The not-so-little differences? A transatlantic divide over Passive House standards.

It isn’t just the Royale with Cheese, as famously quoted by Vincent Vega in Pulp Fiction, that seems to be dividing Europeans and Americans. Beyond the obvious examples of language, government and traffic rules, the transatlantic divide will soon appear in yet another field – this time in the certification of optimum energy-efficient passive houses.

The first passive house, built in Darmstadt, Germany, in 1991, has a maximum heat load of 7.4W/m² and is currently still in use. Leading to a wave of new passive housing developments in subsequent decades, these houses are kept ‘passive’ by using existing internal heat sources, solar energy and the minimal heating of incoming fresh air.

The Darmstadt-based Passivhaus Institut (PHI) continues to monitor buildings, ensuring that measured energy consumption for heating remains below 15kWh/m² per year and total primary energy consumption is below 120kWh/m² while not leaking more air than 0.6 times the house volume per hour, thus guaranteeing comfortable indoor temperature without a conventional heating system.

Over 15,000 passive houses have been built in Germany alone, while 17% of all new single-house projects in Austria are passive houses.

Widely diverse in architecture and design, passive houses have gained popularity due to their ability to save up to 85% more on energy bills than regular constructions and for their creative use of materials. The first polyurethane-insulated house in Belgium for example, is being constructed in Evere.

PHI standards officially arrived in the US in the late 2000s. However, the shaky alliance between PHI and its North American affiliate, the Passive House Institute US (PHIUS), was short-lived and came to an official end in August 2011.

New PHIUS standards will diverge from PHI by allowing additional annual peak load allowances, space conditioning requirements, source energy requirements as well as airtightness criteria based on climatic zones. PHIUS has also announced it will work closely with the HERS index (the Home Energy Rating Standard developed by the Residential Energy Services Network, RESNET), under which energy performance is rated on an index of zero to 100, i.e. from a house that requires zero energy on an annual basis to a home complying with current US building standards.

What will this mean for the future of passive houses in Europe and the US? Until the specifics of the PHIUS proposal are published, the only fact that remains clear is that all housing that has already received PHI certification in the US will remain certified. Let’s wait until the full PHIUS proposal is published before mid-2012 to see whether or not the transatlantic divide deepens even further. One can only hope that both sides’ commitments to improving energy efficiency in buildings will only seriously diverge over metric measurements rather than content.

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