CASE STUDY | CAMBRIDGE CENTRAL MOSQUE A DOSE OF WISDOM Skelly & Couch opted to use a low-level dose of chlorine dioxide as a disinfectant for the hot water supply. While we are heating the water to 55oC to kill off any legionella, the dosing system is there as a back up just in case, on an exceptionally cold day, the air source heat pumps dont quite get to the required temperature, says Mark Maidment. He says no special pipework was required for the system. All the domestic water systems in the mosque are installed using Pex pipe. This was selected on the advice of the building services contractor Munro, after it had raised concerns that, if copper pipes were used, they would be likely to pinhole as a result of the water quality in Cambridge. One of the ablutions spaces for worshippers Plant room 1 Low-loss header 2 Incoming primary heating and cooling pipework 3 Three 1,500L thermal stores 4 Primary heating pumps 5 Pressurisation unit 6 Primary cooling pumps 7 Rainwater harvesting tank leaf filter 8 Rainwater harvesting tank (10,000L) 9 Mechanical control panel 10Chlorine dioxide treatment unit 11 Cold water storage tank (1,700L) 12Cooling plate heat exchanger 13Secondary cooling pump 14Tertiary heating pumps The entrance lobby with the canopy beyond to heat the building anyway. In summer its not so efficient, but then wed still have to heat up a large quantity of domestic hot water in any case, he adds. The water supply is treated by dosing with chlorine dioxide (see box A dose of wisdom). Its quite an unusual solution, but it means that we dont have to elevate the water temperature from the heat pumps above 55oC [to prevent legionella], says Maidment. The water is perfectly fine to drink, and it means that because there is a lot of sprayed water in the ablution areas there are no concerns about legionella, he adds. The large quantity of hot water is required for ritual washing before prayer, and the mosques toilets feature extensive ablution spaces for worshippers. The facilities include ablutionary showers or douches on a flexible hose. These require adequate backflow protection, because the regulations say that the shower head could be dropped into contaminated water in the WC pan, for example, at the same time as the water pressure in the shower supply drops, which could cause water to travel up the pipework. The Water Fittings Regulations classify the risk of backflow from fluids in contact with ablutionary showers as Fluid Category 5 the highest risk level because of the potential presence of faecal matter and other bodily fluids. Maidment says that, in response to the regulations for Category 5 installations, the design incorporates an independent supply pipe from a separate pumped system to ensure backflow does not occur. To minimise water consumption, toilets are flushed and the gardens irrigated using rainwater harvested from the roof. The roof also houses a photovoltaic (PV) installation to meet the planning requirement for 10% of the buildings energy to come from renewable sources. Its a big roof, and with our all-electric solution, the PV installation made perfect sense, says Maidment. The mosques variable occupancy patterns are making it challenging to commission the building services. During Ramadan, the mosque was full every day so we were able to take advantage of this to make quite a lot of adjustments to optimise the systems performance, says Maidment. He says the mosque is currently using more energy than predicted but, because everything is monitored and metered over time, its performance will be optimised. It is fitting that the building should live up to its billing as an eco-mosque. As Tim Winter, chairman of the Cambridge Mosque Trust, has noted: Islamic civilisation has been based on the rejection of waste as an underestimation of Gods blessing so, in the construction of the new mosque here in Cambridge, we were very much in the forefront of the local environmental movement. CJ 28 August 2019 www.cibsejournal.com CIBSE Aug19 pp24-28 Cambridge mosque.indd 28 19/07/2019 15:02