LEED Energy & Daylight Modelling for An Post’s Platinum HQ

Hello, Champions of Net Zero!
We are thrilled to share an inspiring development from Dublin that marks a significant milestone in sustainable architecture and energy efficiency. Standing tall at 17 storeys, the Exo Building has proudly claimed the title of the tallest office building in Dublin’s vibrant docklands. This architectural marvel is not just a striking feature on the skyline; it is a beacon of sustainability, boasting a near-zero energy building (NZEB) designation. In fact, it ranks in the top 2% of the most sustainable buildings worldwide, holding both the prestigious LEED Platinum certification and a Building Energy Rating (BER) of A3.
As the anchor tenant of this landmark structure, Ireland’s national postal service, An Post, has embraced the future with a lease of six floors within the Exo Building, covering a serviced floor area of 7,680 square metres. This move not only signifies a commitment to modernity but also a pledge towards eco-conscious business operations.
To ensure the building’s fit-out meets the high standards required for its LEED Platinum certification, An Post engaged IES Consulting in 2022. IES was tasked with providing comprehensive LEED energy and daylight modelling services, which are crucial for achieving high levels of energy performance. Additionally, IES assumed the role of Commissioning Authority (CxA), ensuring that the energy-efficient design intent is seamlessly integrated into the building’s operational phase.
LEED Energy Modelling: A Step Towards Sustainability
The journey towards attaining LEED Platinum certification under the LEED v4 ID+C Commercial Interiors Development rating system began with meticulous energy modelling. IES consultants conducted the LEED PRM energy modelling for the fit-out of the leased spaces, adhering to the ASHRAE 90.1 Appendix G (Performance Rating Method) 2010 standards and utilising the IES Virtual Environment (VE) software.
The Exo Building features an impressive window to wall ratio (WWR) of 74.6%, which, combined with a diverse array of room types and systems, has a significant impact on overall energy performance. A preliminary energy model was prepared for the base building as part of the LEED Core & Shell (C&S) submission. This model was adapted to analyse the energy efficiency measures relevant to the tenant fit-out.
The building incorporates a range of high-efficiency design features, which were scrutinised during the design process for both the base building and the tenant spaces. Key considerations for the base building included:
- Thermal performance of building fabric
- Energy recovery for outdoor air handling units (AHUs)
- High-efficiency condensing boilers
- High-efficiency scroll chillers
- Variable speed drives for secondary chilled and hot water pumps
For the tenant fit-out, the focus shifted towards internal load reduction, as opportunities to influence central HVAC systems and external shading were limited. The analysis encompassed:
- Efficiency of interior lighting in tenant areas, aiming for savings beyond the stipulated maximum lighting power density of 8W/m²
- Specification of energy-efficient office appliances
- Supplementary fan coil unit specific fan powers (SFPs)
- Water-efficient fixtures and fittings
All these features underwent thorough investigation within the energy model to evaluate their contribution towards meeting the client’s energy performance targets. The analysis also considered the economic viability of each measure, allowing the design team to engage in informed discussions regarding the feasibility of the design and the best pathways to achieve the desired objectives.
Thanks to this meticulous analysis, IES demonstrated a remarkable combined energy cost saving of 27.3% over the ASHRAE 90.1 2010 baseline, which translates to an impressive 24 EAc1 points under the LEED v4 ID+C: Commercial Interiors Development rating system.
LEED Daylight Modelling: Harnessing Natural Light
In addition to energy modelling, the IES team was tasked with providing daylight modelling services aimed at achieving the LEED v4.1 EQ Daylight credit. This critical aspect requires the utilisation of Climate-Based Daylight Modelling (CBDM), a dynamic approach that surpasses basic static calculations to determine how daylight performance varies across building spaces throughout the year.
Utilising the RadianceIES application within the VE, IES conducted an annual simulation that integrated location, shading, and climate data along with the building’s physical properties. The analysis took into account various solar shading devices, whether internal or external, and included manual or automatic controls to regulate daylight levels entering the space. The metrics employed to assess daylight performance included Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE), necessitating individual simulations for all regularly occupied spaces throughout the calendar year.
This rigorous analysis positioned the IES consultants to demonstrate that a maximum of three points could be achieved for the LEED v4.1 Daylight credit, further solidifying the building’s sustainability credentials.
LEED Commissioning: Ensuring Performance Excellence
To guarantee that the building’s high-performance design intent carries through into its operational phase, IES Consulting was appointed as the LEED Commissioning Authority (CxA) and overall manager of the commissioning (Cx) process for the An Post Headquarters. This process adhered to LEED ID+C v4 EA Fundamental Commissioning & Verification and EA Enhanced Commissioning Option 1 standards.
IES was responsible for the formulation and compilation of the commissioning plan, alongside all necessary documentation requirements. The scope of commissioning included functional performance testing (FPT) for energy-consuming systems, ensuring that the building operates efficiently and aligns with its design intent.
The commissioned systems encompassed:
- HVAC Systems: Fan Coil Units, Air Handling Units, Heat Recovery Units, and Pumps
- Lighting and Lighting Control Sensors
- Domestic Hot Water (DHW) systems and under-sink water heaters
- Electrical Distribution systems
- Building Management System (sensors, valves, and local control devices)
Throughout the final commissioning process, IES coordinated with various contractors to address any issues identified, ensuring optimal operation of the building systems. This included refining operational procedures to meet the owner’s best interests, adjusting or replacing defective components, and completing all contractor documentation requirements. Notable challenges included the replacement of filters on the AHUs, ensuring the correct configuration of an A/C unit flagged by the Building Management System (BMS), and rectifying a fault with one of the extract fans.
The commissioning process is a fundamental step in ensuring that a building performs in line with its design intent and meets all specification requirements. However, it is crucial to ensure that the operational performance does not drift over time. While the consultants were satisfied that the commissioning process had ensured proper installation, calibration, and training for efficient building systems operation, the ongoing commissioning plan provided to the client will play a vital role in maintaining the building’s operational efficiency well into the future.
In conclusion, the Exo Building stands as a testament to what can be achieved when innovative design meets a commitment to sustainability. As we move towards a net-zero future, developments like this not only inspire but also set a benchmark for future architectural projects. The collaboration between An Post and IES Consulting exemplifies the importance of integrating energy efficiency and sustainable practices into the very fabric of our built environment. Together, we can champion the cause of net-zero buildings and create a brighter, more sustainable future for all.
Stay tuned, Net Zero News Community, for more updates on sustainable innovations and developments shaping our world!