Passive House Science


Jon O’Brien, Director of Communications – Master Builders’ Association of Western PA

NOTE: the following article originally ran in BreakingGround Magazine –

Odds are very high that if you are a reader of BreakingGround Magazine that you are familiar with green building certification programs. After all these sustainable programs have been around for decades and heck one could debate that we live in the birthplace of green construction certification with the first LEED pilot projects – The Greater Pittsburgh Food Bank and KSBA Architects – located here.

After a survey of the Master Builders’ Association membership, it was determined that the primary green certifications in the region include: LEED through the U.S. Green Building Council; Green Globes through the Green Building Initiative; and, The Living Building Challenge which is administered by the International Building Institute. As a side note: the MBA’s Green Builders Committee recently hosted a very informative seminar on the three listed certifications, please make sure you’re a recipient of the MBA e-News so that you may be informed of upcoming sustainable construction educational offerings.

While there are numerous green certification programs that are happening in our region, these programs can co-exist due to sustainable champions like the Green Building Alliance, a chapter of the U.S. Green Building Council. The GBA helps to keep the region in the leadership role concerning sustainability and high-performance buildings by focusing on education of green programs that aim to improve the environmental impact of our buildings. This educational effort focuses on the more recognizable certification programs and the lesser known ones too. One in particular that may not yet be widely known but has been increasing its visibility in the region, is Passive House. Passive House is a performance-based building standard which focuses on three criteria: 1. Primary energy demand; 2. Annual heating/cooling demand; 3. Airtightness. Simply put, Passive House is a performance-based building standard that can result in a building to reduce its consumption by as much as 90%.

passive house shady

A Passive House in Shadyside

The origins of the movement are in Germany, where the ideas coalesced into the Passivhaus Institute. The direct translation into English is Passive House but the principles apply equally well to both non-residential and residential buildings. The technical support and certification for Passive House is done by the Passive House Institute of the U.S. (PHIUS), while advocacy and awareness are promoted by Passive House Alliance of the U.S. (PHAUS).

The five principles of Passive House are:

  1. Continuous Insulated Envelope – airtight compact building shape, thermal-bridge-free minimizes transmission losses/gains relative to usable floor area (surface-to-volume ratio) and eliminates condensation in assemblies.
  2. High Performance Windows & Doors – optimal solar orientation, shading and modest windows areas optimize moderate solar gains.
  3. Constant Fresh Air Supply – a balanced mechanical ventilation system with heat and/or moisture recovery applies to most climates.
  4. Managing Internal Loads – efficient appliances, lighting and plumbing minimizes sensible and latent loads and internal heat gains.
  5. Renewables – zero out site, source or carbon through small optimized active PV or wind system.

In practical terms, Passive House is intended to retain as much of the building’s energy and take advantage of as much “free” energy by strategically orienting the building and using the ambient temperature of the exhaust air from the building to act as a heat exchanger or chiller for the fresh air. Once occupied, a Passive House building will use equipment and appliances that use the least energy possible.

To become a Passive House certified building these critical benchmarks must be achieved:

  • Maximum Heating or Cooling Energy: 1.4 kWh/ft2 or 4750 Btu/ft2 (15 kWh/m2) per year
  • Maximum Total Source Energy: 11 kWh/ft2 or 38,100 Btu/ft2 (120 kWh/m2) per year (“Source Energy” by definition includes the energy required to produce and deliver the energy to the site, and can be offset with solar thermal and other measures)
  • Maximum Air Leakage: equivalent to 0.6 air changes per hour at 50 Pascals (ACH50), (~0.03 ACHNAT)

In addition, the following are recommendations which vary based on specific climate change:

  • Window u-value ≤ 0.14 Btu/hr-ft2-°F (0.8 W/m2/K)
  • Ventilation system with heat recovery with ≥ 75% efficiency with low electric consumption @ 0.68 W/cfm/ft3 (0.45 Whm3)
  • Thermal bridge free construction ≤ 0.006 Btu/hr-ft-°F (0.01 W/mK)

Failure to meet the benchmarks means the building is not achieving optimum performance and as a result it will not receive Passive House certification. This certification process uses a whole-building simulation software to measure performance of many variables such as size of structure, number of inhabitants and orientation.

“It is not a difficult process, even though to some it may appear that way,” said Craig Stevenson, Executive Vice President of James Construction and Certified Passive House Consultant. “This certification process demands performance which is different from other historical, prescriptive based sustainability programs.”

Despite being considered by some as the most stringent building energy standard in the world, there are some local commercial projects that have been built, or currently under construction, that abide by the Passive House standard, like: Uptown Lofts on Fifth Avenue, Hilltop Community Healthcare Center, and the renovation of the former McKeesport YMCA into an 84-unit center to house homeless individuals. Two of the three projects listed were built by ACTION Housing, a leading advocate of Passive House in our region.

“Three years ago I had the chance to go to Germany and spend time in Berlin and Freibug to see the abundance of Passive House buildings. When we returned to the U.S. and within a month I had the opportunity to meet Katrin Klingenberg (executive director of the Passive House Institute U.S.). This was really a beneficial educational process for me,” said Linda Metropulos of ACTION Housing. “Shortly thereafter we started working on a house in Heidelberg. Then after this residential project we completed two more Passive House projects – the YMCA renovation in McKeesport and a 14,000 square foot community center in Hazelwood.”


An example of a single-family passive house in Vorarlberg (Austria). Photo: Tõnu Mauring / Flickr

Getting an owner to lead the charge on Passive House was the boost this issue needed. Metropulous explained their attraction to Passive House: “We are all about two things: one, high performance buildings; and two, healthy interiors that feature fresh air for residents. With Passive House, we can focus on what’s important – our projects – and we do not have to be distracted from our projects by worrying about third party verifiers and formulaic methods. The sustainable supporters should be grateful for pioneer organizations like the U.S. Green Building Council and their marketing efforts of LEED; this group was a game-changer and they deserve a lot of credit. However, if we are going to make a significant impact on the existing building stock then we need to focus efforts on building envelopes and energy usage. We are fortunate that the local contracting community can help us work toward our mission as they are willing to learn new tricks and learn from their experiences.”

Mark Whartnaby is partner at Thoughtful Balance Inc., the architects for virtually all of the Passive House projects built in Pittsburgh. He points out that clients interested in Passive House shouldn’t view their project as an “either or” prospect for LEED or Passive House. “If you look at LEED, [certification] is trying to identify all the strategies that can be brought to bear to make the building more sustainable,” Whartnaby notes. “Energy is an important piece but so are the material selections and water conservation, all aspects of the project. Passive House is focused on energy.”

Locally, the Passive House movement is picking up momentum. More construction projects are being built to this standard and the constructors are learning as they go. It is also benefiting the movement by teaming with the Green Building Alliance to create educational opportunities to raise the issue’s awareness in the region. The newly Passive House Western Pennsylvania (PHWPA) is the local chapter of the PHAUS. For more information on PHWPA visit

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