The proposed changes to Parts L and F of the ROI Building Regulations were debated at the SEAI Energy Show’s Overcoming the challenges of NZEB and Major Renovation workshop on the 18th April 2018. Here are our findings.

  • The updated Parts F and L of the building regulations are expected to take effect in April 2019, subject to a transition period. The transition period foresees that the previous regulations will continue to apply to those dwellings that have secured planning permission before April 2019 and that have built the house up to wall plate level by the 31st March 2020. The final version of the regulations, post public consultation, are expected to be published in July of this year with the revised Dwellings Energy Assessment Procedure (DEAP – the software used to calculate compliance with Part L of the building regulations) published in September.
  • There is a focus in the draft regs on the importance of commissioning and on the need to provide the end-user with information about how the house works and how to maintain the building services, e.g. how and when to change filters in mechanical ventilation systems.
  • “Design data” will be made available from Met Eireann, announced Minister English in his opening address, presumably to help designers specify the thermal envelope and the ventilation strategy*.
  • Consultants AECOM claim that houses built to the draft Parts L and F present a minimal risk of overheating, which they say can readily be dealt with by making better use of curtains and blinds.
  • Uplift in costs between the previous versions of the regulations and the current draft regulations is between 0.7 and 4.2 per cent, according to consultants Currie & Brown who did the cost analysis for AECOM.

Part L: Energy

  • For new builds Part L 2018 versus Part L 2011 will see the Building Energy Rating go from an A3 to an A2.
  • Backstop value for airtightness reduced from 7 to 5 m3 per hour per sqm at 50 Pa.
  • U-values reduced from 0.21 W/sqmK for all building elements (walls, roof, floor) to 0.18 W/sqmK which implies 150mm cavity walls as the new standard.
  • The draft Renewable Energy Requirement is envisaged to be increased to 20 per cent which means either a heat pump or gas boiler with PV panels will be the two cost optimal options open to self-builders. Renewables refer to heat pumps as well as biomass, solar photovoltaic (PV), solar thermal, CHP, and the renewable component of district heating, among others.
  • Minimum U-values for windows and doors set at a strict 1.4 W/sqmK (removal of permitted variations) and even though this represents the best performing type of double glazing, triple glazing is envisaged in many of the ‘regs compliant’ scenarios the Department has published. The Department of Housing’s Sean Armstrong pointed to triple glazing likely to be required “in a lot of cases”.
  • Space heating controls (zoning and time controller) requirement.
  • As previously announced, for renovations of 25 per cent or more of the building, an energy upgrade of the house will have to take place to bring it to the cost optimal level of a B3 or in the case of an external wall renovation:

Every year approximately 1.5 per cent of the housing stock undergoes renovation.






  • The calculations in the revised DEAP will be more favourable to heat pump technology, according to the SEAI’s Orla Coyle. The draft DEAP also envisages penalising extensive artificial lighting strategies and plans to make provisions for dual heating systems (currently you must choose a primary heating system). Hot water calculations will be more fined tuned by taking into account things like flow restrictors on showers reducing hot water demand. Another proposal is for the Primary Energy Factor to no longer be updated on a yearly basis but be based on projections and renewed every three to five years.
  • To achieve compliance there are two stages: overall compliance (that the building complies to nZEB calculations, equivalent to a 70 per cent reduction on 2005 requirements) and minimal threshold compliance (maxmium U-values, etc.). In addition, Construction Quality and Commissioning will have to be fulfilled as well as a document produced for the end-user’s information.

Part F: Ventilation

  • The draft regulations make it mandatory that the ventilation system, whether natural or mechanical, be certified (validated and checked) by an independent third party (not the installer of the system), such as an airtightness tester. The biggest issue with ventilation, Armstrong said, was to do with incorrect design and commissioning, including incorrect installation and balancing.
  • Ease of use is part of the requirement and this includes easy servicing, so best practice indicates that a mechanical unit must not be installed in an attic but instead in a place that’s easy to access to change the filters.
  • Much more detailed guidelines are provided for all ventilation types, including for installation and commissioning.
  • The draft Part F continues to allow for natural ventilation but only within a tight airtightness band of between 3 and 5 m3 per hour per sqm at 50 Pa. This means that the current requirements for natural ventilation under 5 m3 per hour per sqm at 50 Pa continue to apply (roughly achieved with 5 inch vents in every room). Any value below 3 requires mechanical ventilation as the whole house solution.


*UPDATE 19th April 2018 from the Dept of Housing in relation to the work of Met Eireann in supplying design data: “The National Standards Authority of Ireland, Met Eireann and Department of Housing Planning and Local Government  supported by Department of Communications Climate Action and Environment have a working group in place to review appropriate meteorological data used in standards related to building design.  The group is currently developing a scope of review which is expected to include a review of driving rain intensity data and development of climatic data related to estimating the effects of solar gain in buildings for Ireland. It is proposed that the output of this review will include consideration of appropriate meteorological data which is affected by climate change as outlined in the National Adaptation Framework.”