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What is a Passive House?

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Known in Germanyas Passivhaus (“passive building”), the passive house standard is the world’s most stringent set of building standards for energy efficiency. This concept and approach can be applied to all types of buildings in every climate. Passive buildings typically consume 30 to 50 percent less energy than a building constructed to current U.S. building codes.

A NE Portland Passive House under construction withlarge PV array and south-facing windowsConcept

The concept is to reduce energy consumption and carbon emissions by creating buildings which leak so little heat that “passive” heat gains (from solar, occupant body heat, lighting, equipment, appliances, etc.) ensure occupant comfort with “micro” heating systems.

Approach

The building envelope’s thermal performance is rigorously improved. Based on experience, the Passivhaus Institute has developed several guidelines. Since the standard is performance-based  instead of a prescriptive standard, designers and builders have responded with widely-varied designs, materials and envelope assemblies.

Passive buildings feature:

  • Super-insulated building envelope or shell.
  • High-performance windows.
  • Airtight construction.
  • Balanced, continuous mechanical ventilation typically with heat-recovery ventilation (HRV or ERV.)
  • Solar gain optimization by building and glazing orientation.   
  • Elimination or reduction of thermal bridging through the building envelope.
  • Energy-efficient mechanical systems, appliances, and lighting. 

A waste head recovery coil from drain waterThe Standard

There are three criteria that factor into earning certifications including:  

  1. Air-tightness of the building envelope or shell.
  2. Annual total primary, or source, energy used by the building (Primary energy = Total energy used to produce the site, or secondary, energy supplied to the building.)
  3. Annual energy needed for specific building area for heating or cooling to 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.

HRV DiagramPortland currently has over 10 buildings meeting the standard, and four are certified. In Oregon there are approximately 20 passive buildings including new and retrofitted commercial, multi-family, and single family residences. Recently, several homes have been featured on the annual City of Portland Build It Green! Home Tour. In 2012, a couple’s compact Portland home was showcased.

Learn More

Passive House Northwest is a support and advocacy trade organization with monthly meetings and annual conferences in Seattle and Portland. PHnw’s annual conference is March 15, 2013 in Seattle. 

 


 

Save the date!

 

The World’s Most Energy-Efficient Buildings

Wednesday, March 13th from 1:30 p.m.-3 p.m.

Portland Building, Room C, 2nd floor

1120 SW 5th Avenue

“Exemplary Buildings: Success Stories from Brussels, Belgium”

Guest Speaker: Ms. J.O. Dockx of Brussels Institute for Management of the Environment (“Brussels Environment).

How did a Portland-sized urban center launch an energy-efficient building program that helped cut regional energy consumption by 10 percent while maintaining economic viability? Through a combination of measures, Brussels has accomplished this goal.

In fact, Brusselsis already in alignment with the European energy goals for 2020 and 2050. Last year, the European Commission recognized Brussels Environment with the European Energy Award.

Ms. Dockx will explain how Brussels has created a government-private Exemplary Buildings partnership promoting ultra low-energy new construction and retrofits of commercial, institutional, multi-family, and single family residential buildings.

Since 2007, Brussels Environment has assisted 52 Exemplary Building projects with another 44 under construction (collectively, over 1.5 million square feet meeting the stringent Passive House standard for low-energy buildings).