What is a Passive House?

What is a Passive House?

The Coolest House on the Block

10-13-2021

At eampact, we strive to help people build a sustainable house in the broadest sense, one that helps mitigate climate change for a sustainable world, but also one that adapts to extreme weather events and is resilient.

We looked into the concept (or movement) of the passive house curious if beyond being “green” it is also “resilient”. In this blog post, we share our conclusions.

Hans Jorn Eich created this video that briefly explains the concept of Passive House.

In this blog post we cover:

  • PHI
  • PHIUS
  • What makes a passive house?
  • Spotlight
  • Resilience - comfort, safety, and happiness!
  • Our final thoughts
  • References

There are a couple of organizations that define, specialize, and promote the concept of passive houses. Their contribution to the concept and methods goes anywhere from research and testing, development and design, to setting standards and certifications.

Let’s first take a look at how they define a “passive house”.

 

PHI

The Passive House Institute (PHI) was the pioneer in setting a passive house standard and driving the notion of a passive house. PHI defines a Passive House as:

“A building standard that is truly energy-efficient, comfortable, and affordable at the same time. Passive House is not a brand name, but a tried and true construction concept that can be applied by anyone, anywhere.”

They further explain that: “A Passive House is a building, in which thermal comfort (ISO 7730) can be provided solely by post-heating or post-cooling of the fresh air flow which is required for good indoor air quality (DIN 1946) without using recirculated air in addition.”

Here is a fun fact: according to PHI, the passive house principle has not been “invented” but rather discovered, and that the first fully functioning passive house was actually a polar ship called the “Fram of Fridtjof Nansen” in 1883.    

 

PHIUS

A different organization working in parallel to PHI and which is focused on North America is called PHIUS - Passive House Institute U.S. They also have a definition of a passive building:

“Passive building comprises a set of design principles used to attain a quantifiable and rigorous level of energy efficiency within a specific quantifiable comfort level. "Optimize your gains and losses" based on climate summarizes the approach.”

Both institutes further elaborate on the passive house benefits.

According to PHI, the passive house “has got it all”, and they mention the following attributes of a passive house: comfort, quality, ecology/sustainability, affordability, and proven ROI from measurement results.

According to PHIUS, the passive building provides unmatched comfort, superb indoor air quality, extremely resilient buildings, and the best path to Net Zero and Net Positive.

 

What Makes a Passive House?

A passive house is a design and construction of a house that eliminates the need for an active heating or cooling system. A passive house will maintain the best comfort for its occupants by keeping the house cool on the inside during summertime, and warm during wintertime. In addition, a passive house will provide its occupants with fresh, healthy air.

This is how it is achieved:

Tight insulation - by properly insulating the inside of the building from the outside, heat and cold are not easily transferred, thus protecting the inside of the building from outside temperatures.

Airtight - this can be thought of as insulation, but the emphasis here is to make sure there is no air leakage from the building. If the building is warm, an airtight design will make sure heat does not dissipate from the inside out.

Ventilation - naturally, a fully insulated and airtight building needs some ventilation. But this concept goes beyond having fresh air. Since heat tends to move (energy) from a hot object to a colder one, in the case of an airtight building, the ventilation system will take that heated (and stuffed) air and move it to the outside. While doing so, it will also bring fresh (and cold) air from the outside into the building. The beauty here is that the warm air while traveling outside will heat the cold and fresh air coming in. Literally, a very cool, and proven concept, and you get both fresh air and energy efficiency in one strike. Such a system also helps manage the mold and dampness of a fully insulated building.

Windows - windows play an important role in passive houses. Their location helps with both lighting as well as heating the building from solar energy. Adding to their location, having high-performance windows will also keep the heat inside and the cold out.

Other elements - it is advised to use materials that reduce what’s called “thermal bridging”. Once more, heat travels from one object to another (from hot to cold), and therefore, avoiding materials that encourage heat transfer is recommended.

 

All the mentioned elements can be even constructed off site. Today, there are manufacturers of prefab passive house, which means the complex wall assembly is manufactured indoors at a dedicated facility. This allows the occupant to enjoy both the benefits of a passive house and of a prefabricated structure.

 

Spotlight

Extreme weather events and economic downturns usually have the most impact on the more vulnerable families and individuals in our society. Finch Cambridge, an affordable housing complex in the city of Cambridge, MA, is also a passive building. 

Providing affordable housing which is also energy efficient means lower bills as well as a healthier and protected environment against extreme weather conditions.

In this case, the developer, Homeowner's Rehab, Inc. (HRI), NEI General Contracting, ICON Architecture, and surely many other subcontractors, passive home builders, and good people in the city deserve the credit for leading the way with a truly sustainable endeavor. Finch Cambridge is now the city's largest affordable housing project built in the last 40 years.

Here are further readings which we found heartwarming, inspiring, and educational about this project and its benefits:

 

Resilience - Comfort, Safety, and Happiness!

The Passive House concept/method provides energy savings which are definitely green and good for the environment, but does it also provide resilience?

As mentioned, the PHI definition of a passive house is a building standard that is truly energy-efficient, comfortable, and affordable at the same time.

The PHI does not declare resilience as one of the movements’ goals, thus resilience is a result of the energy efficiency principles. 

One inherent principle in a passive house that relates to resilience is the strict airtightness requirement that ensures moisture through air and moisture movement through the envelope won’t become a problem.

Other aspects of resilience are not incorporated in the standard. It does declare that besides a high level of energy efficiency, passive house buildings and buildings refurbished to the EnerPHit Standard offer an optimum standard of thermal comfort and a high degree of user satisfaction as well as protection against condensation related damage. 

The word satisfaction implies the desire for comfort, and once again, to achieve comfort throughout the lifetime of a building with a changing climate. We believe resilience should be considered in the design.

As for PHIUS, they do mention in their broader definition of a passive building, that “passive buildings offer tremendous long-term benefits in addition to energy efficiency” and they go on to correctly claim that one of these benefits is “a comprehensive systems approach to modeling, design, and construction produces extremely resilient buildings.”

Tapping into one of the most known experts and leaders in the field of resilience, in a published interview with Alex Wilson, the president of the Resilient Design Institute, he stated that the relationship between resilience and the passive house movement is that “a big part of resilience is buildings that will maintain livable conditions if they lose power or heating fuel and part of it is well insulating the building envelope”. He further states that a “passive house provides a very clear, measurable way to ensure that a house will achieve that passive survivability.”

 

Final Thoughts

Passive houses are a great concept that has proven successful implementations. 

One should definitely think of passive houses beyond their green aspect of being energy efficient, and realize the resilience a passive house provides to its occupants.

If you are building a new home in a climate zone that experiences power outages (due to storms, fires, earthquakes), poor outside air quality (wildfires), high humidity/heatwave, a passive house design and implementation will protect you and your family by offering:

  • Comfort - livable and comfortable temperatures, low humidity, quiet.
  • Safety - good air quality, mold-free.

Retrofitting an existing house in such climate zones is also possible but probably will not yield the same, ultimate, results of a properly designed passive house. However, it can definitely improve the comfort and safety of occupants during extreme weather events coupled with power outages.

Key strategies covered in this blog:

  • Tight insulation 
  • Airtight
  • Ventilation 
  • Windows - location and high performance
  • Other elements (thermal bridging) 

 

KEEP COOL. BUILD RESILIENCE. EAMPACT.

 

References:

Passive House Explained in 90 Seconds - YouTube

Passivhaus Institut 

The Passive House – historical review [ ] 

HRI (homeownersrehab.org)

General Contracting in Massachusetts and Florida Areas- Residential, Healthcare, Hospitality, Historic - NEI (neigc.com)

ICON Architecture

The passive house that's aggressively green 

Cambridge's 'Passive House' Is Built With Focus On Affordable Housing, Climate Change 

Criteria for the Passive House, EnerPHit and PHI Low Energy Building Standard 

Resilient Design: An Interview with Alex Wilson 

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