CASE STUDY | GOOGLE KINGS CROSS OFFICE The chilled water system is described by Maruthayanar as variable speed. From the chillers, we have a pump set circulating chilled water around the AHU circuit; a pump set that supplies the perimeter trench units on the office floors; and a pump set serving the ground-level spaces. Dividing the system into three allows the pumps to turn off if there is no load on a particular circuit. Heat for the AHU coils (and domestic hot water) is supplied from the combined heat and power (CHP) and boiler plant forming the Kings Cross district energy centre. Although Kings Cross Energy Centre generates heating and cooling, it could only supply heat to this building, which is why we have the chillers, Maruthayanar says. The AHUs are fitted with carbon filters and F9 filters to maximise indoor air quality. This is an enhancement on what is the norm for London office buildings, Maruthayanar says. The filtered, tempered fresh air is ducted to the floor plates via risers formed in the buildings five concrete cores. Prefabrication halved the construction time of plantrooms The benefits of BIM BIM was a project requirement. Modelling was key to coordinating the mass of services within the floor voids, a task made more challenging because the voids incorporate a structural grid of castellated up-stand beams, on the concrete and CLT floors, through which many of the services had to pass. The best way we could see to coordinate everything was to use the BIM model to position the openings in every up-stand beam, to ensure the services could pass through the castellations, Maruthayanar says. There are more than 10,000 such openings. It was quite an intense information process, she recalls. BIM also enabled early specialist contractor involvement, which was helpful Early involvement of specialist contractors ensured access for plant maintenance was incorporated into the model at an early stage in finalising the MEP base-build design. The trade contractors took our RIBA 4A level design and evolved it to a RIBA 4B design with greater specificity over fabrication and installation, which we then adopted back into our BIM model, Maruthayanar explains. Early involvement of the specialist contractors ensured appropriate access for plant maintenance was incorporated into the model at an early stage, along with MEP secondary steelwork and support systems. Maruthayanar says: Involvement of the trade contractors enabled us to provide detailed RIBA Stage 4B drawings, which were a step beyond the standard for MEP projects. This helped reduce the construction programme and smooth the installation process on site. BIM also enabled extensive use of MEP prefabrication in the basement plantrooms and risers. We had allowed zones for the installation of prefabricated service modules within the risers, but we had not developed the structural support system for the modules, say Maruthayanar. When the 4B process occurred, the trade contractor responsible for the multi-service modules was able to add all the supporting steelwork, gantries and walkways to the model. As well as being able to spatially coordinate the secondary steelwork, its addition to the BIM model enabled the weight of the prefabricated modules to be established, which was useful in helping finalise the structural model. Prefabrication was beneficial, as it meant the modules were worked on off site by various trades simultaneously, which helped speed construction on site, says Maruthayanar. Needless to say, the building will be smart. Maruthayanar says Google will be developing its own network infrastructure to integrate the engineering systems and give users with tools to improve productivity and create a platform of accessible information, to make the building more flexible. The giant building is aiming for Breeam Outstanding and Leed Gold certification. According to Maruthayanar, the impact of Atelier Tens passive, active and renewable measures is calculated to achieve an overall reduction in CO2 emissions of 22% against Part L 2013 target emissions. CJ If you can find a more efficient and cost-effective HIU on the market... SPECIFY IT! MTA Plus heat pump-ready Heat Interface Unit Registering the lowest return temperatures of any BESA tested HIU, the MTA Plus is perfect for use in 4th generation heat networks. Combined with impressive outputs and a low maintenance design, no other units come close! The future of heat networks is here. Find out more: www.modutherm.co.uk +44 (0) 345 521 5666 48 March 2023 www.cibsejournal.com