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Report 4 of 5:
The
Cepheus Complex - Austria
Introduction
A Passive House is a building with an extremely low heating energy demand. The term "Passive House" refers to a construction standard. The standard can be met using a variety of technologies, designs and materials. It is a refinement of the low-energy house (LEH) standard. The Passive House standard offers high comfort, minimal energy consumption and negligible heating costs.
Cepheus (Cost Efficient Passive Houses as European Standards) is a five year project which started in 1997 and is funded by the European Commission. It has been implemented in five European countries to encourage architects and designers to build affordable, energy efficient houses. The Cepheus project demonstrates that low energy demand can be achieved at different European sites, by different constructions at the same cost as for conventional buildings.
Passive House technologies
The Passive House offers a cost-efficient way of minimising the energy demand of new buildings in accordance with the global principle of sustainability, while at the same time improving the comfort experienced by the building occupants.
Passive Houses are buildings in which a comfortable indoor climate can be achieved in summer and in winter without needing a conventional heating or air conditioning system. A separate heating system is not necessary because heating energy can be distributed in the building by means of the existing ventilation system. The total energy demand of a passive house is equal to the electricity demand of a conventional dwelling.
The heat inputs are delivered externally by solar radiation through the windows and internally by the heat emissions of appliances and occupants. These inputs are essentially sufficient to keep the building at a comfortable indoor temperature throughout the heating period. The minimal heat requirement can be supplied by heating the supply air in the ventilation system – a system which is necessary in all housing.
Efficient technologies are also used to minimise the other sources of energy consumption in the building, most notably electricity for household appliances. The total final energy consumption for space heating, domestic hot water and household appliances of a Passive House is lower by at least a factor of 4 than the specific consumption levels of new buildings designed to the standards presently applicable across Europe.
Passive solar gain
South-facing Passive Houses are also solar houses. The passive gain of incoming solar energy through window glazing dimensioned to provide sufficient daylight covers about 40% of the minimised heat losses of the house. The houses have high insulation through the use of improved windows with high quality glass and frames which are air tight. The triple glazing and superinsulated frames let in more solar heat than they lose. Argon is the filling material between the layers of glass and there is a special wooden frame construction which has some ventilation between the wooden outside and the wooden inside of the frame. The benefit can be enhanced if the main glazing areas are oriented to the south and are not shaded.
Superinsulation
Passive Houses have an exceptionally good thermal envelope, preventing thermal bridging and air leakage. To be able to dispense with an active heating system while maintaining high levels of occupant comfort, it is essential to observe certain minimum requirements upon insulation quality.
Combining efficient heat recovery with supplementary supply air heating
Passive Houses have a continuous supply of fresh air, optimised to ensure occupant comfort. The flow is regulated to deliver precisely the quantity required for excellent indoor air quality. A high performance heat exchanger is used to transfer the heat contained in the vented indoor air to the incoming fresh air. The two air flows are not mixed. On particularly cold days, the supply air can receive supplementary heating when required. Additional fresh air preheating in a subsoil heat exchanger is possible, which further reduces the need for supplementary air heating.
Electric efficiency means efficient appliances
By fitting the Passive Houses with efficient household appliances, hot water connections for washing machines and dishwashers, airing cabinets and compact fluorescent lamps, electricity consumption is also dramatically reduced. Energy savings of up to 50% compared to the average housing stock can be achieved without any loss of comfort or convenience. All building services are designed to operate with maximum efficiency. High-efficiency appliances are often no more expensive than average ones but as a rule, they pay for themselves through electricity savings.
Meeting the remaining energy demand with renewables
Cost-optimised solar thermal systems can meet between 40 and 60% of the entire low-temperature heat demand of a Passive House. The remaining energy consumption (for space heating, domestic hot water and household electricity) can be offset completely by the use of renewable sources, making the Passive House fully primary-energy and climate neutral.
Principles of Passive Housing
What makes the approach so cost-efficient is that it relies on optimising those components of a building which are necessary in every case, for example, the windows and the automatic ventilation system. Improving the efficiency of these components to the point at which a separate heat delivery system can be dispensed with, yields the savings which largely finance the extra costs of improvement.
Passive houses can be built cost-efficiently. The total costs (including investments in the building, such as planning and building services, plus running costs over a period of 30 years) in a Passive House are no higher than for an average new building.
Benefits of passive energy saving technologies
No further elements are required in addition to a conventional building. It is only necessary to construct the components that are used in any case, such as floors, outer walls, windows, roofs and ventilation, to better quality standards than usual. Over the medium term, such a quality improvement need not cause higher investment costs than in a standard house. Particularly through the prefabrication of high quality exterior building elements such components can be produced very cost effectively.
A passive house is an ordinary low energy house but it uses about 80% less heating energy than new buildings.
Cepheus strategic objectives
CEPHEUS – a project involving the construction and scientific evaluation of 250 housing units built to Passive House standards in five European countries – has set itself the following goals:
To demonstrate the technical feasibility (in terms of achieving the targeted energy performance indexes) and cost effectiveness for an array of different buildings and designs implemented by architects and developers in a variety of European countries;
To study investor-purchaser acceptance and user behaviour under real-world conditions for a representative range of buildings;
To test the implementation of the Passive House quality standard throughout Europe with regard to cost-efficient planning and construction;
To provide opportunities for both the lay and the expert public to experience the Passive House standard hands-on at several sites in Europe;
To give development impulses for the design of energy- and cost-efficient buildings and for the further development and accelerated market introduction of individual, innovative technologies compliant with Passive House standards;
To create the preconditions for broad market introduction of cost-efficient Passive Houses;
To illustrate the potential of the Passive House standard to provide a basis on which it is possible to meet the energy requirements of new housing in a manner that is both cost-efficient and, in sum over the whole year, produces zero greenhouse gas emissions (climate neutrality criterion).
ITDG would like to thank the CEPHEUS project and the energy institute for providing the original material on the cost efficient passive houses.
For further information, please contact:
This document is an output from a project funded by the UK Department for International Development (DFID) for the benefit of developing countries. The views expressed are not necessarily those of the DFID.
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