PassivHaus? What’s that?

As individuals we are all becoming increasingly aware of climate change issues and the need to live sustainably. As an Architect, I recognise that I have extra responsibility for our future and that of our children. Any building I design now, is probably going to be in use for 100 years or more, consuming energy at ever increasing cost. Car designers have long been seeking to meet demand for reduced fuel consumption by designing high-tech cars so why not Architects?

The millennium saw the peak in world oil production and a significant decline in production is expected over the next century. As oil (and natural gas) prices rise, hikes in the cost of energy bite into our stretched budgets, both at home and in business. For Landlords, this also places rental income at greater risk. As individuals we are all becoming increasingly aware of climate change issues and the need to live sustainably.

As an Architect, I recognise that I have extra responsibility for our future and that of our children. Any building I design now, is probably going to be in use for 100 years or more, consuming energy at ever increasing cost. Car designers have long been seeking to meet demand for reduced fuel consumption by designing high-tech cars so why not Architects?

Whilst appearing to provide a simple resolution of the Carbon problem, renewable energy ‘bling’ is not all it first seems. Photovoltaics (PVs) remain expensive to install and may only last around 25 years. Even with the Government’s Feed-in Tariff break even is around 20 years on investment. Solar hot water shows a better pay-back period, but why spend money on its installation when we have buildings that throw away heat in the first place? Wind power requires an average wind speed of 4 metres per second and that is not as common as we would hope. So, how can this conundrum be resolved? It is for this reason that I became attracted to PassivHaus.

In Austria and Germany, they have long been designing buildings to the principles of PassivHaus. Public awareness, aided by coverage on Grand Designs, is rapidly growing in the UK. Developed by Professor Wolfgang Feist from Innsbruck University, and now enshrined in the German PassivHaus Institute’s Standards, it cleverly ties design and construction together to achieve very low heat demand buildings.

Why Passiv? It takes its name from using ‘passive’ design techniques. The classic example of this would be the comparison between a coffee percolator using electricity to keep the pot warm and a flask, which uses no energy.

A new building built to PassivHaus will achieve accreditation only if its design predicts that the building will use just 15kWh (or less) per m² to heat it in a year. A 3 bedroom house of (say) 60 m² would only require 900kWh in a year. Even at a cost of gas of 6p per kWh the annual heating bill would be £54. However, a significant advantage of Passivhaus is that there is no need for central heating at all. For example, in a PassivHaus a room of 20 square metres can be heated by 10 tea-lights or the heat given off by 4 humans!

So how does PassivHaus work its magic? There are 4 basic principles:

  • Minimise heat loss by high insulation levels 
  • Maximising solar heat gain in winter months 
  • Minimise heat lost through thermal bridging 
  • Minimise heat lost through ventilation by using heat recovery

What about renovation work? PassivHaus recognises there are issues. Retro fitting of significant insulation is not so easy, installation of mechanical ventilation systems may be difficult and building orientation and form is already determined. In recognition of these difficulties, the PassivHaus Institute has an alternative accreditation scheme called EnerPHit. This permits design to a raised level of 26kWh per m².

PassivHaus works. It works by default for the life of the building. It is not dependent on significant energy use and so protects the building owner from an uncertain energy future. It ‘feels’ warmer due to lack of low surface temperature materials. It feels comfortable, with cleaner, purer air and thanks to the removal of the need for central heating systems it does not necessarily lead to higher building costs.

Constructing a PassivHaus will require dogged determination in design and also close collaborative work between your Architect and a committed builder. Finding an Architect who is versed in PassivHaus may prove difficult. As a first port of call, The PassivHaus Trust website (www.passivhaustrust.org.uk) can provide details. Alternatively, contact the writer!

**With thanks to Jeff Hitchcock, Partner, Burns Guthrie and Partners.

For more information please see: http://www.burns-guthrie.co.uk/ or by contact through [email protected]**