What is passivhaus?
The term Passivhaus (or Passive House) refers to an advanced low energy construction standard for buildings providing excellent health and comfort conditions being both cool in summer and warm in winter with minimal heating or cooling requirements. The very high standard of construction needed to build a certified Passivhaus means that common building faults are avoided. Passivhaus buildings are designed for long life and high performance.
Passivhaus buildings provide a plentiful supply of fresh air internally to ensure low C02 levels whatever the season, and to provide perfect air humidity levels for healthy conditions all year round. Passivhaus buildings have fully openable windows, but provide excellent winter ventilation without wasting heat, and without cold winter draughts. In the summer the Passivhaus is ventilated by opening the windows but in winter to save energy, ventilation is normally achieved by a low-energy heat recovery ventilation system. The extremely low energy consumption of a Passivhaus often results in cost savings to the occupier of a Passivhaus building of more than 90% per year compared to ordinary buildings.
Passivhaus is an approach to building, defined by physicist Wolfgang Feist, that requires a high level of insulation and a draught-free construction, and, to maintain a flow of fresh air when windows are mostly closed in the cold winter months, an efficient heat recovery ventilation system. This uses very little energy, whilst saving a lot of energy that would otherwise go to waste. By concentrating on fabric-first measures to reduce energy consumption, alternatives to fossil fuels become possible, meaning that zero-carbon building is relatively easily achievable.
Passivhaus buildings save the cost of a conventional heating system and by this means, can now be built for little or no additional cost compared to ordinary buildings. Driving down the cost of passivhaus buildings is a major focus of research at bere:architects.
The Passivhaus approach can be explained briefly under the following headings:
Insulation - Super-insulated walls, floors and roofs create an affordable, comfortable and healthy environment. Insulation keeps winter warmth inside the building and is also used to protect the interiors from the hot summer sun. In addition, low energy demands make the use of renewable energy supplies a realistic alternative to fossil fuel.
Avoiding thermal bridges - It is essential to avoid all thermal bridging in the structure and fabric of a high quality building, in accordance with the Passivhaus design standard. With attention to details, condensation is prevented and heat losses are reduced by such a degree that a conventional heating system can be eliminated.
- Achieving draught free construction - We assist contractors to rigorously apply advanced construction techniques and testing. A high performance vapour control layer is essential for a number of reasons in addition to user comfort. Not least is that a leaky structure leads to condensation in the gaps, which leads to structural damage and reduced building life; as well as wasted money and energy .
Heat recovery ventilation - Our draught-free buildings improve air quality, firstly by using non-polluting natural materials, and secondly by using low-energy heat recovery ventilation systems to provide a continuous supply of fresh air warmed in winter by the air exhaled from the building. A high performance unit saves 90% of winter warmth and in the case of a domestic house, runs on only 15 watts of power on supply, and 15 watts of power on extract. Some units are designed to work on extract only in the summer months. Typically a high quality heat recovery ventilation unit saves 10 times more energy than it uses.
Solar energy - A passivhaus building will first and foremost derive a large proportion of its very low energy requirements passively from solar gains and internal heat gains, using external blinds to provide shading when this is not needed. However, in addition, a significant proportion of its water heating and electrical requirements can be derived from solar energy.
Summer comfort - In addition to insulating the interiors of a building from solar heat gains, automated solar shading will help avoid overheating in the summer. Night time natural fresh air circulation to purge-cool a little thermal mass will further improve comfort in summer months.
Water and health - We promote the advantages of the filtration of bathing and drinking water and install filtration systems in most of our buildings.
Rain water - Rain water is stored in underground tanks for use in the building. This reduces the risk of storm water flooding. Where space permits, we also use the natural cleansing of a reed bed to provide further protection to the environment.
Passivhaus demands a particular approach to design and construction, and requires a strong team spirit and rigorous on-site testing during the building process. At bere:architects we believe that the architect has a responsibility to help the contractor achieve the necessary standards. So in addition to providing intelligent, helpful, buildable designs, we provide all the construction team training that is required to achieve a successfully certified passivhaus. We often provide this training in association with partner organisations.
There are thousands of Passivhaus buildings in Germany, Austria and Belgium. The UK construction industry is fast adapting to increased knowledge of the standard. A growing number of stakeholders within the construction industry are realising the benefits of aiming towards and achieving the standard.
The UK government's Zero Carbon Taskforce has indicated that their 'Spec D' house, labelled 'Passivhaus equivalent', is likely to emerge as the best way for the UK construction industry to achieve its carbon reduction obligations by means of the 2016 minimum standard building codes. More on Passivhaus and 2016 Carbon Compliance will be found in a research paper published by bere:architects in the 'Research' section of this website.
If you would like answers to more detailed questions, visit http://passipedia.passiv.de/passipedia_en/