Defining what constitutes a NZEB building has become something of a regulatory minefield. There are at least 28 different national definitions for NZEB (29 if you include the EU Commission’s) and all sorts of derogations, implementation trajectories and greater or lesser buy-in from political leaders.
In Ireland, for example, 3 different definitions of NZEB currently apply to housing, ranging from 60 to over 500kWh/m2a, as follows:
- A new-build house is required to meet Part L, 2011 (approx. 60kWh/m2a) including a 10kWh/m2a on-site renewable energy generation requirement
- An existing house which is to be fully refurbished is required to meet the backstop U-values in Part L, 2011 (typically 150-75kWh/m2a) but doesn’t have a renewable energy requirement
- A house undergoing maintenance works (including full-scale rebuilding after pyrite, mica or fire damage) doesn’t have to meet any efficiency requirement unless the boiler is being replaced, in which case minimum boiler efficiency has to be achieved, certain pipework has to be insulated and certain controls fitted.
All three of these can be regarded as NZEB buildings as they meet the minimum threshold for building regulations compliance for energy efficiency in Ireland. Northern Ireland has its own, entirely separate, suite of NZEB definitions as do England, Scotland and Wales. Similar sub-national cantonisation of the definition applies across the EU.
In July 2016, the EU Commission issued a recommendation which is breath-taking in its simplicity: there is to be a common EU definition for NZEB. It is to be adjusted for 4 European climates zones.
Under this recommendation (EU 2016/1318) the minimum Irish NZEB standard is to be 15-30kWh/m2a for housing (new or existing). There is to be no difference between new-build and refurbishment: governments have to bring up the entire stock up to this single standard.
To put this in context, an Irish certified Passive House measured in DEAP achieved 53kWh/m2a, which would not be untypical, so the proposed NZEB standard is close to twice as good as the Passive standard.
In one short document, 15 years of regulatory complexity and political foot-dragging is to be swept away and replaced by clarity. But only if Ireland accepts the Commission’s recommendations.