Passivhaus Design Services

ECD Architects have been designing and building low energy buildings since completing the Futurehome project in Milton Keynes in 1981. Over the decades, the energy required to make our buildings comfortable has reduced significantly with better understanding of building physics coupled to improved construction components and systems.  With the introduction of the Code for Sustainable Homes, this trend is set to continue apace and at the cutting edge of this advance is the Passivhaus approach, recognised worldwide as the gold standard in energy efficient design. ECD Architects intend to embrace this design philosophy as they move into their fourth decade of practice and have underlined this by becoming Founder Members of the Passivhaus Trust, an independent, non-profit organisation that will provide leadership in the UK for the adoption of the Passivhaus standard and methodology.

Why Passivhaus? 

 Passivhaus buildings achieve an 80% reduction in space heating requirements, compared to standard practice for UK new build - with a continual rise in energy bills, that level of performance cannot be ignored. Chris Huhne, Secretary of state for Energy and Climate, has stated that the Passivhaus standard is "a watershed moment in our relationship with the built environment" and he "would like to see every new home in the UK reach the standard."

The Passivhaus standard therefore gives a robust method to help the industry achieve higher levels of the Code for Sustainable Homes and the overarching carbon reductions that are set as a legislative target for the UK Government. They are built with meticulous attention to detail, rigorous design and construction according to principles developed by the Passivhaus Institute in Germany, and can be certified through an exacting quality assurance process. Evidence and feedback from over many years of monitoring in Germany also shows that Passivhaus buildings are performing to standard, which is also 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%. Passivhaus standards will become ever more relevant next year when the Code for Sustainable Homes level 4 is expected to become a requirement for Government funding and for planning permissions in many areas. Code Level 4 will be required for any new homes built in London after April 2011.

Perhaps just as importantly however the Passivhaus standard focuses on achieving exceptional occupant comfort standards, both in terms of thermal and air quality benchmarks. It does this through greater attention to every aspect of the built fabric:

• building shape; to minimise the extent of exposed surfaces for the desired floor area and, therefore, heat loss through them;
• orientation, to maximise benefit from the sun’s ‘free’ heating;
• super-insulation, using thermal bridge-free construction to ensure that all internal surfaces remain warm whatever the external conditions;
• high performance windows, to eradicate downdraught effects;
• airtight construction; to remove risks to fabric degradation and further reduce heat losses; and
• heat recovery ventilation; to provide fresh, filtered, pre-warmed air to every room.

What is the Passivhaus standard?

To ensure that these conditions are met, the Passivhaus Planning Package (PHPP) software is used, which operates not only as a design tool but also a key component in the certification process. Each Passivhaus design is founded on its regional climate data resulting in a specification rooted in the local context and conditions. PHPP allows features of the design to be optimised to meet the key Passivhaus standard criteria:

• a maximum space heating and cooling demand of less than 15 kWh/m².year or a maximum heating and cooling load of 10W/m² (around 4-6 times lower than current UK standards)
• a maximum total primary energy demand of 120 kWh/m²/year (including lighting, appliances etc)
• an air change rate of no more than 0.6 air changes per hour @ 50 Pa (more than sixteen times better than Building Regulation requirements)

To meet these criteria in the UK it will typically mean:

• external envelope U-values of 0.15 W/m²K or less
• windows and doors with an installed U-value of less than 0.85 W/m²K, and
• heat recovery ventilation with an efficiency of 75% or greater (as certified by the Passivhaus Institute)

Because these criteria will have to be certified as having been met by an accredited body, for example the BRE or Warm Associates, the Passivhaus process operates as a quality assurance scheme, delivering maximum comfort for minimum energy – very much in line with the ECD philosophy.