Passive House Concept

The Passive House Institute (Passivhaus Institut) is a distinctly German independent research institute that focuses on the development of the Passive House concept.  This concept is the only internationally recognized, performance based standard in the construction industry.  The Passive House Institute performs research into new building materials, products, and performs certifications worldwide.  To become Passive House certified a building must meet several performance standards.

Important Performance Standards: 

Heating Demand

  • Less than or equal to15  kWh/m^2 annually
  • Or less than or equal to 10 W/m^2
Cooling Demand

  • Less than or equal to 15 kWh/m^2 annually
  • Or less than or equal to 10 W/m^2
Primary Energy

  • Less than or equal to 120 kWh/m^2 annually
Airtightness

  • Less than or equal to 0.6 ACH50 (Air Changes per hour pressurized at 50 pascal)

Although there are several more specific standards for what materials and devices may / must be used in homes that hope to be Passive house certified, these performance standards are the most well known.

Construction Principles:

(Passivhaus Institut Website)

A Passive House must have high quality insulation, and this includes doors, windows, and every other surface exposed to the outside.  Since Passive House construction calls for such an airtight home, it is necessary that there is ventilation to to ensure an adequate supply of fresh air.  To accomplish this without losing all the energy used to heat that circulating air, these homes use a device called a heat recovery ventilator (HRV).  The HRV draws fresh air into the home while extracting the heat from the exhaust air and transferring that energy to the fresh air being brought in.

Lastly, the home must be built with careful attention to thermal bridging, which occurs when something with a low insulation value (structural framing, for example) is allowed to bypass wall insulation and transfer the heat energy from the home to the outdoors.  A well-designed Passive House minimizes thermal bridges.

Impact on Performance:

The Passive House Institute website states that employing the Passive House concept will result in 90% energy savings compared to the average home in central Europe, and about 75% energy savings compared to a newly constructed home in Central Europe.

The Passive House concept is not limited to residential construction.  A Passive House hotel was built in the small town of Torbole, Italy.  This hotel meets the rigorous Passive House standards and allows the public to experience a night in a Passive House so they can decide if they would like to invest in either building a new one for themselves or retrofitting their existing home to Passive House standards.

(zephir.ph)

How the Passive House Concept Stacks Up:

In America we are used to LEED (Leadership in Energy and Environmental Design) certification when it comes to energy efficiency and green construction.  The main difference between LEED and Passive House is that LEED is built on a point system where varying levels of points will get you different levels of certification (LEED Gold, Platinum, etc.).  This can be an issue because a building could have average efficiency, but become LEED certified based on other factors like having a sustainable site and an innovative design process.

With Passive House certification there is never an issue with hiding efficiency since the certification process is based on fulfilling all of the requirements rather than simply getting enough points from a wide list of different possible checkpoints.

If you were directed to this article from the “Like It’s Not Even There: Net Zero-Energy ADUs” blog article, then you know some of the complaints that people have with the idea of net zero-energy homes.  Namely, that some net zero-energy homes are averagely efficient, but simply put enough solar PV panels on the roof to make up for that fact.  With a Passive House building it’s easy to use very few solar panels to reach net zero-energy.

2 thoughts on “Passive House Concept”

  1. All this emphasis on air circulation and heat retention is silly – doesn’t anyone ever open a door or window in these houses? Go outside, come back in again once, twice or more a day? There’s your oxygen replenishment for ya! Maybe a lot more thought and discussion should go into sanely built houses taking climate into consideration, and also why people are living in energy-intensive locations? I used to live in upstate NY and people were always wondering ‘why the houses were so cheap?’ It took me until I was in my 40s to realize it was because the cost of heating and cooling them was so extravagant (not to mention the taxes, thank you NY!) It would seem simply for humans to live in less difficult climates and also more enjoyable.

    1. As a native of Buffalo, NY and current resident of Berkeley, CA, I have to agree on your point about living in a better climate. The heating costs of our drafty 100+ year old windows in our Berkeley house are almost nothing. We certainly don’t have AC here either

      However, much of the air circulation is about getting moisture out of your house. Showers, cooking, breathing and general living produces a ton of water vapor and that can lead to problems with milder and mold so you wan to circulate the air.

      Sure, using your bath fan appropriately or opening windows and doors can get the job done, but let’s be honest, habits are hard to change and people who haven’t bothered to do this in the past are unlikely to start doing it.

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