Trial / Demo
Comprising 17-storeys in total, the Exo Building in Dublin’s docklands currently stands as the city’s tallest office building. Offering panoramic views across the city, the striking near-zero energy building (NZEB) is reported to be in the top 2% of buildings in the world in terms of its sustainability, holding both a LEED Platinum certification and Building Energy Rating (BER) of A3.
As the anchor tenant of this landmark building, Ireland’s national post service, An Post, has leased 6 floors of the Exo Building for its new headquarters, taking up a total serviced floor area of 7,680m2.
In 2022, they appointed IES Consulting to provide LEED energy and daylight modelling services to ensure high levels of energy performance in the building fit-out. To further support the project’s LEED Platinum certification, IES were also appointed as the as the Commissioning Authority (CxA), to ensure the high energy efficiency design intent is carried through into the operation of the building.
To help the client attain their desired Platinum certification under the LEED v4 ID+C Commercial Interiors Development rating system, the consultants initially carried out LEED PRM energy modelling for the fit-out of the tenanted spaces. The modelling was conducted in accordance with ASHRAE 90.1 Appendix G (Performance Rating Method) 2010, using the IES Virtual Environment (VE) software.
This building has a high (74.6%) window to wall ratio (WWR) and encompasses a variety of different room types and systems, all of which impact on the overall energy performance.
A preliminary energy model was prepared for the base building as part of the LEED Core & Shell (C&S) submission, which was adapted and used to analyse the energy efficiency measures applicable for the tenant fit-out. The building incorporates a range of high energy efficiency design features, the following of which were analysed during the design process for both the base building and tenant spaces:
Base Building Scope:
Tenant Scope:
For the tenant fit-out there was a greater focus on internal load reduction due to the limited opportunities to affect the central HVAC systems, envelope and exterior shading.
All these features were subject to detailed investigation within the energy model to ascertain their role in meeting the client’s energy performance target. The analysis also considered the economic viability of each measure, with other factors surrounding the overall feasibility of the design being discussed with the design team, to allow the client to make informed decisions on how best to achieve their objectives.
Through this analysis, IES were able to demonstrate a combined energy cost saving of 27.3% over the ASHRAE 90.1 2010 baseline, equating to 24 EAc1 points under the LEED v4 ID+C: Commercial Interiors Development rating system.
The IES team were also asked to provide daylight modelling services, to help the project achieve the LEED v4.1 EQ Daylight credit. This requires using Climate Based Daylight Modelling (CBDM) - a dynamic approach which goes beyond basic static calculations - to determine the daylight performance of the building spaces and how this varies throughout the year.
IES Consulting used the RadianceIES application within the VE to perform this analysis. The CBDM approach involves an annual simulation, linking location, shading and climate data, together with the building properties. The analysis considers any solar shading devices (internal or external), including any manual or automatic controls, to limit the maximum and minimum daylight entering the space. The metrics used to assess space daylight performance are Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE), which require individual simulations to be run for all regularly occupied spaces across the calendar year.
Through their analysis, the IES consultants were able demonstrate a maximum 3 points could be achieved for the LEED v4.1 Daylight credit.
To ensure the building’s high performance design intent carried through into operation, IES Consulting were also appointed as the LEED Commissioning Authority (CxA) and overall manager of the commissioning (Cx) process for the An Post Headquarters, in accordance with LEED ID+C v4 EA Fundamental Commissioning & Verification and EA Enhanced Commissioning Option 1.
IES was responsible for the composition and compilation of the commissioning plan and all other commissioning documentation requirements, as well as the functional performance testing (FPT) for energy-consuming systems included within the commissioning scope.
The commissioned systems included:
To address any issues identified during the final commissioning process, IES coordinated with various contractors to ensure the effective operation of the building systems, refining operations to meet the owner’s best interests, adjusting and/or replacing defective components, and completing all of the contractor documentation. Specific examples of issues encountered and resolved included replacing filters on the AHUs, ensuring the correct configuration of one of the A/C units which had been flagged through the BMS, and rectifying a fault with one of the extract fans.
The commissioning process is vital in ensuring a building performs in line with its design intent and any specification requirements. However, it is important that the building’s operational performance is not allowed to drift over time. While the consultants were satisfied that the commissioning process has ensured the proper installation, calibration, and training required to support the efficient running the building systems, the ongoing commissioning plan issued to the client will help to ensure that the building continues to operate efficiently over time.
