Our last installment, What is a Passive House?, introduced the reasons behind the growing popularity of the Passive House movement. Now let’s address criteria for certification of new projects. There are three criteria that factor into earning certifications including:
- Air-tightness of the building envelope or shell.
- Annual total primary (or source) energy used by the building (Primary energy = Total energy used to produce the energy supplied to the building, which is known as secondary energy.)
- Annual energy needed to heat or cool the building to a comfortable temperature.
A newly constructed passive building can only leak 0.6 air changes per hour (ACH).
To compare, Northwest Energy Star requires 2.5 to 7.0 ACH. For a passive building, the primary, or source, energy does not exceed 38.1 kBtu per square foot per year, also known as the energy use intensity (EUI). The energy for heating or cooling does not exceed 4.75 kBtu per square foot per year.
Currently, two organizations certify buildings to the Passive House standard. Internationally, the Passivhaus Institute (PHI) has certified buildings throughout the world (including the U.S.) since 1993. PHI maintains a database of over 2,000 passive buildings. The non-profit Passive House Institute US (PHIUS) certifies passive houses in the United States. However, most passive buildings are not certified, and it is estimated that there are in excess of 30,000 buildings worldwide which meet the standard.
Portland currently has over 10 buildings meeting the standard, four of which are certified. In Oregon, there are approximately 20 passive buildings, including new and retrofitted commercial, multifamily, and single family residences. Recently, several homes were featured on the City of Portland Build It Green! Home Tour. In 2012, a couple’s compact Portland home was showcased.
Passive House Northwest is a support and advocacy trade organization with monthly meetings and annual conferences inSeattle andPortland.