WHAT IS PASSIVHAUS?
The term ‘Passivhaus’ refers to a low-energy construction standard developed in the 1990s by Dr Wolfgang Feist of the Passivhaus Institut in Germany. It is the fastest growing energy performance standard in the world with over 30,000 buildings having been constructed in accordance with Passivhaus principles.
The core focus of the Passivhaus Standard is to dramatically reduce the requirement for space heating and cooling, whilst also creating excellent indoor comfort levels. This is primarily achieved by adopting a "fabric first" approach to design, with high performing insulation complimented by exceptional levels of airtightness and the use of heat recovery mechanical ventilation.
HOW DOES IT WORK?
The Passivhaus approach works by emphasising and quantifying a number of key design principles:
1. Insulation - the building is super insulated to minimise heat loss through the fabric, allowing only a 0.15w/m2k U-value.
2. Airtightness - by employing exceptionally high levels of airtightness, far in excess of current building regulations requirements, we can avoid heat leaking out of the building.
3. Thermal Bridge-free - having employed insulation and airtightness, we must now ensure that there are no weak points in the external envelope of the building, allowing heat to bypass the insulation layer.
4. Solar Gains - once we have established an efficient building shell, it is possible to use solar gains, with only supplementary heating systems, to heat the building all year round.
5. Heat Recovery - now that we have the solar heat, we must keep it. Heat recovery systems allow us to continually provide fresh
WHAT ARE THE BENEFITS?
The most obvious benefit to Passivhaus is that it improves energy efficiency.
In a Passivhaus, the heating requirement is reduced to the point where a traditional heating system is no longer considered necessary, and cooling is also minimised through the use of shading and, in some cases, via the pre-cooling of the supply air. This is obviously beneficial for our energy bills, and helps ease the transition to a sustainable energy future. But there are many other benefits to building in this way.
Passivhaus is a technical design standard, not a subjective aesthetic one. An important part of the Passivhaus ethos is that it doesn't necessitate any one design style; a Passivhaus can equally be a subtle vernacular design or an avant-garde contemporary statement, as long as it works.
The stable internal temperatures mean there are no noticeable draughts or cold surfaces.
The overheating requirement minimises the number of exceptionally hot days in the summer.
4. Air Quality:
The constant background ventilation means that, unlike traditional buildings, there is no build up of carbon dioxide, particularly at night. The ventilation system is also filtered, which removes a huge percentage of the particulate pollution in urban centres.
The stable internal temperatures also make it very difficult for mould to take hold.
The thick and airtight envelope of the house means that very little external noise can enter the building. This is particularly desirable near major roads, rail lines or airports. There are also strict controls on the amount of noise that can be created by the internal ventilation system itself.
6. Build Quality:
The elevated design standards and rigorous certification process make the risk of poor quality construction far less likely.
7. Stripped Back
Unlike some other design standards, the focus of Passivhaus is on performance, not image. This means that any money spent achieving the standard will result in a better building, rather than on a series of bolt-on additions.
WHERE CAN I FIND OUT MORE?
The Passivhaus Institut in Germany is the founding institution of the standard, and regulates its certification today.
In the UK, the Passivhaus Trust aims to promote the principles of Passivhaus as a highly effective way of reducing energy use and carbon emissions from buildings in the UK, as well as providing high standards of comfort and building health.
You can read more at the http://www.passivhaustrust.org.uk.
You can also find useful introductory guides to the Passivhaus standard at the following links: