One stubborn trope in some corners of green building is that Passivhaus is so focused on energy performance that it advocates ignoring materials, Not so, argues Greengauge Director Toby Cambray.
Objections to Passivhhaus based on environmental impacts are nonsense, but they also hint at more systemic problems with the industry, which have been exposed by the Grenfell enquiry. A key observation of the enquiry is the complexity of the failure, including aspects from the technical, commercial, regulatory and cultural realms. In this piece I’m reflecting on just one element of this multi-faceted tragedy.
We often hear complaints from those sceptical of Passivhaus that it fails to address up-front carbon and other issues that aren’t directly associated with operation energy. To anyone who understands the slightest thing about Passivhaus, this is an anathema. The implication is that Passivhaus encourages us to use lots of concrete, plastic foam insulation, and other things that are, or are at least perceived to be, bad with respect to environmental issues other than operational energy. This is not the case, and I’ve yet to meet a Passivhaus proponent who doesn’t also care about all of these other impacts.
A lot of the hang ups seem to be around insulation, because you often need a bit more than in a regulation standard building – but even this ceases to be true for very low form-factor buildings such as, say, a tower block of flats. Furthermore, insulation is not very dense, so the impact per unit volume is small.
We all know that there’s only one number you need to know about insulation: the conductivity. With that, you can decide what thickness of material is required to achieve a U-value, and then you can go to the pub.
This is of course nonsense, because there are many other factors that are necessary for insulation to do its job. Perhaps even more important, the insulation must perform as part of a system that is not just well insulated, but stands up, is airtight, is resistant to fire, low moisture risk, quiet, incorporates services, is maintainable, low in up-front carbon and other environmental impacts.
Arguably, this conductivity trap played a part in the Grenfell tragedy; the thinner build up that a lower theoretical conductivity allows has advantages that are compelling on a superficial level, but a proper decision must be based on a much deeper analysis which it seems was lacking from the Grenfell design, and countless other schemes.
For Passivhaus, it’s not just about U-values; the form, fenestration/orientation, infiltration and ventilation influence how good the U-values need to be.
Get these things right and you need less stuff; not just insulation and super high performance windows, but less structure and finishing material. Passivhaus incentivises fabric sufficiency through the medium of operational energy.
These critics seem to often be the materials fetishists, who make the latest hand knitted seagrass – or literally anything, as long as no-one else has used it yet – the focal point of their designs. This is approach simultaneously at odds with, and symptomatic of, the shortcomings that Oliver Wainwright bemoans in the Guardian in September this year: “architectural education is a five-year training in visual representation and rhetorical obfuscation, with precious little time spent on learning how to actually make a building.” There are notable exceptions to this and some schools of architecture do furnish their students with a sound technical base, but my sense is that , for many universities, Wainwright is on the money.
The thing is that buildings are complicated; they need to do a lot of things, some of which are easy to count while others are intangible; many are essential, and some are purely whimsical. It is really hard to balance off all these things, but to do so successfully we must engage seriously with all of the constraints simultaneously – including beauty.
The wilful misunderstanding of Passivhaus and the incompetence demonstrated in the design of the Grenfell cladding, both belie a reluctance to address the manifold challenges that designing in the 21st century involves. Picking the insulation should be the easy bit. Its harder to integrate it into a scheme that’s successful on all the other criteria. And even that pales in comparison with making a culture, an economy and a society where everyone is safe and happy while operating within planetary boundaries. But it is this which we must try to do.
Originally published in Passive House Plus magazine
