So as I may have mentioned, I’m a Certified Passivhaus Designer, one of only a handful in Hertfordshire, but this doesn’t mean a lot to most people. In this post I’m going to try and explain a little bit about the Passivhaus standard and what its benefits are.
According to the Passivhaus Trust: ‘Passivhaus buildings provide a high level of occupant comfort while using very little energy for heating and cooling. They are built with meticulous attention to detail and rigorous design and construction according to principles developed by the Passivhaus Institute in Germany, and can be certified through an exacting quality assurance process’.
The basic principle of a Passivhaus is to reduce the heat losses of a building to the point that it hardly needs any heating at all. The sun, occupants, household applicants and the warmth from extracted air cover most of the heating demand. The standard relies on good levels of insulation with minimal thermal bridges and well-designed uses of solar and internal gains. The buildings are made as airtight as possible which results in the installation of mechanical ventilation heat recovery(MVHR) systems which provide excellent air quality and heat recovery efficiencies in excess of 80%. All of this means that a traditional heating system is no longer required and the shortfall can be covered with a small unit, such as a wood burning stove. There have now been documented cases of Passivhaus buildings having zero heating bills – how awesome is that!
Despite what you may have heard, you can open windows in a Passivhaus – in fact, they are often open more than in ‘conventional’ houses because they stay so much warmer! And they do not have to be box-shaped, just have a quick Google! A quick shout out must go to a former tutor and critic of mine, Graham Bizley, how has built a beautiful Passivhaus for his family in Somerset, give it a look here. Clearly, its not just a box!
And despite the name, its not just houses that can be Passivhaus certified, there are a growing number of non-domestic Passivhaus buildings in the UK, particularly schools.
If you want to know more, Elrond Burrell writes a brilliant blog about Passivhaus where he addresses the basics as well as listing links to a variety of resources for further information about Passivhaus and the certification process.
Passivhaus certification is also possible for very low energy retrofit projects. EnerPHit is a slightly relaxed standard for retrofit projects, where the existing architecture and conservation issues mean that meeting the Passivhaus standard is not feasible.
To achieve the Passivhaus Standard in the UK typically involves:
Passivhaus buildings achieve a 75% reduction in space heating requirements, compared to standard practice for UK new build. The Passivhaus standard therefore gives a robust method to help the industry achieve the 80% carbon reductions that are set as a legislative target for the UK Government. Passivhaus also applies to retrofit projects, achieving similar savings in space heating requirements.
Evidence and feedback to date shows that Passivhaus buildings are performing to standard, which is crucial, given that the discrepancy between design aspiration and as-built performance for many new buildings in the UK can be as much as 50-100%.
But there are reasons to build a Passivhaus that go beyond simply energy efficiency:
Passipedia has a fantastic series of webpages on the Basics of Passivhaus and the Passivhaus Trust has published a series of guides for people considering the Passivhaus standards, both of which can offer more in depth information, or alternatively drop me a line!