CASE STUDY | CAMBRIDGE CENTRAL MOSQUE PROJECT TEAM Client: Cambridge Mosque Trust Architect: Marks Barfield Architects Main contractor: Gilbert-Ash Structural engineer: Price & Myers Services engineer: Skelly & Couch Building services contractor: Munro Building Services Cost consultant: Faithful+Gould Landscape architect: Emma Clark Consultancy Project manager and planning consultant: Bidwells Section view of the mosque 1 High levels of insulation and airtightness 2 Rooflights reduce the need for artificial lighting 3 Entrance foyer maximises passive solar gain from low sun in winter 4 Solar shading 5 Partial green roof reduces solar heat and reduces rainwater run-off 6 Sedum roof cools air next to mechanical ventilation inlet 7 Gardens provide shade and cleanse air before it enters the building 8 Foyer fountain provides evaporative cooling on hot days 9 Demand-driven CO2 ventilation, thermostatic heating control and occupant lighting control 10Ventilation units reclaim heat from outgoing air 11 Underfloor heating 12Energy efficient lighting with controls that ensure they will be turned off or dimmed when not required 13 Thermally massive ground floor slab provides some passive cooling 14 Impulse fan in basement assists natural ventilation in basement during periods of low air quality 15Greywater recycling: waste water from ablutions areas is used for landscape and toiletflushing A Energy efficient plant (acoustically attenuated) B Heat pump to prove to the funders that our natural ventilation solution would work, says Maidment. We did a lot of CFD modelling, which showed that it could get quite hot but that there would be quite a lot of air moving over the congregation, which would keep them comfortable; and the more people present in the prayer hall, the higher the volume of air drawn through. Fresh air is drawn into all of the mosques principal spaces at low level through large, square grilles (both inside and out) featuring an Islam-inspired design. The grilles are set into the walls, and in the prayer hall, where up to 1,000 worshippers can be present, grilles have been incorporated into all four of its walls. We had no involvement with the pattern, but we did insist that the grilles had a least 50% free-area to ensure a low air resistance, says Maidment. The most challenging aspect of designing the ventilation system for the mosque is its variable occupancy. To develop an appropriate design solution, we had to understand how the mosque would be used, Maidment explains. The thing that struck me most was its very sporadic use pattern: the building is pretty much empty now [at 3pm on a Friday] but, two hours ago, there would have been around 1,000 people in the prayer hall, which means an additional heat load of up to 100kW; at other prayer times there may only be around 50 people. To accommodate these extreme occupancy variations, each air intake incorporates a motorised damper to control the volume of air entering the building. Rooms incorporate both temperature and CO2 sensors. The primary control is temperature; weve dropped the set point to 18oC so that when the occupancy level starts to rise the dampers open up pretty quickly, which means that CO2 levels never get very high, says Maidment. The air intakes also incorporate an acoustic louvre. In part, this stops external noise entering the place of worship, but it also helps prevent noise break-out disturbing the mosques neighbours. Unusually, some of the intake vents also incorporate smoke dampers. This is because the footprint of the mosque occupies almost the entire site, so the external fire escape routes to allow worshippers exiting from the rear of the building to make their way to the street in front, pass several intake grilles. The smoke dampers close to prevent smoke escaping from the building and clouding the fire escape route. Warmed air rises up and out of the building through louvres PRAYER HALL A UNDERGROUND CAR PARK 26 August 2019 www.cibsejournal.com CIBSE Aug19 pp24-28 Cambridge mosque.indd 26 19/07/2019 15:02