Good System, Bad Law

A number of articles I’ve written have referred to Passivhaus (or Passive House, to use the English translation), a voluntary international standard for low-energy houses. Roughly speaking, Passivhaus keeps heating and electrical bills extremely low by superinsulating the building fabric, using high levels of draughtsealing, and using mechanical ventilation to keep fresh air coming in while preventing heat from flowing out. This is the standard that Dún Laoghaire-Rathdown voted to make compulsory on all new buildings as a condition of planning permission.

Dublin City Council’s representatives recently followed this lead and voted to make Passivhaus compulsory in a similar way. For obvious reasons this is a very wide-reaching decision, as Dublin City Council can expect to see by far the most planning applications in any given year. However, on this occasion the decision didn’t stick. The Council’s officials effectively refused to put this in the development plan, on the basis that it is a Building Regulation rather than a planning matter.

Whether the officials are right in this regard is open to question. Mandating a building standard through Planning Permission is certainly not in the spirit of how Ireland’s construction regulations are set up, but whether it’s actually ultra vires isn’t clear one way or another; on the one hand Dún Laoghaire-Rathdown received legal advice that it was permissible but, on the other, Planning Permission is supposed to be about ensuring “proper planning for the area” and it’s hard to see how insisting on a particular construction method falls within that remit. If you are in favour of mandating Passivhaus, the overruling of the councillors seems like a worryingly anti-democratic development; if you are against the measure, it’s probably a question of sanity prevailing.

(It can also be both of those things, of course.)

I don’t believe making Passivhaus mandatory is a good idea. I’ve already written about one reason, which is that is in effect a proprietary system¹. This piece has a different focus: while Passivhaus is a good system for building low-energy houses (I genuinely hope to have the opportunity to design one in the future), it is a very bad basis for regulation. It was created and envisaged as an opt-in system, one with which individuals could choose to comply, and is fundamentally unsuited to being a compulsory, nationwide (or even county-wide) building standard. Regulations and voluntary standards do different things, and need to approach the same issues differently. Voluntary standards can be prescriptive; regulations need to be inclusive. Voluntary standards focus on the individual user’s benefit; regulations focus on the benefit of everyone. As a voluntary standard Passivhaus is excellent, but a voluntary standard is how it should remain.

That’s a fairly general point, so to make it more specific I’m going to turn things around. Let’s look at what’s commonly said to be a reason that Passivhaus should be made legal, and parse the arguments in its favour. What emerges is a picture of a standard that’s too personal and too restrictive to function as law, and doesn’t bring anywhere near enough positive gain to compensate for its limitation.

  • Passivhaus is an innovative system, not a brand

This general point is maybe the best place to start. I’ve seen people describe the idea of mandating Passivhaus as “promoting innovation” rather than restricting competition. Lurking at the bottom of this idea is the notion that, because a Passivhaus can be built using all sorts of different constructions, and because it’s monitored by a non-profit institute in Germany, it’s not a “brand” as such.

This is a fallacy. The best way to understand Passivhaus is that it’s an open-source system. If you’re one of the statistically high number of people reading this blog on Firefox, you have a perfect analogue. Firefox makes its source code freely available for others to view, modify and redistribute, just like Passivhaus systems can be adapted by the user; it’s created and maintained by Mozilla, a non-profit organisation. But nobody would claim that Firefox isn’t, clearly, a proprietary brand.

Skip back ten years, and Firefox was comfortably the best of all the widely-available browsers. It was faster than Explorer and Safari, more functional than Chrome, and came with lots of extras (like tabbed browsing) that its competitors hadn’t created. But it would have been absurd to pass a law stating that all browsers had to be Firefox (or “robustly tested” to prove they were as good as Firefox). As for claiming this was promoting innovation, it would be self-evidently ludicrous.

The Passivhaus standards – a highly insulated thermal envelope, extremely high airtightness in the fabric, triple-glazing or similar at windows, and mechanical ventilation with heat recovery (MVHR) – are not the only way of building a low-energy house. Even if you believe that Passivhaus is currently the best system (and let’s face it, believing in a one-size-fits-all “best” solution is a mug’s game), there’s certainly no reason to assume this will always be the case. If you want to stick a few solar panels on your roof and lower the insulation standards, there’s no good reason that the state should stop you. If you want to naturally ventilate your house, there’s no good reason to stop you doing that, either. Insisting on Passivhaus as the only acceptable solution is the opposite of promoting innovation.

  • It massively improves the energy-efficiency of new houses

It simply doesn’t, and this is perhaps the most widely-held misconception. Passivhaus represents, at best, a fairly small improvement on thermal performance over the Building Regulations as they currently stand. In 5 years time Ireland is due to switch to Nearly Zero Carbon as a standard, at which point Passivhaus will not be an improvement at all.

The worrying thing here is that many of the councillors who voted for Passivhaus don’t appear to understand what they voted for. The brand marketing, including the completely inaccurate name “Passive House” (Passivhaus isn’t passive by any meaningful definition of the word) and the false rhetoric of “homes without a heating system” (the Passivhaus Institut once claimed on its website that the houses heated and cooled themselves, which remains a widely-circulated falsehood: the claim that these houses don’t need a conventional heating system is discredited, but still frequently reported as fact), has even convinced some politicians that they are zero-carbon houses. None of this is true. Passivhaus is based on sound insulation principles, but it isn’t a significant improvement on the thermal performance required by current regulations.

The fact is that regs-compliant houses will need a BER in the region of a mid-level A3 to pass; apartments will have to perform better still. If houses are already performing so well, there just isn’t that much more energy to save. As it happens, most Passivhauses will be somewhere in the A2/A3 range, although a few perform as low as B1. It’s generally thought that a medium-sized Passivhaus costs €50-60 to heat per year. Even if you accept that their heating bills are – say – one-third that of a new house, which is highly optimistic, that’s a saving of €100 per annum, if at all. If you only pay €2000 extra to “upgrade” to Passivhaus, it will take 20 years to make that money back (before you factor in interest payments, of course). So Passivhaus is not a significant improvement when it comes to energy use, and any claims to the contrary lack proportion.

  • It’s about fighting climate change

To claim Passivhaus is needed as a standard because of climate change is simply absurd. The most obvious objection to this is one tackled above: compared to a typical Part L house, Passivhaus’s energy use is not a great deal lower. If you really want to do something about climate change, then insisting low-energy houses become slightly-lower-energy houses is a daft place to focus your resources. There are hundreds of thousands of houses in Ireland which have very little insulation or none at all, and these houses account for the overwhelming majority of the energy we use to heat our homes. Why not focus resources on retrofitting these with insulation, rather than wasting time, money and energy saving fractional amounts of energy on new houses?

This image (click for the original, excellent article) demonstrates that Passivhaus is a poor way of reducing collective energy use. The extra insulation required by a Passivhaus standard would be more effective split between several uninsulated houses.

The other important thing to understand about Passivhaus is that it’s primarily a personal comfort standard; it’s about giving the individual a low-energy home that’s comfortable, not about regulating energy use in society. It has, for example, a “small house premium” – it’s easier for larger dwellings to comply than small ones. For an opt-in personal standard, that’s fine: your only concern is whether the internal climate is to your liking. However, if we’re talking about a society’s energy use, it’s obviously perverse to penalise smaller dwellings.

Additionally, many of the requirements are nothing to do with saving energy. For example, one of the requirements of Passivhaus is the use of triple-glazing². This saves hardly any energy – triple-glazing doesn’t perform that much better than double-glazing, and when you consider the energy being used to make 50% more glass it becomes even more dubious. The triple-glazing standard is there to prevent “cold spots” near the window, which reduces air currents and makes the environment more comfortable. That’s nice, but we’re clearly into a luxury bracket of internal comfort here; it is not the sort of thing that should be written into law. Turning low-energy buildings into slightly-lower-energy buildings is simply fetishisation of comfort standards, it’s nothing to do with climate change and to claim otherwise is delusional.

  • They are better-built

It’s certainly true that, if you take a typical Passivhaus, it will be better-built than a typical house built in the country today. Of course it is: it requires excellent construction standards to work, and all parties have made a conscious decision to achieve this. The client has done the research before deciding to build one; the architect will usually be a specialist in the area; the builder will probably be certified, and at the very least will be taking it seriously. You won’t be getting a lash-it-up-and-forget-it merchant trying to do it on the cheap. In short, they are being commissioned, designed and built by a self-selecting group who are already interested in this sort of thing.

However, those who advocate switching to Passiv appear to think that there’s something about the system itself that makes people build better. This is a false premise. The Irish Olympic team is made up of the fittest people in the country, but that doesn’t mean you’ll instantly get fitter if you’re put on the Irish Olympic team. At the moment, the number of Passivhauses built in Ireland is less than twenty per year. They’re built by a limited pool of highly-trained, highly-motivated people. Once you step that number up from “dozens” to “tens of thousands,” you have an entirely different group of builders getting involved. We know, from experience, that the majority of these builders aren’t even building Part L houses properly.

The only data is from this study which suggests, shockingly, that practically no new houses in the country are being built fully in accordance with the regulations. Ask those builders to build a Passivhaus, and all you’ve got is a massive skills gap. This is what needs to be tackled, urgently. If we can’t expect new houses to be designed and built in accordance with TGD L, what on earth makes us think that they can be built to an even more complicated and demanding standard?³ It’s like a teacher, if faced with a maths class that can’t do long division, “fixing” the problem by starting them off on advanced calculus.

  • There is no performance gap with Passivhaus

One of the issues cited by Passivhaus advocates is that, while Passivhauses perform more or less as the computer models predict they will, typical houses built to Part L don’t tend to perform as well as the theory says they should. The shorthand for this is the “performance gap.”

A large part of this conversation links in with the issue of construction, as discussed above; houses don’t perform as well as expected because they aren’t being built properly, and mandating Passivhaus will not spontaneously improve construction standards in the country. However, some argue that the performance gap is also due to the systems – effectively, that DEAP is a crude tool compared to the Passivhaus software (PHPP), and as a result doesn’t properly assess how much energy a house really uses.

This is a deepy flawed argument, as DEAP is trying to work with a broader range of construction, so it isn’t directly comparable to PHPP at all. The rough theory behind Passivhaus is that the internal temperature is maintained at twenty degrees centigrade, twenty-four hours a day. For obvious reasons this is straightforward to assess. DEAP is different: it assumes that most houses will only be heated for a portion of the day, as for long stretches of time the house may be unoccupied (i.e. when people are in work) or unheated (the middle of the night). Fair enough, but it means that all DEAP – or any other software – can do is guess what a typical occupancy might be. It’s not intended to give a 100% accurate heating figure, it gives a notional figure that enables one building to be compared to another. Many of the people who complain about DEAP’s inaccuracy are just expecting it to do something that no piece of software can do.

The fact is that it’s pretty perverse to insulate, draft-seal, and mechanically ventilate a house (with all the extra money that requires, not to mention the embodied energy that goes into producing all those sealants and insulation) to such a level that it maintains a temperature of 20°C even when there’s nobody in it – especially in a climate as temperate as Ireland’s. Even if the house is constantly inhabited, there’s no need to keep some rooms so warm (toilets, utility rooms, and even bedrooms are perfectly fine at 18°C).  A system that relies on the house being kept at 20C has just replaced a “performance gap” with another, bigger problem: namely, whether keeping a house at this temperature is necessary at all.

The claim that “but there’s no performance gap with Passivhaus” is the perfect example of circular logic. There’s software that accurately assesses how much energy a Passivhaus uses, but it can’t assess other housing types with the same accuracy, therefore every house should be Passivhaus so the software can get the numbers right. But making decisions based on software accuracy is far from solid reasoning.

  • Passivhaus is Cheaper

This claim is often-repeated, even though I have yet to read a single case study which shows that it is even vaguely true, and everything we know suggests that it is nonsense. It’s possible to argue it’s not much more expensive; it’s possible to argue that it’s good value. But cheaper? No.

This piece on Passive House + magazine (to which I’ve referred previously) is a good example of how the “Passivhaus is cheaper” argument tends to be conducted. In the article, every construction step is compared to a “Part L house” and the Passivhaus alternative is shown to cost the same or less. But this is bogus; there’s no such thing as a “Part L house”. The “Department’s suggested values” to which the piece refers are not rules or recommendations, they’re sample figures and nothing more. You might as well say the answer to every quadratic equation is six, because the example in your maths book which gives the answer six. The real conclusion of the piece is “you can build a Passivhaus as cheaply as a standard new-build house that’s designed and built in a way that isn’t cost-effective, if you spend a long time looking for cheaper solutions.” Well, sure. But that’s obviously true of any new house.

The simple fact is this. Compared to a standard new build house, Passivhaus will need more insulation, triple glazing, and a mechanical ventilation system with heat recovery in order to function. There will also need to be much more management in order to achieve the high levels of draught sealing that Passivhaus requires. To say you can build this “cheaper” is bizarre.

The one thing that might make sense of the “Passivhaus is cheaper” argument is the point that Part L stipulates that houses must have renewables (a very silly clause), and these are expensive – but this doesn’t fly either, for three reasons. Firstly, renewables aren’t always more expensive than the paraphernalia required by Passivhaus, and you certainly can’t assume they will always be more expensive in the future; secondly, it’s not completely clear-cut that Part L makes renewables compulsory at all4; and thirdly, even if it’s mandated by councils, the Passivhaus requirement is in addition to Part L rather than instead of it, and you can’t have it both ways – if you insist Part L requires renewables, then Passivhaus is also subject to Part L and must have them too. Since PHPP software doesn’t make any allowance for renewables, you will simply end up adding renewables you don’t really need. That’s the opposite of cost-effective.

So there can be as many articles as you like about why Passivhaus is as cheap or cheaper than a typical Part L house. It may well be good value, and not much of an extra cost. However, the claim that “Passivhaus is cheaper” has no credible evidence to back it up.

  • Passivhaus is Better-Ventilated

This is an area where I’ll cede ground. Passivhaus uses mechanical ventilation with heat recovery to ensure that its rooms are well-ventilated, which in turn prevents build up of water vapour and hence things like condensation. Ireland’s regulations on ventilation (Part F) are woefully out of date and not fit for purpose, so you’ve no guarantee that a typical new-build house will properly perform in this area. Architects and builders tend not to have comprehensive knowledge of ventilation – it tends to be the province of mechanical engineers, who aren’t usually hired for domestic jobs.

That, however, is an argument for updating Part F and/or for local authorities to introduce their own ventilation standards. It isn’t an argument to mandate Passivhaus. We know its model (mechanical ventilation) works, but which is not the only way of ventilating a house properly. You don’t have to have a mechanical ventilation system utilising heat recovery – indeed in an Irish climate, where we seldom have to deal with extreme highs and lows of temperature, it’s probably fair to say that it’s a rather perverse way of ventilating a building. Effectively mandating this is highly restrictive, and – again – not the sort of thing that should be written into law.


None of this is an argument to stop building Passivhauses. I think that, as a system, it’s fine (with some reservations) and I hope I get the chance to design one some day. However that doesn’t mean it should be rammed down everybody’s throats as the only acceptable way to build a low-energy house. If Passivhaus is really so efficient, so effective, and offers such good value for money, then it should thrive anyway. The fact of the matter is that there is a critical problem in Ireland that’s entirely centred around poor build quality, and Passivhaus will do nothing to alleviate that problem.

Nor will a narrow focus on the regulations that govern new-build houses do anything to manage climate change or conservation of Ireland’s resources. This is a big, all-encompassing issue that touches on every facet of Irish society and Irish infrastructure. Moving from low-energy houses to slightly-lower-energy houses will not solve that problem, it’s just a fetishisation of low U-Values and draughtsealing details for their own sake. I wouldn’t say that this is a bad thing, although I do find it limiting. However, there is no good reason to make it law, and it should not happen.

There is a broader point here. With Nearly Zero Carbon buildings due to become law in 2020, an update to Part L is surely around the corner. This is an opportunity for all building designers, whether advocates of Passivhaus or not, to come together and lobby the government for a sensible, improved TGD L that ensures good standards while at the same time being simple to understand for everyone, not the lumbering, cumbersome, complicated disaster of a document we currently have. That’s where the battle should be focused, for everyone’s benefit – including Passivhaus designers and builders. Going from council to council, getting them to make a particular construction system legal, is a waste of everyone’s time.

1. The wording permits alternatives, but uses Passivhaus as the primary standard. I don’t want to dwell on this aspect because it’ll make a long post longer, but I’ll simply say that I think the question of permitting alternatives is a red herring. At the very least, it gives Passivhaus a clear competitive advantage when it comes to compliance.
2. This is a slight oversimplification, but holds true as a rule of thumb.
3. I want to be clear that I’m not trying to blame builders here. On the contrary, I feel deeply sorry for them. The regulations have been updated very significantly and very suddenly, and builders have been given very little help to keep up with this. It’s an impossible situation to be in and I’m saying they need real support from the state, not blame.
4. TGD L gives a fixed amount of energy that needs to come from renewables, based on the floor area of the building. However the Guidance Documents are ultimately advisory, the actual law only states that “a reasonable proportion” of energy must be derived from renewables, and this is up for interpretation. I know architects who argue that DEAP is state-validated software for calculating a house’s energy use, so if their house is hitting the energy use targets required by DEAP without renewables then a “reasonable proportion” could even be zero. Personally, I think that’s a valid interpretation.

About Mike Morris

A British / Irish architect who practiced in Ireland and Ontario, now working in the U.K.
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One Response to Good System, Bad Law

  1. Martin Mallon says:

    Excellent article Mike, well done and well said. I am fed up of academics and certain media pushing Passivhaus down our throats.

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