16 C O N T E X T 1 5 9 : M A Y 2 0 1 9 vaulted jack arches throughout. The Main Mill has a grid of cast-iron columns at near-regular three-metre spacings. With no opportunity to introduce raised access floors or a ceiling distribution zone, this means that all services will be exposed to view. Structural The original cast-iron frame is delicate by modern standards and the struc- tural strategy for the scheme has placed a number of limitations on the services strategy. For example, the use of gas is forbidden within the open-plan structure of the Main Mill in order to eliminate any explosion risk that may compromise the structure in an emergency. In addition, there is a limitation on the size of penetrations that are permitted through the main service risers in the building. Historic The listed nature of the buildings introduces a number of limitations, particularly in relation to penetrations through the facades for ventilation systems. Coupled with the limita- tions on penetration sizes in risers, this has led to a strategy of local ventilation systems with carefully placed exhaust louvres to minimise the visual impact on primary elevations. Phasing The phased nature of the project has introduced several constraints, especially given the unknown future uses of other buildings around the site. Proposed strategy The buildings will be heated using natural gas. This is contrary to the original master plan aspiration, which was for a distributed district heating system using both biomass and gas CHP engines. However, once it became apparent that the development would be phased over a num- ber of years and the economics of the district heating system were appraised, it became clear that the focus should be on local heating sys- tems on a building-by-building basis. The main heating plant will be situated in the former engine house at the south end of the building, which is structurally robust enough to permit the use of gas appliances. Efficient condensing boilers have been specified and pipework will be distributed at skirting level throughout the main mill, serving floor-standing gilled tube radiators. Ventilation will be primarily natural using opening windows, with local extract systems to WCs designed within the structural constraints described earlier. The cafe’s kitchen ventilation plant will be hidden from view within a mez- zanine plant area and the exhaust will rise to roof level. A basement undercroft below the south engine house will be used to incorporate a mains water storage tank and booster set, to provide adequate pressure toWCs on the upper levels. The main incoming power supply will come from a new substation in the proposed car park to a switchroom located in the heart of the kiln. A network of sub-main panels and distribution boards will allow all areas to be separately wired and metered.Within the Main Mill floors, perimeter trunking will be installed to provide wiring routes for tenants to fit out the floor plates. A strategy of floor-mounted lighting is proposed to provide flexibility for a multitude of fit-out scenarios without introducing a grid of suspended luminaires that may compromise partition locations. A plan of the site (Image: FCBS) Hugh Griffiths, a partner at E3 Consulting Engineers, has been the lead mechanical design engineer at Ditherington Flaxmill since 2009.