The Growth of Passive House Construction

Pick up a copy of Architectural Digest, Fine Homebuilding, or Dwell and you’re likely to spot some of today’s homebuilding buzzwords like ‘net zero,’ ‘biophilic,’ ‘smart home,’ and ‘minimalist design.’ Among them, you might find mention of something called ‘passive house construction,’ a set of building standards that has been gaining momentum in the new construction industry and reshaping how we think about our built environment. It has even found its way into building codes in the U.S. But what is a passive house?

In the face of escalating energy costs and growing environmental concerns, the construction industry is witnessing a significant shift towards more sustainable building practices. Among these, passive house design concentrates on home energy efficiency and environmental stewardship. This blog explores what a passive house entails, the standards it must meet, its myriad benefits, and how this innovative design principle is shaping the future of construction.

What is a Passive House?

Developed in Germany in the 1990s, Passivhaus, or Passive House Design, is a set of building design standards that achieve high energy efficiency, superior living comfort, and long-term affordability. They can be applied to any building, commercial or residential, anywhere in the world. These low-energy buildings are designed to be air-tight and well-insulated to reduce the need for, and therefore the cost of, active heating and cooling.

How do Buildings Receive Passive House Certification?

Passive houses come in all shapes, sizes, and styles. There is no single, right method for passive house construction, and architects must adapt their designs depending on the climate their structure will be built in. To achieve passive house certification these buildings must follow the 5 core passive house principles:

1. No Thermal Bridging: Thermal bridges, also known as cold bridges, are weak points in a home’s structure such as gaps between the inside and outside of the building. While this seems obvious to avoid, standard home construction can create many thermal bridges such as regularly placed studs that conduct heat through the building’s walls. Through the use of continuous insulation like TimberBoard and carefully chosen construction methods, passive house design eliminates or reduces the impact of thermal bridges.
2. Airtight Construction: Much like thermal bridges, unintended airflow between the inside and outside can increase energy usage. Passive House standards require exceptionally tight building envelopes but do not sacrifice indoor air quality. Passive homes must pass a blower door test with an air-leakage rate of less than 0.6 air changes per hour.
3. Passive House Insulation: High-quality insulation is key to minimizing heat exchange with the outside environment. Passive homes often use 50% more insulation compared to code-built structures and feature energy-efficient, sustainable options like wood fiber insulation that minimize heat loss and ensure buildings are airtight.
4. Energy Efficient Windows: Fenestrations like doors and windows are common weak points in any building. Passive house designs choose energy-efficient windows that employ techniques like triple glazing and low-E coatings to reduce heat conduction. Proper sealing around openings is also important to their efficiency.
5. Ventilation & Heat Recovery: Proper mechanical ventilation ensures fresh air enters the home with minimal heat loss. Heat is transferred from exhausted air to the new air via HRVs or ERVs before circulating through the home.

While these are the central passive house principles, to receive true certification, buildings must meet specific energy standards put forth by the Passive House Institute. Architects and builders are encouraged to contact a certifier early in the design process, allowing problems to be identified and corrected before the build is complete. After construction, they will perform a final inspection of the building and documents. If they meet the criteria, the owner will receive a Passive House Certificate and an optional plaque.

What’s the Difference Between a Passive House and a Net Zero Home?

The concepts of “passive house” and “net zero home” both aim to drastically reduce the environmental impact of residential buildings and improve energy efficiency, but they approach these goals through different means and standards. A passive house focuses on energy conservation and health. The design minimizes the home’s energy requirement for heating and cooling through super-insulation, airtightness, and heat-recovery ventilation systems. The standard doesn’t necessarily mandate the generation of renewable energy but focuses on reducing the need for it in the first place.

A net zero home, on the other hand, is designed to produce as much renewable energy as it consumes over a year, achieving a net zero energy balance. This means the total amount of energy used by the building on an annual basis is roughly equal to the amount of renewable energy it creates.

These two types of energy-efficient home designs may use some of the same techniques to achieve their goals. For example, it’s much easier to compensate for energy use in a net zero home when the building has minimal heat loss thanks to passive house insulation. In fact, dual certification is possible and would significantly reduce the building’s carbon footprint while lowering operational costs.

Can You Retrofit an Existing House to Passive House Standards?

Retrofitting an existing home to meet Passive House standards, while challenging, is indeed possible and is becoming increasingly popular as homeowners seek to reduce their energy consumption and improve comfort. The process begins with a detailed assessment of the current home energy efficiency, using thermal imaging to detect heat leaks, blower door tests to measure airtightness, and energy usage analysis. Then, owners work with a design team to plan the integration of new systems and materials, including upgraded passive house insulation, HVAC, energy efficient windows, etc. After construction is complete the building will undergo the same testing process as new construction to receive its passive house certification.

Passivhaus Case Study: All Wood, All the Time by Opal Architecture

Take this lakeside vacation home in rural Connecticut as an example of modern passive house design. OPAL Architecture set out to build a home that used sustainable, renewable materials to attain its net-zero goals and turned to wood products as the answer. They used cross-laminated timber construction, high performance wood fiber insulation from TimberHP, prefabricated wood panels, and wood finishes throughout the interior and exterior of the home, to name a few. Energy-efficient heat pumps work in tandem with Tesla’ Solar Roof to minimize dependency on the power grid and triple glazed windows make for superior airtightness. Every aspect of the design, construction, and intended use for this building was considered and the result is a gorgeous passive house that is as warm in style as it is in temperature.

The Future of Passive House Construction

As we look towards the future, passive home design is set to play a pivotal role in new construction. It offers a proactive approach to building homes that are not only energy-efficient but also resilient in the face of changing climates and energy landscapes. With the continuous evolution of building materials and techniques, such as those provided by TimberHP, the integration of passive house principles is becoming increasingly feasible and economically attractive.

The rise of passive house is a testament to the construction industry’s capability to adapt and innovate in response to environmental challenges. By embracing passive house standards, the industry does not just contribute to global sustainability goals but also offers substantial economic and health benefits to builders and residents alike. As more stakeholders recognize these advantages, passive house design is poised to become a new standard in the quest for a sustainable future.