Passive House Construction – What is it?

Passive House construction has come to the Pacific Northwest. It is a very energy-efficient and environmentally conscious building method that has been in use in Europe with more than 15,000 buildings built or retrofit to its standards over the last decade.  A few Passive houses have been built in the United States, with some projects already started in Oregon, but a project in Seattle has just broken ground on what is hoped to be the first certified project here.

The driving force behind the Passive House movement has been to significantly reduce the energy required to heat and operate a house or other building while still maintaining a comfortable & healthful environment that is also affordable.  Passive House is not a specific type of building like straw bale or earth sheltered.  It can be built with normal stick frame construction, or Structurally Insulated Panels, or some other method, as long as that method meets the prescribed requirements of Passive House.  This gives designers and builders leeway to explore new methods.  Physics will be what limits the choices ultimately, but there is help.  A software planning package is available to model projects before they are built to give the best representation of what can be expected once the project is built.

There are only a few Passive House requirements to be met, but they are strict.

  • The project must use no more than 15kwh/m2/yr for heating.
  • There is a limit of 120kwh/m2/yr for primary energy sources including heating, hot water, & electricity.
  • The project must pass a blower door test of .6ACH @50 pascal pressure

As a way to relate this to a traditional house that can use 160kw/m2/yr for heating (or more), you can see that Passive House aims to be about 90% more efficient.  So how is this accomplished?  If new construction, the house can be sited in such a way as to take advantage of natural solar heating and daylighting.  If existing construction, those options can still be utilized, but in a more limited fashion.  Window sizes can be increased or decreased, shading devices can be employed, or materials chosen to enhance what is already in existence.  In either case, the design will take into consideration the local weather patterns, the occupancy patterns expected, and materials used.  The construction will include an airtight barrier that will necessitate the need for artificial ventilation and that ventilation will also recapture heat from the exhaust air to be kept within the building to be as energy efficient as possible.

All sources of heat, from appliances, to solar gain, to people are considered in the design of a Passive House.  In some climates it might be possible to not have a heating source at all, but generally there is a small one – so small that it could use the same energy requirements as a hand held hair dryer.  In some areas cooling is the more critical concern to homeowners and a Passive House can be designed to keep its occupants comfortable year round no matter what the climate.  The goal is to have an average inside temperature of 68 degF.  That might sound a bit cool, but people who have lived in these houses find the draft free construction makes that temperature quite pleasant.  The key lies in the planning, the insulation and other materials chosen, and the strict adherence to airtight construction.

This past Friday, a project by Dan Whitmore of Blackbird Builders llc broke ground for what is hoped to be the first Certified Passive House in Seattle.  I met Dan while attending the Certified Passive House Consultants training (which we both passed) and he has been gracious enough to allow me to follow his project on this blog as it progresses.  I plan to take pictures of the different phases and point out where the Passive House features come into play.  If you would like to follow along with this blog, please sign up for the email updates on the right side of the page.  Feel free to post comments or ask questions.

Additional Information on Passive House Construction:

http://passivehouse.us/passiveHouse/PassiveHouseInfo.html

http://www.passiv.de/English/PassiveH.HTM

http://phnw.org

–Linda

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