SCHOOLS & EDUCATION FACILITIES SUPPLEMENT NEW-BUILD ACADEMY


Natural ventilation through operable windows during spring and autumn


Raised floor for pipework distribution + power/ICT cable management


Fan-assisted ventilation in summer and winter


High-performance louvre glazing


Exposed concrete soffit for ‘passive’ cooling Multi-service raft for lighting and acoustics


Traditional, perimeter heating


Power/ICT distribution via raised floor


Figure 1: The academy has a mixed-mode ventilation system and an advanced environmental control strategy that integrates passive design with technologies


Centralised air handling unit


natural ventilation strategies alone to generate the desired comfort conditions. Instead, Fulcrum says it developed a mixed- mode ventilation system and an advanced environmental control strategy that integrates passive design with innovative technology (see box and Figure 1). The building was subject to the Royal


Borough’s planning requirement for 10% of the energy demand to be met by renewable means. Once again, the site threw up its challenges. ‘Being in the shadow of Lots Road power station effectively ruled out solar photovoltaics,’ explains Muhsinovic. ‘Also, as you would expect, the school is in the middle of a residential area, so biomass boilers were ruled out as regular deliveries of woodchips would have been a nuisance.’ The team turned to ground coupling


technologies, something that Fulcrum has used many times before in a variety of projects. Two 100-metre-deep, open-loop boreholes have been sunk to create an aquifer for use as a thermal energy store to deliver the 10% carbon reduction required by planning – Figure 2 shows the generic principles. The boreholes had to be carefully sited.


Chelsea Academy was one of the first inner-


city schools to be tasked with meeting both the acoustic standards of the Department for Education’s Building Bulletin 93 and the ventilation criteria of Building Bulletin 101. With the railway line and heliport nearby, there was little prospect of relying on conventional


Not only were there school basements to consider, but also massive liquid-cooled HV cabling from the power station and a flood- relief sewer in one corner of the site. Access to the aquifer also gave an


opportunity for the ground water to be used for irrigation, minimising reliance on utilities and reducing running costs. This was advantageous as the constrained site prevented rainwater recycling. ‘It’s an interesting way to include


Ventilation Keeping cool with night-time ‘purging’


Mott Macdonald Fulcrum has devised a mixed- mode ventilation system that combines a simple, centralised mechanical air supply and passive natural venting via opening windows to provide fresh air to all internal spaces beyond the minimum standards of BB101 (see Figure 1). Fresh air from the mechanical system supplies a minimum of five litres/s/person in addition to the openable windows. ‘With a tight building and


high levels of heat recovery for energy efficiency, you then could have an issue


16 CIBSE Journal March 2012


with overheating in summer,’ says Saud Muhsinovic, project director with Mott MacDonald Fulcrum. ‘So we added in controlled night- time purging to cool down the exposed thermal mass in the floors and ceilings and bring down temperatures.’ The design’s maximum


summer temperature is set at 28C. The building management system will monitor internal temperatures and activate night-time purging via opening toplights as required. The secure night- time purging introduces three


litres/s into the classrooms. Should the night-time


ventilation not be sufficient to bring temperatures down to the desired comfort conditions, the aquifer thermal energy store (see main text) can be used to bring more coolth into the building. The mechanical ventilation


supply comes into the classrooms from a passive wall grille via corridor ductwork; the grille has an attenuator on the back to ensure acoustic separation. The corridor acts as the return air plenum.


renewables,’ says Muhsinovic. ‘It’s not the cheapest option, but it’s the right technical solution for this particular project. There are issues with extraction licences, the boreholes can silt up, and even with all the data and research, you don’t know exactly what you are going to find until you drill. But more and more large-scale projects are looking at open- loop boreholes, because significant carbon savings can be achieved as you can do away with large chillers.’ The aquifer thermal energy store is easily


linked to the mechanical ventilation system to give the ability for both cooling in summer and heating in winter. The night-time purging can be used in conjunction with the store in summer, for example, to bring down peak temperatures, so the solution brings comfort benefits as well as energy efficiency improvements. This could well prove beneficial in the future, as heat loads from IT equipment are


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