What are passive houses and why are they sustainable?

Passive house is a building standard that attempts to solve the energy problems of the house through the application of high quality materials and designs that help facilitate an ideal temperature, passive house significantly reduces the demand for air conditioning and heating.


A brief history of passive houses

In 1988, during a research trip to Lund University, Sweden, German physicist Wolfgang Feist and his academic host, Swedish physicist Bo Adamson, developed the concept of a building that does not need of “active heating”. This idea eventually became the Passivhaus standard.

“The original standard was largely based on American experiences with tight buildings in the 1970s and 1980s, when we reacted to the rising cost of petroleum products following the two Arab oil embargoes,” explains the architect Murray Levi.

What are passive houses and why are they sustainable 1

Feist started work on the first official passive house, a building in the state of Hesse (Germany). In 1996, he founded the Passivhaus Institut (called in English Passive House Institute or PHI), an organization that sets up a certification system and a professional network. Since then, there have been tens of thousands of passive house projects around the world, but mainly in Europe.

In 2003, Katrin Klingenberg built a passive house in Urbana, Illinois. His home was the first in the United States to meet the passive house standard.

In 2018, the New York State Energy Research and Development Authority allocated $11 million to the Multi-Family New Construction program, an initiative in which PHIUS and PHI participated. Most recently, Rep. Alexandria Ocasio Cortez spoke at the grand 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 nation’s largest passive house complex. California and Pennsylvania have also invested heavily.

In June 2019, the New York State Assembly passed the Climate Leadership and Community Protection Act, which mandates the phase-out of utility emissions across the state by 2040. Experts predicted , said Hennessy, that passive housing will be part of the discussion on how to allocate resources.

How do passive houses work?

A successful Passive House can reduce heating and cooling use by 90%, according to PHI. The organization emphasizes five principles:

  • Thermal insulation
  • Double glazing
  • Ventilation Heat recovery
  • building sealing
  • 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 bridges, but this notion is not a principle.

Here are its principles:

  • “It uses continuous insulation over its entire envelope without any thermal bridge
  • Building envelope is extremely airtight, preventing outside air infiltration and loss of conditioned air
  • Uses high performance windows and doors (double or triple glazed windows, depending on climate and building type): solar gain is managed to harness the sun’s energy for heating purposes during the heating season and to minimize overheating during the cooling season
  • Uses a balanced form of heat and humidity recovery ventilation
  • It uses a minimal space conditioning system.
  • Here are some of those principles:

For the passive house model to work, the building or dwelling must be well sealed with quality durable materials and limited ventilation. If architects and building managers can meet this requirement, the next step is to install a sustainable temperature control system.

The most natural source of heat in the world is the sun. This 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 designs can also capture the heat emitted by appliances such as stoves and refrigerators.

For cooling, passive houses rely on the same structure to minimize heat during the summer. The angle of the sun moves to a point where the building is designed to block and scatter solar radiation rather than absorb it. It is also essential to eliminate thermal bridges, pathways such as studs that allow cold air to escape rather than trap it.

To maintain air quality and circulation, passive houses use air/heat recovery ventilators (often abbreviated as HRV). These systems, when applied correctly, can reduce the prevalence of unhealthy substances such as pet dander, mold, dust, volatile organic compounds [COV] and excess CO2.

Because Passive Houses are so tightly sealed, Levi advised building owners and managers to avoid introducing harsh chemicals, such as synthetic cleaners. Instead, they should only buy safe and natural cleaning products.

After the building envelope is completed, a technician performs an airtightness test by pumping in air and measuring the amount that leaks over time. If the house passes this diagnosis, it is ready to be finished and to live or work in.

It all sounds very complex, but there are even tools to help builders from the moment they start designing, as mentioned by specialist consultancy Espacio BIM -espacioBIM.com-, bim2PH is a tool designed by the Institute Passivhaus which allows information to be extracted from a BIM model linked to Passivhaus design parameters to automatically upload it to the Passivhaus calculation tool (PHPP).

There are also specialized courses in the methodology such as the Master International BIM Manager (+VR) as an opportunity to specialize in BIM and its interoperability with the official tool of the Passivhaus Institut, PHPP.

Materials and characteristics of passive houses

On the PHI website we find a “component database” which illustrates how different features fit together in a passive house design. But here’s a quick summary of the materials and features that people often incorporate:

  • On Demand Tankless Water Heater
  • heat recovery ventilator [HRV]
  • energy efficient windows, often double or triple glazed
  • LED lighting such as that offered by Wavelength Lighting
  • plumbing fixtures that conserve water
  • solar hot water system
  • solar panels
  • VOC-free paint
  • reclaimed wood for flooring
  • wood fiber insulation panels
  • ventilated rain screen
  • cellulose or mineral wool for the walls
  • Trombe type walls
  • cantilever and truss

I hope you have a better understanding of what a passive house is and its advantages, many of which can even be integrated into existing houses and thus improve our home and its energy efficiency, as well as our ecological footprint.

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