- Category: Topics
23 Aug 2011
- Published on Tuesday, 23 August 2011 21:24
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A passive house is a well-insulated, virtually air-tight building which has the ability to heat and cool itself, thus reducing energy consumption of the building by as much as 90 percent.
The term “passive house” comes from the German “passivhaus”, owing to the fact that the very first models of these types of construction emerged in Darmstadt, Germany, in 1990. These first passive multi-family houses attained energy consumption at less than 12 kilowatt hours per square meter area – equal to less than one-tenth of the average energy consumption in Germany.
The first passive house concept rose from discussions between professors Bo Adamson of Sweden’s Lund University and Wolfgang Feist. Mr. Feist established The Passive House Institute in 1996, a private organization which promotes, evaluates and maintains passive house constructions.
The institute and Mr. Feist worked with the European Union on the ‘Cost Efficient Passive Houses as European Standards’ (or CEPHEUS) research project, which validated the passive house standard as an energy efficient building standard for European constructions.
The institute outlines several points which a passive house construction has to fulfill. These points cover overall insulation, energy re-use, and the use of energy efficient appliances and fixtures. For example, specific requirements on the U-factor or heat loss rate of a house’s exterior shell or windows are indicated – set at not exceeding 0.15 watts-per-square-meter-per-kelvin [W/(m²K)] and 0.80 W/(m²K), respectively.
Air leakage through unsealed joints must be less than 0.6 times the house volume per hour to ensure air-tightness. Hot water must be provided by solar collectors or heat pumps. Fresh air must be pre-heat through underground ducts that exchange heat with the soil, reaching above 5 degrees Celsius, even on cold winter days. Electric appliances such as refrigerators, stoves, freezers, lamps, washers, and dryers must be low-energy.
Apart from adhering to established passive house standards, a passive house, in general, must not exceed the combined capitalized costs of an average new home, covering design, construction, equipment installation, and operating costs within 30 years.
Other passive house institutes have sprung in other countries, such as in Austria and the United States, all establishing standards that consider the climatic conditions on these places. For example, in the case of Florida, the cooling load becomes a major factor due to the state’s hot climate.
In California, the target for reducing energy consumption is set at 80 percent. All in all, despite the variations, the standards are approved under the supervision of the original, Germany-based institute.