By Ken Levenson, AIA
Passive House is an international building energy standard, and a methodology to meet that standard – developed by the Passive House Institute (PHI) in Darmstadt, Germany. Passive House turns traditional notions of energy efficiency on their head. Instead of being about compromise and sacrifice for only incremental benefit, Passive House demands dramatic energy savings to address climate change head-on, and in so doing, counter intuitively, provides occupants greater comfort and health, a better life and a more resilient existence. Consequently Passive House represents a paradigm shift – challenging our imaginations to make a better world, and daring us to rise and meet the threat of climate change.
A look at Passive House characteristics, its metrics, its methodology and its results can provide an introductory glimpse into how this is possible.
Passive House Characteristics:
- Very Energy Efficient: Providing dramatic energy reduction, up to 90% for heating and cooling demand from average existing building stock – offering a proportional response to the climate crisis confronting us.
- Healthful: Fresh, high-quality indoor air with very low levels of typical contaminants.
- Comfortable: A quiet interior environment with steady temperatures and no drafts.
- Affordable: Added costs of high-performance features are substantially offset by a reduction of systems’ sizes. Occupancy is affordable because the reduced energy use translates into lower bills and protection from future energy price shocks.
- Predictable: An integrated methodology and energy model provides performance predictability, an essential element in optimizing system sizing and costing.
- Resilient: Passive House buildings foster greater resilience in three ways.
- By indefinitely maintaining habitable interior temperatures in freezing weather without power, allowing people to shelter-in-place.
- Power distribution systems can be more robust and flexible with lower demand.
- Reduced power demand makes Net Zero Energy building readily achievable with rooftop photovoltaic solar panels or other onsite renewables.
The Standard: The term Passive House is used because “thermal comfort is achieved to a maximum extent through passive measures (insulation, heat recovery, passive use of solar energy and internal heat sources).” So while the objectives of Passive House are broad, perhaps disconcertingly, the standard focuses on energy usage. The standard doesn’t mandate sustainability measures we’ve come to expect such as green materials, water conservation or transportation sensitivity to name a few – these are the prerogatives of the design-build team. To oversimplify here, we can boil down the standard requirements for new construction to basically three numbers:
- Heat Energy Demand: 4.75 kiloBTUs per square foot of treated floor area per year.
- Primary Energy Demand: 38.0 kiloBTUs per square foot of treated floor area per year. This number is to ensure that all the energy saved in optimizing heating demand is not then wasted in equipment and plug loads.
- Airtightness: 0.6 ACH50. This means, when pressurized or depressurized with blower door fans at 50 Pascals pressure, the building enclosure leaks no more than 60% percent of its interior occupied air volume over the course of an hour. This is extremely airtight. Because air tightness has the single greatest impact on energy efficiency this is the one physically confirmed measurement.
Because of this narrow and clear focus, again counter intuitively perhaps, Passive House has been able to grow rapidly in acceptance around the globe in the past few decades.
A Short History: The first contemporary Passive House was constructed as an experiment in Darmstadt-Kranichstein, Germany in 1990 following an international scientific research project by German physicist Wolfgang Feist, Swedish academic Bo Adamson and others. This effort developed high-performance prototypes for critical building components such as windows, ventilation and thermal-bridge-free connections. The scientific experiment was then developed into a functional energy standard with the formation of the Passive House Institute (PHI) by Wolfgang Feist.
PHI is an independent research institute dedicated to the research “and development of construction concepts, building components, planning tools and quality assurance for especially energy efficient buildings.” To assure quality Passive House buildings PHI has developed a comprehensive and transparent energy model and planning tool, the Passive House Planning Package (PHPP). PHI has also researched and developed protocols for certified building components, the training of professional designers and contractors and the certification of buildings. Through continuous research and data collection from actual buildings and dynamic simulations the energy model algorithms are continually improved upon and make it the first validated truly global standard.
Today there are tens of thousands of Passive Houses around the globe in every imaginable climate and in all major building types: factories, schools, apartment buildings, high-rise office buildings, in both new construction and retrofit. The capital region of Brussels Belgium has fully incorporated Passive House into its energy and building planning so that in 2015 all new construction and substantial retrofits for both private and public buildings will be required to be Passive House.
Part 2, covering Methodology, Components, and Results, will appear in the December issue of Green Energy Times.
Ken Levenson is an architect, Certified Passive House Consultant, President of the non-profit New York Passive House, a founder of the North American Passive House Network, an International Passive House Association Affiliate Council Member, and COO of 475 High Performance Building Supply.
 Building retrofits have slightly more lenient energy requirements for airtightness and energy demand.
 Treated Floor Area is not a typical gross or net calculation but a measure of the actual usable square footage as defined by PHI – typically about 10% smaller than gross.