Sustainable Building -Passive House

Passive House

The term ‘Passive House’ is a relatively recent buzzword amongst sustainable building enthusiasts and refers to a demanding voluntary standard of energy efficiency in buildings, with the aim of reducing ecological footprints and promoting sustainable buildings. The idea is to construct ultra low energy use buildings which require little power to maintain acceptable temperatures. The term Passive House was first used in Germany (Passivhaus)but a similar sustainable building standard is used in Switzerland (MINERGIE-P). The idea is not confined to residential properties.

sustainable building

Similar sustainable building standards have been applied to supermarkets, kindergartens, schools, and office buildings on the continent. It may come as a surprise to some British consumers that our energy prices are lower than those on the continent. Added to that fact Northern Continental Europe suffers much colder winters than we do has resulted in the drive for sustainable building having gone hand in hand with the need to cut energy costs for far longer than it has here. Sustainable building is in its infancy in the UK and what has been achieved to date is often misguided. The main fact to be understood however is that, a ‘Passive House’ design, is not a supplement to architectural design. It’s intrinsic to the building process itself and is the negation of the ‘eco bling’ concept of retro fitting and the placing add ons in the hope of creating new sustainable buildings from old unsustainable ones In some instances however it is possible to create a Passive House by way of a refurbishmentbut it’s nevertheless a difficult task. The way to create a Passive House is to construct it as a sustainable building. It may even be best to demolish a structure and reconstruct it as a sustainable building from scratch

Most Passive House structures built to date have been in Scandinavia and German speaking countries where sustainable building considerations have been higher up the agenda for decades. By the end of 2010 about 25,000 had been built in Europe but only 13 in the USA. This again reflects the relative prices of energy and (to a lesser extent) climate. The Passive House standard originated in 1988 in sustainable building discussions involving Bo Adamson of Lund University in Sweden and Wolfgang Feist of the German Institute for Housing and the Environment and the idea was developed using funding assistance provided by the German State of Hessen as part of its general commitment to promoting sustainable building standards. The first examples of this new vision of sustainable building were constructed by architects Bott Ridder and Westermeyer in Darmstadt Germany in 1990. The contracts were with private clients all of whom moved in the following year. By 1996 the Passivhaus Institute was founded in Darmstadt to promote and set the standards. The sustainable building criteria are a demanding ones. A standard of 90% less energy required for use for heating compared with a conventional building is required.. The ‘Economical Passive Houses Working Group’ was set up which developed the planning package and promoted the production of the innovative components designed with sustainable building projects in mind. In particular windows with high efficiency ventilation systems are indispensable to the design. Later the EU as part of its programs for promoting sustainable building sponsored the CEPHEUS project which by 2000-2001 had proved the concept in five European Countries. The first Passive House in the USA was built in 2006 in Bemidji Minnesota. A company called Scandinavia Homes built the first Passive House in Ireland in 2005 and has since built a number in the UK and Poland. The largest Passive House Project at the moment is the Bahnstadt Project in Germany and a company in Qatar is building the first Passive House in the Middle East

Passive House Sustainability Building Standards and Design

  • The house must be constructed to annual heating requirement of not more than 15 kWh/m²  (4746 btu/ft² ) for heating and 15 kWh/m² for cooling or with a peak heat requirement of 10W/m²
  • Total annual primary energy consumption must be no more than 120 kWh/m² per year (3.79 × 104 btu/ft² per year)
  • The building must not leak more than 60% of the house air volume per hour (n50 ≤ 0.6 / hour) at 50 Pa (N/m²)
  • Although not a requirement it is recommended that the specific heat load for the heating source, be less than 10 W/m² (3.17 btu/h.ft² per hour)

There is some flexibility to vary these requirements from locality to locality

Insulated and sealed ready for plaster boarding

Insulated and sealed ready for plaster boarding

If these sustainable building standards are achieved conventional space heating should not be required, although low volume heat recovery systems are incorporated in Passive Houses to maintain air quality. Passive Solar Building Design and energy efficient landscaping are incorporated into the holistic sustainable building design. Buildings are typically compact in shape with the windows oriented towards the South in the Northern Hemisphere. This enhances solar gain although the main principle behind the design of the house is to promote sustainable building performance by minimizing energy consumption. In climates where the aim is to reduce heat gain various other techniques are implemented. The use of deciduous trees can help in seasonal temperature control and different reflective surfaces supplement the effect. The main seasonal stabilization effect however is achieved by incorporating as much internal thermal mass as possible to keep the property cool in the Summer and Warm in the Winter

Passive House buildings incorporate super insulationto reduce heat loss through the roof, walls, and floor and special attention is given to avoiding thermal bridges. But one disadvantage which arises is that the internal floor area is reduced owing to the thickness of the walls. Sustainable building innovations in the form of Advanced Window Technology incorporating thermally broken window frames and air seals achieve the necessary standards in the windows, and in Central Europe South Facing advanced windows can achieve more heat gain than loss even in Winter. Passive Houses have to be extremely airtight to maintain their sustainable building credentials and the design ensures that most of the air exchange with the outside goes via heat exchangers which also assist in the management of moisture and dew points. All construction joints in the building have to be sealed. Some Passive House Builders favour the use of earth warming tubes which are buried in the soil to act as earth to air heat exchangers which can pre heat the air intake for the ventilation system. In cold weather the warmed air prevents ice formation in the heat recovery system’s heat exchanger, although in some climates condensation and mould can arise. So an alternative to achieve the Passive House sustainable building criteria is an earth to air heat exchanger which uses a liquid circuit instead of an air circuit with a battery on the supply side

More insulation the better

More insulation the better

Costs

Typically Passive House construction can be as much as 10-15% more expensive than conventional, non sustainable building orientated techniques but recent innovations in Germany have made it possible to achieve construction costs which match conventional houses. This represents very significant long terms savings in costs of occupancy. Apart from the energy cost savings arising from their sustainable building techniques, Passive Houses require less maintenance and are more solidly built. Some traditional modern constructions can be comparatively flimsy. Recent evaluations have found that costs of meeting the Passive House Sustainable Building Standard in construction rises significantly at 60 Degree Latitude in Europe. By way of an example the UK is at 51 Degrees and Moscow at 55 Degrees. But the cost of heating also has to be factored into the equation. The highest latitudes also have the coldest climates. which largely explains why sustainable building is most advanced in Scandinavia and Canada. These considerations have encouraged designers to construct buildings which use the ground under the structure for large scale heat storage which allow heat stored in the Summer to be used in the Winter and the reverse process for seasonal cooling. A cheap solution has recently been developed using a passive thermo siphon using only air