Passive House design is the ultimate solution for energy-efficient building as it requires none to very little active heating. But how does it work, and what makes a building qualify for the title?

What is a Passive House?

Originating in Germany, Passive House (German: Passivhaus) is a globally recognised standard for high-performance, sustainable buildings. The energy-saving capabilities of these homes exceed common building standards by far as they provide a high comfort level and healthy living environment while using very little heating and cooling energy.

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.

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.

 

Key Components of a Passive House

1. 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.

 

2. High-Performance Windows

Windows are typically the weakest part in a building envelope as 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.

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. 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. ECOWINDOWS offers a range of these windows.

3. Solar Gains & Shading

Overall, the construction must 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.

4. Thermal Bridge-Free Construction

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.

5. Airtightness

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 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).

6. Ventilation with Heat Recovery (HRV)

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. This will allow moisture, noise and pollutants to enter the house and the internal temperature could change.

The Benefits: Comfort, Health & Sustainability

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.

ECOWINDOWS – Passive House Pioneers

In 2011, we manufactured New Zealand’s first certified Passive House windows. A year later, the country’s first-ever Passive House 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), we’re committed to helping Kiwis build healthier, more energy-efficient homes.

Want to learn more? We recommend eHaus for in-depth resources on Passive House design in New Zealand.

Visit Our Showroom

Our showroom in Hamilton exhibits a comprehensive collection of European windows, doors, shading solutions, and ventilation systems, all suitable for Passive House building’s high standards and requirements.

Meet with our friendly team, discuss your building project, and experience the benefits of high-performance building firsthand.