What is Passive House?
Passive House or Passivhaus, has been around since the 1980s. It was the idea of Professors Wolfgang Feist and Bo Adamson following the 1970s fuel crisis, building the first Passive House in Darmstadt, Germany. The Passivhaus Trust, the UK’s affiliate of the Passivhaus Institute, was founded in 2010. So, whilst the Passive House concept is relatively new to the UK it is a globally recognised standard of building.
Passive House standard reduces the energy used to heat and cool a building to the minimal amount practical. This equates to 15kWh/(m2.yr) or around 70% of the energy a new building property would use. This ensures that the additional costs of insulation and ventilation are paid back through savings in lower energy usage. For example, a Passive House retrofit and extension we have recently calculated would save £165 a year compared to if the 2023 government minimum standards were applied.
Many people believe that the Passive House standard is all about energy reduction. This is only partly true.
The definition of a Passive House, as described by Passipedia, “is a building, for which thermal comfort can be achieved solely by post-heating or post-cooling of the fresh air mass, which is required to achieve sufficient indoor air quality conditions – without the need for additional recirculation of air.”
In this definition of a Passive House building, there is little mention of energy. The focus is on thermal comfort and indoor air quality. This is backed up by the detailed criteria of Passive House design. There are 2 “hard” criteria - defined in the certification - and around 12 “soft” criteria for comfort. Meanwhile, there are only two obligatory energy-specific criteria to satisfy. Some, including Ayshford Sansome, argue that Passive House is therefore a standard of comfort first and foremost.
It is only when we define a Passive House in numerical terms that the energy becomes the focus. This is because once the energy requirements are achieved most, if not all, of the comfort criteria are also achieved.
Furthermore, a Passive House is not just a standard for homes. There are examples of car dealerships, leisure centres, churches, offices, and superstores that are all Passive House certified. In fact, there are examples of existing buildings being retrofitted to meet the Passive House standard. For examples of the variety of styles and types of Passive House buildings completed globally to date, check out the Passive House Database. https://passivehouse-database.org/index.php?lang=en
Because a Passive House building is designed and built around 5 key principles: super insulation, passive house windows, airtightness, heat recovery ventilation (MVHR) and ‘thermal bridge’ free construction, the Passive House standard is applicable to all buildings. In fact, the German term ‘Haus’ can be translated as both house and building.
Finally, there is a misconception that a Passive House design results in a plain or uninspiring-looking building. Whilst the Passive House principles are based in science this should not restrict design flexibility, and the result will depend on the architectural skill of your designer. One might consider the variety of dog breeds that exist. They follow the simple rules of having a tail, four legs and fur, but the variety of dog breeds is countless and beautiful – unless you don’t like dogs of course!
If you would like to know more about Passive House buildings, or like the idea of very low energy bills in your next project, Ayshford Sansome offers certified Passive House designer services and would love to hear from you!
Or read our blog post on the benefits of Passive House here.