CASE STUDY | ESB HQ, DUBLIN Timber grid ceilings are used in tea rooms and deeper plan areas (left), allowing concrete to be thermally visible units are run in parallel to minimise fan power at times of low ventilation need. Initial monitoring shows: 85% less fan energy than would be consumed in a typical office building; almost no active cooling required, even with external temperatures above 20C; excellent air quality. Heating and cooling The offices are a zero local pollution building, with no fossil fuel connections, even for cooking. The operational carbon impact of the building will approach zero as the national grid decarbonises. Initial monitoring shows that almost zero heating was required (monitored data indicates a figure less than 7 kWh.m-2) and that heat was almost entirely recovered from cooling loads such as computer rooms. While multipurpose air source heat pumps (ASHPs) allow heat recovery, there are limitations and the coordination of loads by integrated controls results in unexpected losses. So, a dedicated water-to-water shunt heat pump has been included. Heat recovery is guaranteed, without the risk of the air source system cutting in unintentionally. Similarly, the hot water heat pump is connected directly to the chilled water circuit, ensuring 100% of the load is derived from recovered heat. The conventional arrangement of coupling the hot water heat pump to the hot side can cause the ASHP to kick in unnecessarily (see article on web for further explanation). Cooling is provided using a priority cascade as follows: recovery of cooling from domestic hot water heat pumps; free cooling provided by a 4.8km closed-loop ground collector; cooling recovered from any heating demands in the building; a phase change store to transfer any remaining heat rejected from heat pumps that are providing cooling. The phase change material (PCM), which is under test in this building, changes state at 10C. .In winter, the PCM stores cooling associated with morning pre-heat for use later in the day. The fan coils use a single coil with a six-port changeover valve, reducing capital costs, fan energy and embodied energy. A glycolfree system lowers chemical use while improving the heat-transfer properties of the water used. Monitoring and reporting The ESB offices are fitted with an extensive metering package, and BDP is undertaking tuning and monitoring of the building as part of a research project. Full details of the methods used in the building, along with data and the resulting insights, will be published. If monitoring shows big savings in energy and costs, others may be encouraged to go electric by switching from gas to sustainable alternatives. ESBs Dublin office stands as proof that heating and ventilation needs can be met while heading towards net zero. CJ C HRIS CROLY is the building services engineering director at BDP WINDOW ARRANGEMENT The building is set around a series of planted courtyards, with all office areas having access to external spaces, natural light and ventilation. Setting courtyards back from the street allows for natural ventilation, with less traffic noise and improved air quality. Lower-level manual openings are provided for staff, with motorised openings at high level, reducing draughts and maximising airflow. The automated windows adjust appropriately to weather, cracking open when cold, opening fully when warm, and providing night cooling, They can, however, be manually overridden by staff. Cracking the windows open whenever there is a net cooling load allows for an airtight building in cold weather without compromising free cooling in warmer weather. An often ignored constraint of opening windows is that, in warm weather, blinds are pulled over the openings to prevent glare, blocking the free flow of air. To prevent this, solid window sections were used, and openings are protected by external shading in the form of vertical fins that do not restrict airflow. 44 August 2022 www.cibsejournal.com The ESB HQ is also one big research tool for sustainable offices