Navigating Part L Compliance: Key Questions Answered

In Ireland, achieving energy efficiency in buildings is a legal requirement. Part L of the Building Regulations, established by the Department of Housing, Local Government, and Heritage, sets the standards for energy performance and conservation in both new and existing buildings. Part L is sometimes also referred to as nZEB (Nearly Zero Energy Buildings).

Here, we answer some common questions about Part L compliance to help architects, property developers, and building professionals understand its importance and requirements. 

What is Part L?

Part L of the Building Regulations sets the standards for energy performance and conservation in buildings. It aims to minimise energy consumption and reduce greenhouse gas emissions by specifying performance requirements for areas such as building fabric, ventilation, space and hot water heating systems, lighting, control systems and renewable energy sources. Part L ensures that buildings are energy-efficient, sustainable, and contribute to Ireland’s goal of reducing energy & carbon emissions. 

Does every building have to comply with Part L?

Yes, all new buildings and existing buildings undergoing major renovations must comply with Part L of the Building Regulations. This compliance ensures that buildings meet the necessary energy efficiency and conservation standards. 

What building types are exempt from Part L?

Certain building types may be exempt from Part L requirements. These can include protected structures such as historical buildings, buildings of architectural significance, and specific types of agricultural buildings. For detailed exemptions, please refer to the Building Regulations documentation. 

What areas are looked at under Part L?

Part L covers several critical areas to ensure compliance:

  • Building fabric performance: This includes U-Values, thermal bridging, and air permeability targets. 
  • Ventilation strategies: Ensuring adequate ventilation while minimising energy requirements. 
  • Space heating and hot water systems: Standards for efficient heating systems. 
  • Artificial lighting: Use of low-energy lighting. 
  • Control systems: To properly controls the building systems within the building 
  • Renewable energy sources: Incorporation of renewable energy to meet a portion of the building’s energy demand. 

    How do you show Part L compliance? 

    Part L compliance involves several steps: 

    • Design Stage: Incorporate features of the proposed building designs using building modelling software (DEAP for Domestic Buildings and NEAP for Non-Domestic Buildings) to produce a preliminary Part L compliance report. 
    • Construction Stage: Adhere to approved designs and specifications, ensuring best practices. 
    • Completion: Conduct air tightness testing and final site inspections of the building and update the building model using the modelling software. A Part L compliance report will be completed along with a BER (Building Energy Rating) assessment. A BER Certificate will be produced which will be provided to the client. 
    • Occupancy and Maintenance: Maintain energy-efficient systems and monitor energy usage for ongoing compliance. 

    What triggers major renovations under Part L for non-domestic buildings?

    Major renovations under Part L are triggered when more than 25% of the surface area of the building envelope undergoes renovation, the energy performance of the whole building should be improved to Cost Optimal level in so far as this is technically, functionally and economically feasible. 

    What are the electric vehicle recharging infrastructure requirements?

    Part L requires buildings to provide infrastructure for electric vehicle recharging. This includes pre-cabling and other preparatory work to facilitate the future installation of recharging points, supporting the growing use of electric vehicles. 

    For non-domestic buildings including major renovation projects where there are more than 10 car parking spaces in or adjacent to the building. The following minimum electric vehicle recharging infrastructure should be provided:   

    • At least 1 recharging point, and 
    • Ducting infrastructure, consisting of conduits for electric cables, for at least 1 in every 5 car parking spaces, or part thereof, to enable the subsequent installation of recharging points for electric vehicles.

    For domestic buildings (containing one or more than one dwelling), ducting infrastructure, consisting of conduits for electric cables, should be provided for every parking space, to enable the subsequent installation of recharging points for electric vehicles. 

    Do you need to install a heat pump? 

    While installing a heat pump is one option to meet Part L’s renewable energy requirements, it is not mandatory. Other renewable energy sources, such as solar panels or biomass boilers, can also be used to comply with the regulations. 

    How do you meet the renewable energy requirements? 

    To meet the renewable energy requirements of Part L, buildings must source at least 20% of their energy from renewable sources. This can be achieved through the installation of solar panels, heat pumps, biomass boilers, or other renewable technologies onsite or nearby. 

    For non-domestic buildings the renewable requirement can be reduced to 10% if the Energy and Carbon performance of the building brought to an improved standard.


    Compliance with Part L is essential for promoting energy efficiency and sustainability in the Irish building sector. By adhering to the regulations outlined in Part L, building owners and developers can contribute to a greener future, ensuring their buildings are energy-efficient and environmentally friendly. This not only helps in reducing carbon emissions but also offers numerous benefits such as lower utility bills, improved indoor comfort, and adherence to legal standards. 

    The ORS Energy Management team provides Part L (nZEB) compliance services, ensuring buildings meet the highest energy performance standards. Our team provides expert guidance on regulatory requirements, enhancing energy efficiency and sustainability in building design and operation. 

    For more information and guidance on Part L (nZEB), please contact the Energy Management Team at ORS.

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