HEATING RETROFIT | RESIDENTIAL TOWER PITCH PERFECT The option to upgrade to hydrogen boilers in the future was one of the reasons a London housing association opted to install gas boilers in the retrofit of a residential block next to Charlton Athletics football stadium. Baxi Heatings Ian Lock describes how prefabrication of utility units saved time and labour on the 17-storey tower BENEFITS OF PREFABRICATION Time and labour savings, on and off site Cost savings 13.4% on average, according to CIBSE Quality control clean, controlled environment with end-of-line testing Reduced material waste reduced environmental impact Improved asset management golden thread of building Easier to prioritise health and safety reduced activity on site and fewer hot works Faster, simpler installation reduced need for onsite specialist trades Reduced risk for all stakeholders. J ust a stones throw from Charlton Athletic FCs Valley stadium is Valiant House, a 17-storey residential block run by housing association Charlton Triangle Homes (CTH), part of the Peabody Group. Ensuring the building services for the 93 flats are well maintained and monitored is the responsibility of Peabodys electrical and mechanical services department. So, when the CTH board reported signs of deterioration in 2019, the team undertook a rigorous inspection. The existing heating plant consisted of non-condensing gas boilers, located in a roof-top plantroom, that supplied heating and hot-water services to the individual properties. A few years earlier, the team had carried out improvement work to optimise boiler performance, but the current survey revealed the boilers were beginning to operate less efficiently and economically. A second issue was the gas main feeding the boilers with thinning pipe walls, this was at the end of its 50-year life and needed replacing to comply with new regulations and Health and Safety Executive (HSE) requirements. SGN, which supplies the gas to Valiant House, was also preparing to replace its pipes in the building. Achieving an efficient long-term solution for the residents while ensuring uninterrupted continued use of the building were the dual goals for CTH and Peabody, who brought in an external consultant to review the findings and present a series of options. Ground source heat pumps (GSHPs) were the first consideration, in line with CTH and Peabodys wider environmental commitments to reduce their carbon footprint. A potential obstacle, however, was the proximity of the property to The Valley stadium. Ian Winterflood, head of electrical and mechanical services at Peabody, said the housing association was keen to explore the feasibility of applying low carbon technologies, but concluded that it was not technically feasible as there wasnt enough space around the building for the underground services. Another option, to replace the gas main and pipe risers to the building, also had to be Achieving an efficient long-term solution for the residents while ensuring uninterrupted continued use of the building were the goals rejected. It would have required the removal of concrete through floors to access the existing pipework creating extra work to protect the building structure and running a gas main up the side of the building would have added scaffold costs because of the size and weight of the pipe. A third option was to move the plantroom from the rooftop and create a new centralised plantroom, capable of meeting the demand of the building, in a larger, unoccupied space at the rear of the building, on the ground floor. This proposal involved the installation of high-efficiency condensing boilers to supply new heat interface units (HIU), indirect cylinders with electric backup, and individual heat meters in each property. Included in this last option was the replacement of 42 January 2021 www.cibsejournal.com CIBSE Jan21 pp42-43 Baxi Retrofit 2.indd 42 18/12/2020 15:53