What Are Passive Houses, and How Are They Sustainable?
Most real estate developers construct buildings and homes that are low-cost and aesthetically pleasing.
Instead of investing in sustainability, they incorporate cheap materials and thoughtless designs that don’t provide much insulation or temperature regulation.
Because of this deficiency, tenants and residents need air conditioning and heating to be comfortable during most of the year. The conditioned air is constantly escaping through thin walls, so the heaters or air conditioning units need to be on all the time to actually work. These amenities consume massive amounts of energy and are terrible for the environment.
When air conditioning equipment is manufactured, installed and disposed of, it often leaks hydrofluorocarbons [HFCs]. These greenhouse gasses have 1,000 to 3,000 times the global warming potential of carbon dioxide [CO2], according to the Environmental Investigation Agency.
The U.S. Energy Information Administration estimated that, in 2018, air conditioning consumed about 377 billion kilowatthours [kWh] of energy. This figure accounted for roughly 9% of total U.S. electricity usage during that year. The fossil fuel industry, another sector that contributes heavily to climate change, provided the vast majority of this power.
Air conditioning is expensive, too. Depending on where you live, the annual cost can range from $60 to $525 or more.
Passive House is a construction standard that is attempting to address these problems, and a passive house is any building that is certified to meet this standard. By implementing high-quality materials and designs that help facilitate an ideal temperature, Passive House drastically reduces the demand for air conditioning and heating.
A Brief History of Passive House
In 1988, during a research trip to Lund University in Sweden, German physicist Wolfgang Feist and his academic host, Swedish physicist Bo Adamson, developed the concept of a building that doesn’t need “active heating.” This idea ultimately grew into the Passivhaus standard.
“The original standard was heavily informed by American experiments in sealed buildings during the 70s and 80s as we reacted to the rising cost of petroleum products resulting from the two Arab oil embargoes,” said architect Murray Levi.
As part of his thesis, Feist began working on the first official passive house, a building in the Hesse state of Germany. In 1996 Feist founded the Passivhaus Institut (referred to as the Passive House Institute in English or PHI), an organization that established a certification system and professional network. Since then there have been tens of thousands of passive house projects around the world, although primarily in Europe.
In 2003 Katrin Klingenberg built herself a passive house in Urbana, Illinois. Her home was the first in the U.S. to meet a passive house standard.
This experience inspired Klingenberg to found e-cological Construction Laboratory (shortened to e-colab), a nonprofit affordable housing development firm based in Urbana. After partnering with the city, the firm became a Community Home Development Organization [CHDO]. In 2007, following increased interest in passive house building in North America, e-colab expanded into Passive House Institute U.S., more commonly referred to as PHIUS.
In 2011 PHI revoked PHIUS’ right to certify projects under the PHI name. Feist claimed that PHIUS had breached contracts and threatened the integrity of the passive house standard by certifying buildings without sufficient documentation.
Since this split — caused by ideological and operational differences — PHIUS has engaged in several legal battles with PHI and other passive house organizations such as ECO Smart Building. Both PHI and PHIUS operate in the U.S., but project managers need to choose one party or the other for their certification.
Since the founding of PHIUS, certain U.S. city and state governments have gradually become more supportive of passive house development. In 2014 New York City Mayor Bill DeBlasio launched a green energy initiative with the goal of 80% reduction of carbon emissions by 2050. Government officials began researching passive houses as a means to reach that target, said Wavelength Lighting CEO Michael Hennessy.
Starting in 2018, the New York State Energy Research and Development Authority allocated $11 million for the Multifamily New Construction Program, an initiative where both PHIUS and PHI participated. More recently Rep. Alexandria Ocasio Cortez spoke at the opening of a 67-unit senior housing complex in Queens that met passive house standards.
The City of Vancouver, Canada has also been a leader in the passive house movement. Last year construction companies worked with the city to build The Heights, the largest passive house complex in the country. California and Pennsylvania have invested significantly as well.
In June, 2019 the New York State Assembly passed the Climate Leadership and Community Protection Act that requires the statewide elimination of utility emissions by 2040. Experts have predicted, Hennessy said, that passive housing will be part of the discussion on how to allocate resources.
“The law doesn’t impact people yet, but it will,” he argued.
Levi added that sustainable updates to codes and zoning regulations have also increased demand for passive housing.
How Does Passive House Work?
A successful passive house can reduce heating and air conditioning use by 90%, according to the PHI. The organization stresses five principles:
- Thermal Insulation
- Passive House Windows
- Ventilation Heat Recovery
- Airtightness of the Building
- Absence of Thermal Bridges
PHIUS also promotes five principles, but with different details and in a different order. For example, the PHIUS standard mentions the absence of thermal bridging, but this concept is not a principle.
Here are their principles:
- “Employs continuous insulation throughout its entire envelope without any thermal bridging
- The building envelope is extremely airtight, preventing infiltration of outside air and loss of conditioned air
- Employs high-performance windows (double or triple-paned windows depending on climate and building type) and doors — solar gain is managed to exploit the sun’s energy for heating purposes in the heating season and to minimize overheating during the cooling season
- Uses some form of balanced heat and moisture recovery ventilation
- Uses a minimal space conditioning system”
Here is a breakdown of some of these principles:
For the passive house model to work, the building or home needs to be tightly sealed with quality, sustainable materials and limited ventilation. If architects and construction managers can meet this condition, the next step is installing a sustainable temperature regulation system.
The most natural source of heating in the world is the sun. This fact is why passive house architects include passive solar design, a structure that maximizes the amount of heat derived from the sun during the winter. Passive house design can also capture radiated heat from appliances such as stoves and refrigerators.
For cooling, passive houses rely on the same structure to minimize heat throughout the summer. The angle of the sun shifts to a point where the building is designed to block and disperse solar radiation instead of absorbing it. It’s also essential to eliminate thermal bridges, pathways such as wall studs that allow cool air to escape instead of holding it.
To maintain air quality and circulation, passive houses use air/heat recovery ventilators (often abbreviated as HRVs). These systems, when implemented properly, can reduce the prevalence of unhealthy substances such as pet dander, mold, dust, volatile organic compounds [VOCs] and excess CO2.
Because passive houses are so tightly sealed, Levi recommended that owners and building managers avoid introducing harsh chemicals such as synthetic cleaning products. Instead they should only buy safe, natural cleaning supplies.
Once the shell of the building is complete, a technician conducts an airtightness test by pumping in air and measuring how much leaks over time. If the house passes this diagnostic, it’s ready to be finalized and live or worked in.
Passive House Materials and Features
The PHI website hosts a “component database” that illustrates how various features fit into passive house design. If you have more of a casual interest in passive houses and feel like the official list is a bit too much to digest, check out our short summary of materials and features people tend to incorporate:
- tankless on-demand water heater
- heat recovery ventilator [HRV]
- energy-efficient windows, often double or triple-glazed
- LED lighting such as what Wavelength Lighting offers
- water-conserving plumbing fixtures
- solar hot water system
- solar panels
- paint with no volatile organic chemicals [VOCs]
- reclaimed wood for floors
- wood fiber insulation boards
- vented rain screen
- cellulose or mineral wool for walls
- Trombe walls
- overhangs and trellises
Here are a few companies that sell these materials and features or help with their installation:
- 475 High Performance Building Supply (general supplies)
- Clarum Homes (passive house services)
- Gutex (wood)
- pro clima (insulation materials)
- LAMILUX (roof lighting)
- LUNOS (HRV)
- Retrotec (insulation/air tightness testing)
Passive House Organizations and Certifications
A building doesn’t need to be certified for people to consider it a passive house, but certification organizations do help with quality assurance and safety. These certifications can apply to the entire project or only to certain aspects such as components or the professionals involved.
PHI and PHIUS are arguably the most influential bodies, but there are several other organizations involved in the passive house movement:
- CertifPHIers Cooperative
- International Passive House Association [iPHA]
- New York Passive House
- New York State Energy Research and Development Authority [NYSERDA]
- North American Passive House Network [NAPHN]
- Passive House Academy [PHA]
- Passive House California [PHCA]
- Passive House Western Pennsylvania
- Urban Green
There are also several passive house certifications offered by a few of these organizations:
Passive House Institute [PHI]
- Building Certification
- Certified Passive House Designer
- Certified Passive House Tradesperson
Passive House Institute US
Are Passive Houses Affordable and Accessible?
Because there are so few passive houses compared to traditional buildings, most people don’t have access to them. They simply don’t live in an area where passive houses have been built, and they usually lack the money, time or skill to build one from scratch. It’s much easier to construct a passive house in New York, for example, than in Wyoming.
Experts agree that passive houses can save money in the long-term because they reduce electric bills. Passive house owner and sustainability consultant Joan Raiselis said her electric bill is around $15-17 a month compared to the average $106 in her region. She estimated that her family will save $50-70K during the next 20 years while the house appreciates in value.
There is a debate, however, on whether the upfront costs of passive houses are a significant barrier. Minkuk Kim, a Certified Passive House Designer and Principal Architect at Marin Architects, said it’s a common misconception that passive houses are only for the wealthy. Raiselis had a similar perspective.
“Depending on how you design it and the materials you use, the data suggests that a passive house is about 10% more to build than a traditional wood frame and ‘insulated to code’ construction,” she said.
The bigger the building, the lower this expense is, according to PHIUS. Constructing a multifamliy passive building, for example, costs roughly 3% more than an ENERGY STAR-certified building.
Other professionals believe the upfront cost can be much higher. Matthias Alleckna, an energy analyst at EnergyRates.ca, claimed that these expenses can climb up to 25% more than the construction of a “regular house.” Hennessy quoted a 7-15% average and said, “Truthfully, passive houses can be very expensive, and the concepts haven’t quite trickled down to lower-cost building yet.”
Fortunately all of these experts agreed that passive housing is rapidly becoming more affordable and accessible. As government support spreads, passive houses could soon be available in many states.
What’s It Like Living in a Passive House?
Several passive house residents have described the experience as feeling more connected to nature. The sun keeps them warm. Windows and skylights are angled to account for seasonal shifts. The house may be passive, but residents need to actively adjust windows and shades based on weather changes.
Raiselis said, “Truly, it is the most comfortable house I have ever lived in. For many reasons, it is very different from the older houses I have inhabited, but there is never a draft, unless you want a bit of air movement; the temperature remains constant unless you tell it not to; the air is super clean and filtered and feels that way.”
In 1997 and 1998 artist Pablo Solmon’s home and studio were nominated for the Texas Lone Star Land Stewardship Award for outstanding natural preservation and restoration. The historic house has passive design features such as thick stone walls.
“The way it is located and the placement of windows allows us to only need heat or AC when conditions are extreme,” Solomon said.
Whether the house is historic and refurbished with modern sustainable features, or built recently, living in a passive house is like going back in time.
“Years ago, everyone had a sense of how to manage a house to allow cross breezes to cool it off as the sun moved from east to west, to close and open windows strategically, to design for the best passive effects,” Raiselis explained. “AC has eliminated those thoughts from the way most of us live in a house.”
Passive houses embody the idea that sustainability is often a blend of new technology and old wisdom. We may have heating and air conditioning at our disposal, and these utilities are necessary for intense weather. Nonetheless, it’s always better to rely on smart design and a connection to nature.
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This is the best overview of the passive house concept I have read. I am altering a 1990’s house to see how passive I can make it. Starting with air sealing the crawlspace and doors. Then I will look into a heat recovery fresh air system and more insulation.
Thank you! I worked very hard on this piece. Good luck with your project!