PassivHaus Standards for N. America?
BuildingScience.com has just published an article by John Straube with a critical analysis of the relevance of PH standards for a North American climate:
Homes in cold climates (DOE Zones 5-7) that employ:
• minimum R-5:10:20:40:60 enclosure,
• 1.5 [email protected] airtightness or better,
• condensing (>95%) gas furnaces with ECM fan motors,
• right-sized (ASHRAE 62.2) efficient (> 65%, >1.5 cfm/W) HRV’s
• condensing (>92%) hotwater natural gas water heaters
• appliances in the top 10% of Energy Star combined with CFL lighting
deliver total energy and environmental performance that approaches the Passivhaus standard in cold climates. Such houses depart in relatively minor ways from standard North American construction, accommodate a broader range of architectural styles, can be modified easily for different climate zones, and can even be built by production builders.
Achieving the specific Passivhaus target of 15 kWh/m2/yr for heating on site energy use, results in investment of materials and money that often will exceed other less costly and environmentally impactive solutions. Achieving the equally arbitrary 120 kWh/m2/yr has more direct environmental benefits than the heating target, but may best (i.e., with least cost and environmental damage) be achieved using some on-site power generation.
As new clean, local, and renewable energy sources come on line over the next 25 years and become more affordable than current PV prices, it is unlikely that the extreme conservation measures taken by Passiv Haus to meet the specific requirements will be considered an optimal deployment of resources for cold climate housing.
From a point of view of the wise use of capital, the Passivhaus approach in cold-climate zones of North America can often lead to more expensive, less architecturally flexible, and even more energy intensive houses than a more flexible approach that focuses only on the least cost, most durable means of achieving a primary energy use per area target value. Perhaps the most important contribution made by the PH standard to low-energy North American housing is that one cannot simply buy $200,000 worth of PV panels to meet the target, as too many net zero homes have done.