As the built environment continues its transition towards net zero carbon, the term Nearly Zero Energy Building (NZEB) has become increasingly common in discussions around design, compliance, and sustainability. Yet for many clients, developers, and building owners, understanding what NZEB actually means and, why it matters can be challenging.
A Nearly Zero Energy Building is a building that has a very high level of energy performance, where the small amount of energy required is supplied, to a significant extent, by renewable energy sources.
The concept was introduced through the European Energy Performance of Buildings Directive (EPBD) and has become a key benchmark for improving the energy efficiency of both new and existing buildings.
In practical terms, an NZEB is designed to:
- Minimise energy demand through efficient building fabric and design.
- Reduce energy consumption through high-performance systems and controls.
- Utilise renewable energy technologies to offset operational energy use.
- Deliver comfortable, healthy internal environments while reducing carbon emissions.
The goal is to use as little energy as possible and ensure that the energy that is used comes from cleaner, renewable sources.
The building sector is responsible for a significant proportion of global energy consumption and carbon emissions. Improving building performance is therefore essential to achieving national and international climate targets.
NZEB buildings deliver a range of benefits beyond regulatory compliance, including:
- Reduced Energy Costs- Lower energy demand means reduced operational costs throughout the building's life.
- Lower Carbon Emissions- By reducing energy consumption and incorporating renewable technologies, NZEB buildings significantly reduce their environmental impact.
- Improved Occupant Comfort - High-performance buildings typically provide more stable indoor temperatures, better air quality, and improved occupant wellbeing.
Future-Proofed Assets - As regulations continue to tighten and energy prices remain volatile, high-performing buildings are better positioned to retain value and meet future requirements.
NZEB and the Journey to Net Zero
While NZEB represents a major step forward in sustainable building design, it is important to recognise that NZEB and net zero carbon are not the same thing. NZEB focuses primarily on operational energy performance and renewable energy contribution. Net zero carbon goes further by considering both operational and embodied carbon across the entire lifecycle of a building.
However, NZEB provides a critical foundation for achieving broader net zero ambitions. By prioritising energy efficiency and renewable energy generation, building owners can significantly reduce emissions while creating more resilient and cost-effective assets.
NZEB in Practice: citizenM Dublin St. Patrick's
While the principles of NZEB are straightforward in theory, achieving compliance requires a carefully balanced approach that considers building fabric, energy systems, renewable technologies, and operational performance. A strong example of this can be seen in the citizenM Dublin St. Patrick's Hotel where IN2 carried out detailed energy analysis and dynamic simulation modelling to assess and optimise the building's energy performance. The modelling considered climate conditions, building fabric, glazing, HVAC systems, occupancy patterns, and renewable energy contributions to ensure compliance with Ireland's NZEB requirements.
The final design strategy incorporated:
- High-performance building fabric to minimise heating demand.
- Air source heat pumps providing space heating, domestic hot water, and cooling.
- Mechanical ventilation with heat recovery to reduce energy losses.
- High-efficiency LED lighting with occupancy and daylight controls.
- Intelligent monitoring and control systems to optimise operational performance.
The project successfully achieved: - NZEB compliance under Part L 2017.
- An Energy Performance Coefficient (EPC) of 0.79.
- A BER A3 rating.
- An estimated 9 BREEAM Energy credits.
The project demonstrates that successful NZEB delivery is rarely the result of a single technology. Instead, it is achieved through an integrated design approach where building fabric, mechanical and electrical systems, renewable technologies, and intelligent controls work together to minimise energy demand while maximising building performance.
The future of building design will increasingly demand higher levels of performance, greater energy resilience, and lower carbon emissions. Nearly Zero Energy Buildings have already transformed the way buildings are designed and delivered across Europe, and they continue to provide a valuable framework for creating sustainable, efficient, and future-ready developments.