ukpassivhausconference2014Our John Hyland is presenting at the UK Passivhaus Conference 2014 on 16 October and he'll be talking about the challenges faced from a contractor's point of view in achieving Passivhaus Standard on a retrofit project

It goes without saying that it is harder to achieve the required standards in a retrofit property than a newbuild, so the EnerPHit Standard was developed as the Passivhaus Standard for retrofits. The four requirements to achieve the Standard relate to:

•   Annual space heating requirement
•   Upper limit for total primary energy demand
•   The frequency of excessive internal temperature
•   Air leakage.  This will have a huge impact on the other three!

There are very many issues that an inexperienced contractor may come across when carrying out this type of work.

These projects can be difficult. The structures may be old and contain many voids that cannot be seen and are difficult to find.  Much of the work may have to be carried out 'blind' - drilling holes, pumping specialist foam into spaces you cannot see.  It involves lots of experimentation and multiple pressurised and de-pressurised air testing.

In a large block with multiple units, even if the units are all of the same house type and layout, you may find that each one is different to the last in terms of airtightness.  Measures that work in the first nine properties may be completely ineffective in the tenth, requiring new measures to be developed. Our experience has shown us that you need to take some very innovative approaches.  As this is a relatively new field, we have developed some new, ground breaking techniques.

One more thing, it is much more difficult to carry out 'normal' works in airtight properties. For example, the usual drying time of wet trades can be multiplied almost exponentially when carried out in properties that are effectively airtight, and within which the mechanical ventilation and heating have not yet been commissioned.

The notes from John's presentation are now available.  Click here.