In the context of a changing climate and increasing energy prices, we would all still like to live in a house, work in an office or attend a school that is comfortable and pleasant to inhabit. Passivhaus is a certified standard of build quality and performance, but ultimately is focused on how this benefits the occupants: consistent temperatures (warm and cool), no draughts, good air quality, no mould, and perhaps most importantly, low bills.

To achieve these outcomes, the basis of the Passivhaus strategy is a highly insulated and airtight building envelope, and a steady supply of fresh air via a mechanical ventilation system with heat recovery. Starting with these principles and using a specialist software called PHPP (which we will explore in another topic), a Passivhaus designer would then consider the ‘energy balance’: heat loss through the building fabric and through the ventilation versus the heating system plus the solar gain and internal gains. In the most efficient examples, one can warm a Passivhaus just by using the body-heat of the occupants!

The confusingly named EnerPHit is the name given to a Passivhaus-standard retrofit of an existing building. Accordingly, the criteria are less stringent than a new-build, but it would still out-perform most new construction. Ep architects are working on both domestic and non-domestic EnerPHit projects and are enjoying the challenge of developing how existing buildings can be repurposed and regenerated to positive purpose.

Considering the first Passivhaus in Germany celebrated its 33^rd birthday this year, you might ask why we’re so behind the curve. There are lots of myths that surround Passivhaus, such as it’s prohibitively expensive and the airtightness is stuffy and suffocating. Like any construction project, the earlier a strategy is adopted, the more cost-effective it becomes, so creating a Passivhaus from first principles can be as little as 5% more expensive than a ‘standard’ building. And contrary to popular belief, a Passivhaus can have opening windows, it just doesn’t rely on them for background ventilation, so no need to suffer cold draughts in the winter.

Of course, EnerPHit, depending on the condition of the existing building, can be a relatively expensive process and so you would need to consider the benefits of doing it, rather than just the financial payback, and whether a less stringent target such as AECB or LETI would be more appropriate. If you have a whole-life approach, then this undoubtably is something you should seriously consider as the reduction in energy use over lifetime and operational savings are a significant factor.

Our colleagues and team members here at ep architects: James and Rupert are qualified Passivhaus designers, so if you would like to talk more about the subject, feel free to drop in at our Romsey studios or get in touch.

Please do not be afraid to ask questions and discuss, whether you agree or disagree!

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