CASE STUDY | ESB HQ, DUBLIN The retrofit of the Electricity Supply Boards offices in Dublin was a test bed for innovative heating and ventilation systems. BDPs Chris Croly describes the buildings transition from gas to electric ELECTRIC AVENUE T he Electricity Supply Board (ESB) is majority owned by the Irish government, providing generation and distribution of electricity in Ireland and internationally. It has a target of being carbon neutral by 2040, and is investing heavily in renewable generation and associated technology, such as energy storage. The redevelopment of its Dublin headquarters was an opportunity to contribute to the advancement of sustainable office development. To reflect this, a passive design approach has been taken, working with the local climate to minimise heating and cooling loads. Unsurprisingly, the ESB has moved away from gas to embrace heat pumps with heat recovery, while ventilation is a combination of natural and hybrid solutions. The project contains two office buildings within one city block. The first is ESBs headquarters, which will also serve as a research tool; it is hoped that it will provide a source of intelligence on new techniques and technologies that will influence the next generation of offices. The second building includes many of the same techniques, but is optimised for the commercial market. Almost all large commercial offices are sealed, air conditioned buildings with traditional services, so it was important to create a sustainable alternative that could stand as a precedent. Dublins commercial market approved of the approach, placing a value on the building that covers the full cost of the development of both offices. The design follows first principles and focuses on minimising energy demand. The use of fully glazed facades was explicitly banned in the design competition brief because they can lead to excessive heat losses and heat gains which increase energy usage. Glazing areas were adjusted by location, with smaller areas on the more 42 August 2022 www.cibsejournal.com exposed upper floors. South- and west-facing glazing is provided with solar control, while solar gains are encouraged from the north and east. South-facing faades have vertical external shading, optimal for blocking solar gains in the afternoon. A 1.5m soffit strip of 1.5m of exposed mass is used at the perimeter in the form, raising the glazing level and projecting daylight deeper into the plan. The thermal mass absorbs heat and releases it at night. This is particularly important at the perimeter because the glazing produces some radiant heating, and the cooling effect from the concrete soffit helps to provide balance. Deeper plan areas are mainly reserved for tea stations and have open, timber grid ceilings. A 70% ground granulated blast-furnace slag (GGBS) content was used in the foundations, and 50% for the structure, resulting in a reduction of 160 kg CO2/m2 of gross floor area. Hybrid ventilation Modern offices have a net cooling requirement throughout the year. External temperatures in Ireland are almost always lower than required internal temperatures, so sealing offices and actively cooling them may not make the best use of free cooling. The insulation and low infiltration levels of sealed buildings is likely to have a negative effect on cooling. The hybrid ventilation solution used at ESB combines the best of natural and mechanical ventilation, and active cooling. In combination, better air quality is produced, with lower energy usage, than by each individual solution. In cellular spaces, an innovative technique was used that links the inlets to the fan coils directly to the open-plan space, so that large volumes of air exchange occur