Both the terms 'passivhaus' and 'passive house' refer to the voluntary low-energy construction standard developed in Germany approximately 15 - 20 years ago, with the first monitored passivhaus being constructed in Darmstadt, Germany, in 1990.
The Passivhaus construction concept is a voluntary low-energy standard which is based on a set of identifiable and empirical criteria that a building can be measured against. The standard is not legally protected, and so although theoretically any building can claim to be a 'passivhaus' only those that are Certified are verified by the Passivhaus Institute and confirmed as such.
Passivhuas buildings are defined as those that have an extremely low energy demand and yet meet high standards for thermal comfort and good indoor air quality, even in very cold winters (down to -10 degrees C). The word 'passive' is used because the aim is to eliminate the need for an 'active' heating system: these buildings utilise the internal heat gains and solar energy entering through the glazed windows and doors, and minimally heat the incoming fresh air, in order to reduce the heating energy demand to it's minimum level for the design in a given geographical location. A 'fabric first' approach is adopted: there is no compensation available by relying on so called 'bolt-on' technologies in order to obtain a good energy 'rating' - the building itself must perform to a very high standard before any such things are added.
There are 6 main principles of passivhaus design which are based on the technical criteria that must be met in any certified building. The principles are:
Super insulation of the building envelope: all opaque elements of the external construction i.e. the ground floor, external walls and the roof, must be designed to limit the heat loss to a much higher standard than the current building regulations in the UK, and must be of a thermal bridge free construction.
High performance glazing: this will typically mean triple glazed windows and doors with low-E coatings, a warm edge spacer where the glass meets the frame, and a cross-laminated and / or insulated timber window frame.
A high level of airtightness: the thermal envelope should be enclosed by one continuous airtightness layer.
A good quality of indoor air: all spaces should be ventilated via a mechanical ventilation unit with heat recovery (MVHR) with a specified electrical and heat efficiency.
All electrical consumption within the building is considered and reduced by the use of efficient appliances.
- The glazing arrangement is designed to maximise the available solar gains, and reduce the risk of overheating during times of the year when low sun angles are experienced, for example by designing shading elements if needed.
All of these aspects come together to create buildings that are comfortable to be in all year round, no matter what the weather is doing outside!
There are many certified and non-certified components that can be used in a passivhaus building, from windows and doors to MVHR units. Both certified and non-certified products can be used to create a passivhaus building.
Under the Technical Standards a building's performance in terms of it's overall energy balance is calculated using the SAP methodology. A passivhaus design is always verified using the PHPP methodology, which is a complex set of inter-related spreadsheets designed by the PHI.
The process of designing a passivhaus through to the final certification process can seem daunting at first, however as long as it is considered from the onset of the project it can be a straightforward process. There is a considerable amount of information required and checks to be made by the designer at key stages: we aim to make this process as simple as possible for the client by presenting their choices in a clear and concise manner, at the appropriate time in the development of the design. If you would like more information about the process please contact us directly.
There are many misconceptions regarding what is and isn't possible in a passivhaus building: we have answered some of the most common ones we have been asked here. If you have any that aren't covered please feel free to get in touch.
Why it is all important?
There are many reasons why passivhaus is a useful and viable approach to low energy design, and designing for the future.
Financial: Rising energy prices are a concern of many types of people now, and no one likes to spend more money on something than they have to. The lowered running costs of a passivhaus construction are a considerable incentive for many.
Protection of the construction: There are many research papers that highlight the importance of managing moisture within a building and consequently preventing long term damage to the construction. Passivhaus can assist in this as the high level of airtightness demanded prevents the infiltration of unwanted air, and the consequential movement of moisture, into the building fabric where it can become trapped and lead to degradation of materials and the formation of mould.
Sustainability: Many people feel that if they can do their small part to
contribute towards a lower energy future then the world will benefit as a whole. Passivhaus is an energy standard first and foremost, however it is very compatible with other green agendas and ideas, such as breathing construction and natural (or minimally processed) materials and finishes.