I've been asked a handful of times lately - 'So... what do you think about Passivhaus?' and I reckon it's a good excuse to get back on the old blog writing and summarise my most recent thoughts. I hope you enjoying reading, and please do get involved by commenting and sharing.
Previous to the last six months I've been a bit of an 'eco purist' about the whole Passivhaus concept, focusing only on it's flaws and unwilling to compromise and let the pros shine through. In a nut shell, for those less familiar, Passivhaus is the quality assurance and energy performance standard - 'the worlds leading fabric first approach to low energy buildings' which originates from Germany and focuses on a buildings fabric as a way to lower energy usage.
Passivhaus places importance on high levels of insulation and an airtight external envelope, with the assistance of mechanical ventilation and heat recovery systems. They seek to remove thermal bridges from the construction, use high performance windows and doors with insulated frames, and to reduce the heating demand and dependance of fossil fuels.
I'll start with the issues I have with Passivhaus:
High Levels of Insulation - there are no restrictions to the type of insulation you can use or limitations to the distance in which it requires to travel. Passivhaus certification can be achieved with fossil fuel derived expanded phenolic foam (kingspan, celotex etc) and shipped from across the globe. Buildings could be made with far more natural breathable materials and sourced as locally as possible, reducing carbon emissions in the construction process and increasing the overall air quality of the finished building.
Air Tightness - By making the buildings airtight, ventilation is required, passively or mechanically to ensure there is adequate airflow and no build up of condensation which leads to mildew, damp and mould. If a Passivhaus were to be left standing with no mechanical ventilation running and no inhabitants for a period of time, it would result in a stuffy, unhealthy internal environment and potential moisture problems. Buildings could be designed and made with breathable heat retaining materials for thermal mass, and for passive ventilation to keep the spaces fresh and still warm allowing the building to work even when not inhabited or 'plugged in'.
High Performance Windows & Doors - This probably covers thermal bridge free construction as well. I don't have an issue with these principles, but again it's down to the materials used and freedom to specify fossil fuel derived products made in the arse end of nowhere and shipped across the world. Buildings could be made from natural and low embodied energy materials resourced as locally as possible. Low energy buildings, that are high energy in construction are sort of counter productive in the overall energy demands of the planet, are they not?
Mechanical Ventilation & Heat Recovery - Ooo this one I had such a beef with for a long long long time. This is my most recent to get over and possibly the main point that's tipped me back to balancing point. Why design an energy efficient house that RELIES on energy to function correctly. The entire philosophy is to reduce energy usage, and the backbone of this entire concept relies on the one thing it tries to reduce. It's an oxymoronic system. There, that's all I'm going to say.
I've not engaged in arguments - sorry 'discussions' - about Passivhaus since Part II at C.A.T where I found it very difficult to explain to logical, Passivhaus minded students, lecturers and sustainable M&E engineers why I felt so strongly against it. It seemed nigh on impossible to explain my thoughts despite many scribbles and rants, and trying to figure it out in my own head. There always seemed a promoter just poised ready to fight against my 'purist' ideals. It seemed like it was logic versus gut instinct. I was on the side of gut instinct, and you can't academically argue gut instinct. There are no examples and fluffy feely airy fairy answer to - it just feels better to be in a passively designed, naturally made, breathable warm house.
Six months ago I realised my perspective had changed somewhat. While I've been working and living in West of Scotland, and being part of the Scottish Ecological Design Association hosting events and talking to individuals, designers, studios and governing bodies, it's extremely obvious to me that there is a growing mass of normal, every day, members of the community that are interested in and are growing their awareness of wider sustainability issues, and the effect of the built environment.
Students are arriving at university with these ecological values; awareness is spreading of harmful toxins and plastics and cancers and genetically modified food; parents are concerned over the effect of technology on their children and what they feed them; hospitals and schools, affordable housing - they want better for their inhabitants; energy consumption reduced, renewable technologies invested in, local support of crafts and skills...these things are all on the rise and so I realise that it doesn't do much harm to have a minimum standard - a household name - an identifiable, explainable set of criteria on which to start increasing the standard of the built environment.
As Kirsty Maguire puts it, it's 'Passivhaus by stealth.' If you can convince people that what they want and need is healthy, comfortable, enjoyable buildings, with reduced bills and at a decent price, then there's the starting point. I can't tear Passivhaus down for not being as green, or natural, or sustainable, as it could be, as much as I could be praising it for increasing the minimum standards that we already adhere to. If Building Standards adopted Passivhaus then it would significantly increase the quality of the built environment and drastically reduce the energy consumption of the country as a whole.
The most recent and relevant scenario to convince me of Passivhaus MVHR systems, was the weather we've been experiencing this winter. In temperatures below zero, with howling wind, to live in a house that is not airtight, where you can't open the windows because the bitter cold wind will cool the whole house, and the windows and doors are not high performing - Passivhaus makes a lot of sense. There, I said it. I 100% understand why mechanical ventilation while recovering the heat is a genius idea. I've been either freezing or oxygen deprived with my 'natural ventilation' system.
It's taken me quite a while to balance out, but I think there's a place for both Passivhaus promotion while still pursuing greener, healthier, simpler, 'purer' buildings. I can still strive to make things as excellent as they can be, while appreciating the effort of the real world applicable increase in standards that Passivhaus has to offer.