Passive house
From Wikipedia, the free encyclopedia
The term Passive house (Passivhaus in German) refers to the rigorous, voluntary, Passivhaus standard for energy use in buildings. It results in ultra-low energy buildings that require little energy for space heating. A similar standard, MINERGIE-P®, is used in Switzerland [1].
The first Passivhaus buildings were built in Darmstadt, Germany, in 1990, and occupied the following year. In September 1996 the Passivhaus-Institut was founded in Darmstadt to promote and control the standard. Since then more than 6,000 Passivehaus buildings have been constructed [2] in Europe, most of them in Germany and Austria, with others in various contries world-wide.
Despite the name, the standard is not confined only to houses. Several office buildings, schools, kindergartens and a supermarket have also been constructed to the standard. Although it is mostly applied to new buildings, it has also been used for refurbishments.
Contents |
[edit] The standard
The Passivhaus standard requires that the building is within the following limits [3]:
- The building must not use more than ≤ 15 kWh/m²a (4,755 Btu/ft²/yr) in heating energy
- The specific heat load for the heating source at design temperature must be less than 10 W/m²
- With the building pressurised to 50Pa by a blower door, the building must not leak more air than 0.6 times the house volume per hour (n50 ≤ 0.6/h).
- Total primary energy consumption (primary energy for heating, hot water and electricity) must not be more than 120 kWh/(m²a) (38,039 Btu/ft²/yr)
These standards are much higher than houses built to most normal building codes. For comparisons, see the international comparions section below.
National partners within the 'consortium for the Promotion of European Passive Houses' (PEP) are thought to have some flexibility to adapt these limits locally.
[edit] Space heating requirement
By achieving the Passivhaus standards, Passivhaus buildings are able to dispense with conventional heating systems. The ability to do this is the underlying Passivhaus objective. However this does not mean that no heating is required, and most Passivhaus buildings do include a system to provide low levels of supplemental space heating. This is normally distributed through the low-volume heat recovery ventilation system that is required to maintain air quality, rather than by a conventional hydronic or high-volume forced-air heating system, as described in the space heating section below.
[edit] Construction costs
In Passivhaus buidings, the cost savings from dispensing with the conventional heating system can be used to fund the upgrade of the building envelope and the heat recovery ventilation system. With careful design and increasing competition in the supply of the specifically designed Passivhaus building products, in Germany it is now possible to construct buildings for the same cost as those built to normal German building standards, as was done with the Passivhaus apartments at Vauban, Freiburg [4].
Evaluations have indicated that while it is technically possible, the costs of meeting the Passivhaus standard increase significantly when building in northern Scandinavia above 60° latitude [5] [6].
[edit] Design and construction
Achieving the major decrease in heating energy consumption required by the standard involves a shift in approach to building design and construction. Design is carried out with the aid of the 'Passivhaus Planning Package' (PHPP) [7], and uses specifically designed computer simulations.
To achieve the standards, a number of techniques and technologies are used in combination:
[edit] Passive solar design
Following passive solar building design techniques, where possible buildings are compact in shape to reduce their surface area, with windows oriented towards the south (in the northern hemisphere) to maximise passive solar gain. However the use of solar gain is secondary to minimising the overall energy requirements.
Passive houses can be constructed from dense or lightweight materials, but some internal thermal mass is normally incorporated to reduce summer peak temperatures, maintain stable winter temperatures, and prevent possible over-heating in spring or autumn before normal solar shading becomes effective.
[edit] Superinsulation
Passivhaus buildings employ superinsulation to significantly reduce the heat leakage through the walls, roof and floor compared to conventional buildings. A wide range of thermal insulation materials can be used to provide the required high R-values (low U-values, typically in the 0.10 to 0.15 W/m2K range). Special attention is given to eliminating thermal bridges.
A disadvantage resulting from the thickness of wall insulation required is that, unless the external dimensions of the building can be enlarged to compensate, the internal floor area of the building may be less compared to traditional construction.
[edit] Advanced window technology
To meet the requirements of the Passivhaus standard windows are manufactured with exceptionally high R-values (low U-values, typically 0.85 to 0.70 W/m²K for the entire window including the frame). These normally combine triple-pane insulated glazing (with a good solar heat-gain coefficient, low-emissivity coatings, argon or krypton gas fill, and 'warm edge' insulating glass spacers) with air-seals and specially developed thermally-broken window frames.
In Central Europe, for unobstructed south-facing Passivhaus windows, the heat gains from the sun are, on average, greater than the heat losses, even in mid-winter.
[edit] Airtightness
The standard requires the building to achieve very high levels of airtightness, much higher than are normally achieved in conventional construction. Air barriers, careful sealing of every construction joint in the building envelope, and sealing of all service penetrations through it are all used to achieve this.
Airtightness minimises the amount of warm (or cool) air that can pass through the structure, enabling the mechanical ventilation system to recover the heat before discharging the air externally.
[edit] Ventilation
Mechanical heat recovery ventilation systems, with a heat recovery rate of over 80% and high efficiency ECM motors, are employed to maintain air quality. Since the building is essentially airtight, the rate of air change can be optimised and carefully controlled at about 0.4 air-changes per hour. All ventilation ducts are insulated and sealed for air tightness.
Although not compulsory, earth warming tubes (typically ≈20cm diameter, ≈40 m long at a depth of ≈1.5 m) are often buried in the soil to act as earth-to-air heat exchangers and pre-heat (or pre-cool) the intake air for the ventilation system. In cold weather the warmed air also prevents ice formation in the heat recovery system's heat exchanger.
[edit] Space heating
In addition to using passive solar gain, Passivhaus buildings make extensive use of their intrinsic heat from internal sources – such as waste heat from lighting, white goods (major appliances) and other electrical devices (but not dedicated heaters) – as well as body heat from the people and animals inside the building. Together with the comprehensive energy conservation measures taken this means that a conventional central heating system is not necessary, although they are sometimes used due to client preference.
Instead, Passive houses typically have a dual purpose 800 to 1,500 Watt heating and/or cooling element integrated with the supply air duct of the ventilation system. It is fundamental to the design that all the heat required can be transported by the normal low air volume required for ventilation. A maximum air temperature of 50°C (122°F) is applied to prevent any possible smell of scorching from dust that escapes the filters in the system.
The air-heating element can be heated by a small heat pump, by solar thermal energy, or simply by a natural gas or oil burner. In some cases a micro-heat pump is used to extract additional heat from the exhaust ventilation air, using it to heat either the incoming air or the hot water storage tank. Small wood-burning stoves can also be used to heat the water tank, although care is required to ensure that the room in which stove is located does not overheat.
Because the heating capacity and the heating energy required by a passive house both are very low, the particular energy source selected has fewer financial implications than in a traditional building, although renewable energy sources are well suited to such low loads.
[edit] Lighting and electrical appliances
To minimise the total primary energy consumption, low-energy lighting (such as compact fluorescent lamps), and high efficiency electrical appliances are normally used.
[edit] International comparisons
- In the United States the standard results in a building that requires space heating energy of 1 BTU per square foot per heating degree day, compared with about 5 to 15 BTUs per square foot per heating degree day for a similar building built to meet the 2003 Model Energy Efficiency Code. This is between 75 to 95% less energy for space heating and cooling than current new buildings that meet today's US energy efficiency codes.
- In the United Kingdom, an average new house built to the Passive House standard would use 77% less energy for space heating compared to the (2002?) Building Regulations [8].
- In Ireland, it is calculated that a typical house built to the Passive House standard instead of the 2002 Building Regulations would consume 85% less energy for space heating and cut space-heating related carbon emissions by 94% [9].
[edit] Origins of the passive house
The Passive House standard originated from a conversation in May 1988 between Professors Bo Adamson of Lund University, Sweden, and Wolfgang Feist. Their concept was developed through a number of research projects, aided by financial assistance from the German state of Hessen. The eventual building of four row houses (terraced houses) was designed for four private clients by professors and architects Bott, Ridder and Westermeyer.
After the concept had been validated at Darmstadt, with space heating 90% less than required for a standard new building of the time, the 'Economical Passive Houses Working Group' was created in 1996. This developed the planning package and initiated the production of the novel components that had been used, notably the windows and the high-efficiency ventilation systems.
The products developed were further commercialised during and following the European Union sponsored CEPHEUS project, which proved the concept in 5 European countries over the winter of 2000-2001.
While some techniques and technologies were specifically developed for the standard, others (such as superinsulation) were already in existence, and the concepts of passive solar building design dates back to antiquity. There was also experience from other low-energy building standards, notably the German Niedrigenergiehaus (low-energy house) standard, as well as from buildings constructed to the demanding energy codes of Sweden and Denmark.
[edit] Comparison with zero energy buildings
A net zero energy building (ZEB) is another term for a very similar approach to creating small buildings that use substantially less energy. Zero energy building or zero energy home seem to be phrases that are gaining popularity in the United States, possibly due to the implication that the energy for a zero energy home would be free.
Unfortunately the ZEB seems to have been implemented without making maximum use of passive techniques to minimise heat loss and instead relies on active techniques to make up the energy / heat shortfall. See zero energy building for details of the debate.
[edit] See also
- CEPHEUS
- Energy-plus buildings
- Low-energy buildings
- Self-sufficient homes
- Thermal conductivity for an explanation of how thermal conductivity, thermal conductance, and thermal resistance are related
[edit] External links
[edit] Official Passive House organisations
- Passive House Institute Darmstadt, Germany
- PassivHausUK The official United Kingdom Web site.
- Consortium for the Promotion of European Passive Houses (PEPH)
[edit] Passive House research
- Passive House Estate in Hannover-Kronsberg Construction details and performance
- CEPHEUS Final Report Major European Union research project. Technical report on as-built thermal performance.
- "Passive-On Project" Research and dissemination to promote Passive Houses in warm climates.
[edit] Passive House examples
[edit] Domestic
- The original Darmstadt Passive Houses
- German & Austrian residential Passive House examples
- Kama House One of the first Passive Houses in the United Kingdom.
- Passive House, Ireland
- Waldsee The first certified US Passive House (Minnesota).
- E-colab Passive House projects, Urbana, Illinois
[edit] Non-domestic
- Nah&Frisch Passivhaus supermarket In German, with photos.
- Energon Passivhaus office building In German, with photos
- ChristophorusHouse multifunctional office / warehouse / cultural building, Austria
- Passive Geothermal Warehouse, Illinois
[edit] Other links
- History of the Passivhaus In German
- IEA Energy Conservation in Buildings and Community Systems Programme
| Energy and Conservation Edit | |
|---|---|
| Energy conservation | Energy-efficient landscaping | Passive house | Passive solar building design | Superinsulation | Simple living | Ecological footprint | Ecovillage | Waste | Zero energy building | |
 |
|
|||
