Opinion - Is passive house going mainstream?

Is passive house going mainstream? As building standards move towards passive house and rising fuel prices prioritise minimising running costs above any other consideration, one can be forgiven for assuming that the era is almost upon us when all Irish buildings – residential, commercial and public – will be built to a certified passive house standard. But is this a realistic assumption? One thing is certain, it is a tantalisingly desirable aspiration for us in the construction and design industry and would at once reinforce our position as early adopters and the leaders of passive house in the English speaking world, while simultaneously healing the damaged image of our construction industry and opening up export markets for our knowledge, skills and products. But in any potential advance towards a universal application of passive house there are many issues to be considered.

The first issue, quite naturally in our era of austerity is the capital cost of a passive house build. It would be far too simplistic to take a range of passive house buildings and put a figure on the extra cost, over a conventional building which barely complies with the 2008 Building Regulations. Cost depends on a multitude of considerations, not least the fact that in the private residential sector, passive house clients generally insist on high quality fixtures and fittings. If the windows were to cost €15,000 more than basic standard, do you attribute that extra cost purely to achieving the energy standard or are you paying extra for better functionality, aesthetics and longevity?

Clients and designers aspiring towards passive house have a very clear idea of the budget limitations affecting their project and the space requirements that the budget will deliver. In many cases, incremental improvements which move the design towards certification are halted just shy of the passive house threshold for space heating demand of 15kWh/m2/yr. There are many reasons why some projects are just not suitable candidates. Despite the best efforts to optimise design and energy modelling, some will always fall short of being candidates for certification. Having a heat demand slightly higher than the threshold, at say 18kWh/m2/yr may have slightly higher running costs, but they’re minimal when compared with capital costs of finding the final 3-5kWh in some cases. Every project has a capital expenditure versus running costs sweet spot, when the site conditions and design strategy yield a performance for heat demand that falls inside the passive house criteria (with some contingency to spare of course) then certification becomes a simpler proposition. If however, you miss the threshold by a few kilowatt hours, meaning you’re unable to deliver the space heating solely through the ventilation system – the rationale for the standard – it is still a high performance building and the addition of a couple of radiators and towel rails are always useful if someone’s idea of thermal comfort in a bathroom is 23 degrees rather than 20. With unusually cooler winters predicted for the coming decade, having some additional discretionary heat is no bad thing.

Archie O’Donnell, projects coordinator for Éasca and the Irish Passive House Association

The second issue – design – is by its nature subjective and divisive. It is welcome to see a high number of architect-designed bespoke homes being certified, but it is difficult to envisage a time when pattern book type designs are replaced with homes designed to optimise site and energy performance. While this issue proves that passive house can be adopted to every conceivable style of building, the emphasis placed by the passive house modelling tool on compactness and simplified footprint buildings could place added expense on those restricted to single storey buildings by planning or access considerations. Planners must also be educated to recognise a new typology of building that does not necessarily face the road and may deviate in form from designs favoured to date in local authority design guides. The debate about whether or not ultra low energy buildings will necessitate a new design language and how they will contribute to urban and rural landscapes, is complex.

The third issue – regulatory compliance – is concerned with the recognition of passive house (or lack thereof) in building regulations. It seems almost perverse to have two parallel energy performance methodologies with mutual objectives to substantially reduce energy use but conflicting methods. While passive house prioritises minimisation of heat loss above all else, the Deap methodology for Part L compliance is less stringent on fabric and ventilation heat loss and puts a disproportionately high emphasis on the use of renewables. Part L 2011 will come into effect in December with enhanced standards of performance required. An appropriate building control mechanism similar to that provided by local authorities in the UK is necessary and can be supported by our local authority architects and engineers. Passive house, with an onerous certification process requiring on-completion air leakage testing and evidence of installed insulation, provides a model for inspection of low energy builds to ensure that adequate attention to detail is applied. One proposed solution is that the passive house standard could be recognised as an alternative method of compliance with the new Part L. This could feed into a possible strategic move by government to support the potential of the ultra low energy and passive house building sector in Ireland.

The fourth issue concerns knowledge of passive house building. We need to work to correct misconceptions of passive house and spread the good news story that buildings which aspire to or achieve the passive house standard and its retrofit equivalent, EnerPHit, are reinvigorating the built environment and creating buildings that work. The job of ownership and dissemination of this knowledge needs to be taken up by our Irish Passive House Association members and we somehow need to secure funding for research of new more cost-effective materials and technologies and to monitor the buildings already complete and in use.

We may never get to the stage where every new building and renovation is a certified passive house. But it’s not the achievement of certification that’s important – It’s the aspiration to go as far as practical within the limitations of every project. Let’s make all our building practically passive house, and accept no less than ultra low energy buildings.