What is the Passivhaus Standard?
As the leading international low-energy performance standard, attaining Passivhaus status is one of the most challenging but rewarding approaches to minimising a building’s energy usage.
In this weekly series of blog posts, building up to the Passivhaus Trust Conference in October, we will try and provide an introduction to what the Passivhaus standard is, the benefits and the requirements for achieving it as well as a brief look at the history of it.
The definition of a Passivhaus is:
A Passivhaus 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.
Basically this means a building that does not have a heating or cooling system like radiators and a central boiler. Instead, by reducing levels of heat loss through high levels of insulation and preventing air loss, the building is heated passively through the sun, human occupants and household appliances with the remaining heat being supplied through heating or cooling of air in a mechanical ventilation system.
It is a low energy construction standard that results in an energy efficient, comfortable, affordable and ecologically sustainable building. The standard requires a ‘fabric first’ approach to construction which means that the building does the work in achieving the thermal performance rather than relying on energy sources such as ground source heat pumps. It requires an exacting certification process throughout the design and build stages to ensure that what is designed is built, and what is built performs as it was designed.
The Passivhaus standard strengths lie in the simplicity of its approach; build a house that has an excellent thermal performance, exceptional airtightness with mechanical ventilation! This approach to building can be used for both domestic and commercial buildings and applied to new builds as well as retrofits.
The basic principles are to construct a building that has:
- good levels of insulation with minimal thermal bridges
- passive solar gains and internal heat sources
- excellent level of airtightness
- good indoor air quality, provided by a whole house mechanical ventilation system with highly efficient heat recovery.
Passivhaus is sometimes compared to or confused with the Code for Sustainable Homes and BREEAM ratings for non-domestic buildings. In reality the distinction is quite simple: Passivhaus is a specific energy performance standard that delivers very high levels of energy efficiency, whilst the Code and BREEAM are overarching sustainability assessment ratings which address a large number of environmental issues.
One of the key factors for a Passivhaus is that it is well insulated to a level much higher than that required by today’s building regulations. The thermal insulation requirements of Passivhaus demand that roof, wall and floor U–values are equal to or less than 0.15 W/m2.K. To achieve this high performance insulation is required so that the space taken to achieve the stringent U–value is kept to a minimum.
To promote the principles of Passivhaus as a highly effective way of reducing energy use and carbon emissions from buildings in the UK, Kingspan Insulation became one of the founding members of the Passivhaus Trust.
The top image shows houses built to Passivhaus principles for the Highland Housing Expo 2010. To see some more examples of the Passivhaus Standard in action download our Passivhaus Projects brochure, and explore the case studies.
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