating and an Argon filling in between them, reducing heat loss even further.
Using the power of the sun
Overall, the construction has to be thoroughly planned to allow optimal usage of solar power. The trick is to allow plenty of sunshine to enter the house when desired (winter) and easily keep it out when needed (summer).
Therefore, installing as many north-facing windows as possible to catch a maximum of sun rays in the colder months is recommended. Further, the building requires a reliable shading system made of blinds or other fixed shading structures, such as roof overhangs, or similar, to protect against overheating on hot summer days.
Eliminating thermal bridges
A Passive House must be free of thermal bridges, also widely known as cold bridges. These bridges are locally limited areas in the thermal envelope where heat exchange occurs. They exist because heat is always looking for an escape and takes the path of least resistance. In addition to heat loss, thermal bridges can also generate condensation and mould.
Thermal bridges often occur where components meet and materials form a solid connection from exterior to interior surfaces. This is why it is essential to carefully plan all corners, edges and junctions before building the house.
Airtightness - Creating controlled conditions
It is crucial to regulate and control the airflow in the house. To do so, the building envelope of a Passive House must be airtight. Being airtight does not mean that the building must be completely sealed and locked without any fresh air: airtightness only works in combination with a controlled ventilation system (read more about ventilation below).
You can create airtightness by applying one continuous and impermeable envelope that seals the whole building. It is crucial to meticulously plan the airtightness of the construction first because only what is thoroughly planned by the designer can later be made airtight by the builder.
The so-called blower door test can measure and prove the airtightness of the building envelope. The test device consists of a covered metal frame, a fan and a pressure gauge. The device is then clamped onto a window or door to test whether more air is escaping through the joints than is permitted. A Passive House must achieve no more than 0.6 ACH (air changes per hour).
Ventilation
Passive Houses do not rely solely on traditional heating systems such as oil, gas or wood. A sophisticated Heat Recovery Ventilation system regulates and controls the house's airflow, provides constant fresh air and retains heat. This method helps to create a healthy internal environment. The air exchange works very slowly and quietly and is therefore not noticeable, yet very effective.
Even though the Passive House system does not require additional ventilation next to the HRV, it is still possible to manually open windows and doors to ventilate the rooms. However, this will allow the external environment to enter the house. As a result, the internal temperature could change, and moisture, noise and pollutants, such as pollen and fine particles, can enter the building.
Conclusion - Healthy and comfortable living
A Passive House's goal is to create the lowest possible energy usage while providing a high comfort level and a healthy living environment.
The additional technical efforts are likely to result in slightly higher initial design and construction costs for a Passive House than those of a regular building. However, considering that energy prices are on a constant rise and that the finished building will create a much healthier living environment, this higher investment will pay off in the long term.
The Passive House building approach is also in line with New Zealand's target to reduce greenhouse gas emissions. This way, Kiwis can make a smooth transition to a low-emissions future of building sustainably to protect our natural resources for future generations.
Visit our showroom
ECOWINDOWS offers a wide variety of European windows, doors, shading solutions, and ventilation systems, all suitable for Passive House building's high standards and requirements.
Our showroom in Hamilton exhibits a comprehensive collection of our broad product range. We offer you the opportunity to discuss your building project's requirements with our friendly staff and, most importantly, to see, feel, and experience the advantages of our sustainable building solutions for yourself.
If you would like to learn more about our components for Passive House building or discuss your building project, please do not hesitate to contact us today. We look forward to hearing from you!
About ECOWINDOWS - Expertise for Passive House components
ECOWINDOWS is a pioneer in the field of Passive Houses. In 2011, we manufactured New Zealand's first certified Passive House windows. And in 2012, the first-ever Passive House in New Zealand was built with our high-performance windows and a controlled ventilation system that helps keep the house dry, warm and comfortable all year round.
As a member of the “Passive House Institute New Zealand” (PHINZ) and the “New Zealand Green Building Council” (NZGBC), ECOWINDOWS contributes to the mission of creating healthy and highly energy-efficient homes for all New Zealanders.
If you would like to learn more about Passive Houses, eHaus, a recognised expert in New Zealand Passive House design and construction, has some great additional resources on its website which answer more questions about Passive House design.
How does a Passive House work?
Passive House design is the ultimate solution for energy-efficient building as it requires none to very little active heating. But how does a Passive House work, and what components are needed to build it?
