Key questions on the implications of making passive house mandatory

Key questions on the implications of making passive house mandatory

Dun Laoghaire-Rathdown County Council’s proposal that all new buildings in the county must be passive houses or nearly zero energy buildings (NZEBs) is currently out to public consultation till 11 May. But what is this proposal all about, and what are the implications?

What is passive house, and what makes it so special?

It’s a science-based construction standard, created to all but eliminate the need for heating systems in buildings, meaning miniscule heating bills while simultaneously ensuring high comfort levels, indoor air quality and durability.

The Intergovernmental Panel on Climate Change's 5th assessment report (2014) singled out the passive house standard as one of the key climate change mitigation options available for buildings. Endorsements don't get much better than that.

The passive house standard was created by German and Swedish scientists and engineers 25 years ago, based on sound theoretical principles and on studying why earlier European and North American attempts at low energy building had failed. Since then its efficacy has been supported by masses of monitoring on everything from energy usage to indoor air quality. Attempts at low energy building have a long history of failing to deliver, with a performance gap existing between designed and actual energy use for a variety of reasons. And what’s the point investing in energy saving if it doesn’t actually perform?

How big a problem is this performance gap?

Estimates vary greatly, but UK studies indicate that non domestic buildings may be consuming up to or more than twice the amount of energy predicted at design stage [1], with dwellings seeing up to 100% higher heat loss than predicted [2]. According to a source in SEAI, Irish homes that have received energy upgrade grants have seen performance gaps of 30 to 70%, with higher disparity in fuel poor households.

Show/hide more on this question

Passive houses on the other hand appear not to suffer from the performance gap. A review by English architect Mark Siddall of post occupancy heating data on 228 passive houses showed a mean heating consumption of 15.45 kWh/m2/yr – exactly in line with the space heating target for passive houses. [4]

Why don’t passive houses suffer from a performance gap?

Probably for several reasons. First of all, the buildings tend to almost run themselves. Writing in The Guardian [5], editor Lloyd Alter summed this up eloquently:

“I suspect that people are happier in stupid houses, stupid buildings and stupid cities. Take a Passivhaus for example. These houses don't have a whole lot of green gizmos; just a whole lot of insulation and carefully designed and placed high quality windows. The temperature doesn't change much inside; a smart thermostat would be bored stupid.”

Secondly, the passive house software (PHPP) is designed specifically for low energy buildings. Ireland’s national methodology, DEAP, on the other hand, is used to generate BERs for everything from 100 year old buildings with no insulation, no central heating and leaky single glazing, to brand new experimental eco homes packed to the gills with insulation and green technology.

Show/hide more on this question


Won’t making passive house mandatory cause construction costs to rise?

No, not in Ireland. Since 2011 new homes have been required to hit 60% energy reductions, which typically means a mid A3 BER – and in some cases even an A2. This means construction costs are now in passive house territory, so it’s questionable whether there’s any extra cost at all. One recent scheme indicates passive house can be delivered at highly competitive prices. Developer builder Michael Bennett & Sons are offering A2 rated certified passive three bed semi-ds for sale in Enniscorthy for just €170,000 each. The homes will be over 1100 sq ft each, and come with a guarantee that heating/hot water bills will be no more than €200 per annum.

Show/hide more on this question


But will it cause house prices to increase?

No. The market determines what price a given property’s worth. Developers won’t be able to charge extra for passive houses – even if they’re arguably worth more – unless buyers are willing to pay more. Even if that is the case, it’ll only be a question of how much more buyers are willing to pay for passive houses relative to other new homes, which are also legally obliged to be highly energy efficient (the average dwelling has to hit a mid A3 BER just to comply, and many apartments even have to hit A2).

Show/hide more on this question


Is passive house a threat to traditional construction methods?

Not in the slightest. The passive house standard is essentially open source and can be built using virtually any construction materials and methods. To date in Ireland, passive houses have been built using cavity wall construction, timber frame, steel frame, single leaf masonry with external insulation, structural insulated panels, insulating concrete formwork and even hempcrete. It’s just a question of careful detailing and workmanship to ensure continuity of insulation, airtightness and a seamless ventilation approach. The industry may not be aware of this yet, but the real threat to traditional construction surely exists in trying to meet stringent theoretical energy targets in building regulations without being informed by building-science based, quality assured approaches such as passive house. Throwing insulation and gadgetry at a building without due care for the consequences is a dangerously misguided approach.

But don’t you have to use imported skills and products to build passive houses?

Again no. Some of Ireland’s biggest construction product manufacturers have passive house solutions, including Kingspan, Munster Joinery, Coillte, Xtratherm, Isover Ireland & Quinn. There’s a plethora of Irish build system and insulation manufacturers with passive house solutions, along with heat recovery ventilation systems, airtightness products and passive certified triple glazed windows. And we have over 300 certified passive house designers and counting, and the most certified passive house tradespeople of any country in the world. Note that you don’t have to be a certified designer or tradesperson to build a passive house, but it helps to ensure hitting the standard without a hitch, and as cost-effectively as possible.

But how will I breathe in such an airtight house?

Better than in most houses, actually. Airtightness is a much misunderstood subject. It’s not about eliminating ventilation from buildings – it’s about removing unintended leakage through constructional inaccuracies. The mantra is build tight, ventilate right. Properly designed, installed and commissioned ventilation systems are inherent to passive houses – but worryingly not to the theoretically low energy buildings required by building regulations. And as a recent UK study has demonstrated, this is a foolish oversight. Higher energy efficiency scores in homes are associated with a statistically significant increase in asthma diagnoses [8], because most energy efficiency efforts don’t come with fit-for-purpose ventilation strategies.

Show/hide more on this question


Is it true that passive houses don’t require heating systems?

No it’s not. They do require some active heating input at times – as well as domestic hot water, assuming you want to maintain basic hygeine standards. But they require much smaller heating systems, that are used less frequently. So innovative heating technology suppliers can breathe a sigh of relief, while energy suppliers could quite reasonably break out in a cold sweat.

Show/hide more on this question


Okay you have me now. Are there any other benefits?

Absolutely. Where to start… This is anecdotal, so take it with a fistful of salt, but passive house occupants report that they rarely if ever have to dust any more (due to the wonders of a ventilation system that shifts air – and therefore airborne particles regularly), that they get sick less often than in previous homes, that you don’t get spiders in them. That’s without even getting into the absurdly low heating bills, the higher comfort levels and the fact that taking a robust, fabric first approach locks in these benefits – and all the embodied carbon in construction – for generations to come, rather than less considered approaches with an over-reliance on technology with perhaps 20 year lifespans, and poorly detailed and executed construction approaches which may lead to costly repair and replacement work.

So what do you want from me?

Sign our petition to help fight climate change and kick start an Irish market for warm, healthy well-built buildings that cost half nothing to heat.

Click here to sign the petition.


Click here to view information on the development plan, including how to make an online submission. It's not just constituents who can make submissions - anyone can, whether based in Ireland or further afield. So feel free to encourage your colleagues, friends and family members, whether here or overseas to make submissions.

Passive house is mentioned in two chapters. Click here for the chapter including the main reference (on p139), and also click here for the chapter that includes a definition of passive house (on p215).


Last modified on Wednesday, 13 June 2018 12:08

Marketplace + companies featured in this article

Isover Ireland

ISOVER is part of Saint-Gobain, world leader in designing, manufacturing and distributing building materials.

Dublin, County Dublin
View details
Munster Joinery

At Munster Joinery, we hold the highest number of passive house certified windows of any window company globally.

Beattie Passive

We simplify Passivhaus to deliver energy efficient and sustainable modular homes