Here at nZEBRA, we can cater for all your building fabric & energy performance requirements. Whether you need U-values calculated, BER calculations, Passive House (PHPP) calculations, condensation risk analysis or full design specification, we can offer you a tailor-made package to suit your requirements. Our specialist team here in nZEBRA have worked extensively in the field of low-energy & Passive House design, in fact we have over 85 years combined experience in low-energy building design, specification & assessment. We can partner with you to bring your designs to fruition, ensuring cost-optimal building designs and delivering low-energy, Passive or nZEB-level performance.

What is nZEB?

nZEB, or ‘nearly Zero Energy Buildings’, was introduced under the recast-EPDB (European Performance of Buildings Directive) 2012 (2010/30/EU). This document is a revision to the existing EPBD (2002/91/EC) which was transposed into Irish law in 2006. In terms of Irish statutory legislation, the Statutory Instrument 666 2006 was superceded by S.I. 243 of 2012.

The main requirements of the EPBD were as follows:

  • Introduction of a method calculate and rate the energy performance of buildings.
  • Introduction of a system whereby new and existing buildings could be certified, with a requirement for Display Energy Certificates to be shown in public buildings.
  • Mandatory regular inspections of plant including heating & air-condition systems.
  • Minimum energy requirements for the renovation of existing buildings, or design of new buildings, with floor areas of less than 1,000m2.

Current Part L (2011) requires a 60% improvement in Primary Energy Consumption relative to an equivalent building constructed to the 2005 Part L requirements. This equates to an EPC (Energy Performance Co-efficient) of 0.4, where the 2005 value sets a baseline EPC of 1.0. The typical BER rating of a newly-constructed dwelling is A3. The table below outlines the nZEB requirements established in Ireland in order to satisfy the requirements of the recast EPBD (2012).

Technical Guidance Document Part L 2005 2008 2011 nZEB
Energy reduction (%) Baseline 40 60 January 1st 2021
Primary Energy Consumption (kWh/m2.annum) 150 90 60 45
CO2 emission rate (kgCO2/m2.annum) 30 18 12 10
Maximum Permitted Energy Performance Coefficient (EPC) 0.6 0.4 0.302
Maximum Permitted Carbon Performance Coefficient (CPC) 0.69 0.46 0.305
BER rating B3 B1 A3 A2

For non-domestic buildings, it is envisaged that an improvement in primary energy consumption of 60% relative to the current requirements of Part L (2008) – Buildings other than dwellings, will be required to demonstrate compliance with nZEB.

What is DEAP?

DEAP, also known as the Dwelling Energy Assessment Procedure, is a methodology and software tool introduced in response to the EPBD requirements transposed into Irish law in 2006. It is the calculation method which is the foundation of the BER assessment for new and existing dwellings. The software tool and associated documents can be downloaded for free here (

DEAP is referenced in the Second Schedule of the Irish Building Regulations Part L (S.I. 259 of 2011) as the required method for assessment the building energy performance of buildings. As such, it is proposed that a revision of DEAP, as well as the associated methodology and Technical Guidance Document (Part L) will be used to form the basis of determining nZEB design performance and ensuring compliance the recast EPBD (2012) is achieved.

What is Passive House?

The Passive House standard

There are different interpretations on what constitutes a ‘Passive House’. However, nZEBRA uses only the definition provided by the Passivhaus Institut in Darmstadt, Germany, as follows:

  • Maximum annual space heating requirement of 15kWh per square metre: 15kWh/(m2a)
  • Minimum airtightness of 0.6 air changes per hour measured at a pressure of 50 Pascal: n50 0.6 1/h
  • Maximum annual primary energy requirement of 120kWh per square metre (domestic hot water, heating and auxiliary electricity): 120kWh/(m2a)
  • Optimal heat load of 10 W per square metre: 10W/m2
  • Achieving the first three of the above is required for official Passive House Certification. The optimal heat load above should be achieved if you wish to heat your home via the mechanical ventilation system

What is the PHPP?

The PHPP is the software tool used by Passive House designers and consultants to determine whether a building achieves the requirements of certification. The PHPP carries out an energy balance calculation to determine annual heat demand, heat load, ventilation requirements, primary energy consumption, electrical energy consumption, as well as energy requirements for plants/services. The performance is measured based on the buildings fabric performance levels, air-tightness, as well as orientation, shading specific location and elevation. The software is Excel-based, and also uses a SketchUP plugin which allows the building geometry to be quickly modelled and exported to the Excel calculation.


About Us

nZEBRA is a solution provider for all your nZEB needs. Our team has been operating in this space for over a decade and has the right balance of science and real-world application.
We have a proven track record of delivering fast-track affordable nZEB projects for both private and public sector

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Wicklow County Campus
Clermont House, Rathnew
County Wicklow, A67 X566, Ireland

+353 (0) 404 25777

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