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.

House model on papers

In Ireland, for example, 3 different definitions of NZEB currently apply to housing, ranging from 60 to over 500kWh/m2a, as follows:

  1. A new-build house is required to meet Part L, 2011 (approx. 60kWh/m2a) including a 10kWh/m2a on-site renewable energy generation requirement
  2. 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
  3. 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.

 


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There are 2 comments

  1. Simon McGuinness says: February 10, 2017 at 9:25 pm

    A further definition of NZEB for housing was advised on 30 January 2017 by the Department of Housing, Planning, Community and Local Government. The 2021 definition of NZEB for housing will, apparently, be a dwelling with an MPEPC of 0.30 and an MPCPC of 0.35, both as measured in DEAP.

    It seems that this new definition falls some way short of the Commission Recommendation of July 2016, so maybe it should be regarded as yet another staging post along the scenic road to a final NZEB definition?

    Recently, 12 different houses were assessed by a team of postgraduate students at DIT, all of which achieved the 30kWh/m2a Commission recommended target using various energy systems and forms of construction. Not one seemed able to deliver the 30kWh/m2a minimum performance target by using an MPEPC of 0.30 or an MPEPC of 0.325.

    There may be an amendment of DEAP involved in this new formulation which will permit a house with an MPEPC of 0.30 and a MPCPC of 0.35 to achieve the Commission’s target of 30kWh/m2a.

    We await details from the Department.

  2. Tomas O’Leary says: February 13, 2017 at 2:10 pm

    Thanks for this overview – very interesting.
    I’d be interested to see more detail on how you reached the conclusion that nZEB will be twice as good as Passive House.
    The software used for nZEB (DEAP) and Passive House (PHPP) are completely different and so comparing them directly is (next to) impossible.
    I would find it hard to believe that Passive House with triple pane windows (U-value < 0.85 W/m2K), 0.6 ACH at 50 Pascal airtightness, U-values generally below 0.14 W/m2K and typically 90%+ heat recovery efficiency would use twice as much energy as an nZEB home.