CASE STUDY | 11 BELGRAVE ROAD The retained concrete frame facing onto Belgrave Road Getting your homework checked by another consultant is a really important step with Nabers, because they go through your modelling and give you detailed feedback on the design landlords domestic hot water system via a water source heat pump. In summer, were going to get free cooling and hot-water production because all the rejected heat [from the offices] will be used to heat the domestic hot water, explains Irvine. Electric immersion heaters provide backup heat to the calorifier. Ventilation to all the office floors is from a variable air volume (VAV) system, with control based on CO2 levels. Air is provided by a central air handling unit (AHU) and local mechanical ventilation with heat recovery units. They serve different zones of the office floorplate, which is designed to be sub-divided into three tenancies. MVHR units serve two zones and the AHU serves one. To achieve WELL certification, outside air ventilation rates were increased from 10ls to 12ls per person for the offices. Design occupancy density was 1 person per 8m2. To further improve air quality for the building users, the air is cleaned using carbon filters. Openable windows are on both the Belgrave Road and Guildhouse Street faades. Openings are manually operated, with the buildings BMS and smart buildings platform advising occupiers the best time to open/close windows from an energy and air-quality perspective. Once the MEP design had progressed sufficiently to enable energy use to be modelled, Max Fordham had to submit its modelling report for independent review. In this instance, the reviewer was Delta Q in Australia. Getting your homework checked by another consultant is a really important step with Nabers, because they go through your modelling and give you detailed feedback on the design, says Irvine. One downside of adopting Nabers late in the project was that Max Fordhams energy modelling was undertaken relatively late in design development, which meant it was too late to take on board all of Delta Qs recommendations. Irvine explains: They were commenting on the architectural form of the building and the potential to add external shading, but, at RIBA Stage 4, the project was too far down the line to do anything about shading. Another recommendation that could not be implemented, but which highlights the level of detail required under Nabers, was the reviewers recommendation to refine the controls on the VAV system. This is because, in the UK, a VAV system is typically controlled to maintain a fixed pressure in the ductwork, with the VAV dampers opening and closing independently of the fan speed. To save energy, Delta Q recommended changing the controls to keep the damper in the VAV unit on the MINIMISING EMBODIED CARBON As well as minimising operational carbon, Eric Parry Architects design for the renewed building retains a significant proportion of the existing 1950s concrete structure and foundations, as part of an overall strategy to reduce the embodied carbon of the development. This has reduced the schemes embodied carbon for the refurbished areas to 2 2 324kgCO2m- , below the LETI target of 350kgCO2m- for commercial buildings, with 2 the projects overall embodied carbon emissions predicted to be 466kgCO2m- . The retained structure supports the addition of two new office floors on the roof, which are stepped back from the existing faade in order to be hidden from the road. The entire structure is enclosed by a new curtain wall. Partial reuse of the 1950s concrete frame significantly reduced embodied carbon 48 February 2023 www.cibsejournal.com