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While the idea of a super-insulated, high-performance house began in North America in response to the 1973 energy crisis, interest in this concept declined in the United States and Canada in the following decades.[1] Subsequently, the concept picked up steam in the early 1900s and developed into Passivehaus in Germany. Passivehaus was designed to emphasize low energy use, health, comfort and resilient construction in a German climate, so when the concept regained popularity in the U.S. in the early 2000’s the German Passivehaus standards did not consider the multiple and varying climate zones of North America.
The first U.S. passive house was built in Urbana, Illinois in 2005.[2] Since then, only 90 or so homes have been certified as passive.[3] This small number of passive homes in the United States may be a result of the passive house standards developed in Germany for a German climate that is not translatable to the various climates in North America. A passive house built following the traditional requirements would meet the climate and economic needs of one area, but would not match the needs of the multiple climate and economic landscapes found in America. This is why passive building has taken off in the Pacific Northwest, where the climate is similar to a German climate, and not in the hot and humid South. To address this issue, members of the Passive House Institute US and the U.S. Department of Energy researched climate-specific passive building standards and published a summary of their findings in July. Transitioning to climate-specific standards will make passive houses more cost effective and will stimulate faster adoption in the United States.
Senior Scientist Graham Wright and his technical team at Passive House Institute US have created new climatological standards that address the three main pillars of Passive House Design: air tightness, energy source, and space conditioning.[4]The previous air tightness requirement of 0.6 ACH50 (air changes per hour at 50 Pascals pressure difference) changed to 0.05 CFM50 (cubic feet per minute of air flow at 50 Pascals pressure difference).[5] This change will better consider the scale of the building.
Regarding energy source changes, the new standard was altered in relation to the global carbon dioxide budget. In subcategories of the energy source standard, changes were made to more fairly and accurately calculate carbon dioxide emissions: requirements changed from a square foot limit to a per-person limit; lighting and miscellaneous plug load defaults increased to 80 percent of the RESNET default, better matching the U.S. average; and to offset the increase in lighting and plug load, the energy limit increased temporarily to 6,000 kWh per person per year. Lastly, the space conditioning standards were re-evaluated on economic viability. These requirements shifted to mandatory, climate-specific thresholds for annual heating and cooling loads, guaranteeing that efficiency measures will have a reasonable payback period in relation to energy savings.
Building science and environments are constantly changing and no one is like another. The new climate-specific standards are just one step in the process of constructing better buildings. The Passive House Institute US Technical Committee has made progress in making the Passive House movement more viable in the United States and has promised to continually re-visit these standards in order to lead the way towards zero-energy-ready homes.
[1] “Passive History in a Nutshell.” Passive History: Passive House Institute U.S. Passive House Alliance, 2015. Web. 19 Aug. 2015.
[2] Keenan, Sandy. “The Passive House: Sealed for Freshness.” The New York Times. The New York Times, 14 Aug. 2013. Web. 19 Aug. 2015.
[3] Ibid.
[4] “PHIUS+ 2015: Passive Building Standard — North America.” Passive House Institute. Passive House Alliance, 2015. Web. 19 Aug. 2015.
[5] Burks, Larry. “How Tight Is Tight Enough?” Up Hill House. WordPress, 25 Jan. 2011. Web. 20 Aug. 2015.