VENTILATION 2 M&E CASE STUDY


Projected energy usage and overall savings from renewable technologies and natural ventilation, based upon the design modelling


Ground-source heat pump (150 kW)


Projected energy saved per year (kWh)


Projected energy generated per year (kWh)


Projected carbon reduction


Projected cut in carbon emissions (kg CO2


) PROJECT TEAM


Project: Child and Adolescent Mental Health Services Unit, Colchester


client: North Essex Partnership NHS Foundation Trust


M&e design: Atkins Architect: KLH Architects


Qs And Project MAnAger: Castons


MAin contrActor: ISG Jackson


totAl cost: £9.6m (inc all fees) M&e cost: £2m approx


*Base = design projections showing the building before any zero and low carbon techniques have been applied, and assumes comfort cooling for some areas. **There is a projected increase in electricity consumption but overall there is a net decrease in carbon emissions with the technology applied. ***The reduction in carbon emissions is compared against having comfort cooling to the treatment and consultation rooms, gym area, bedrooms, offices, dining areas and reception areas.


where the architect has worked with Andrew Stevenson, lead mechanical design engineer at Atkins, to embrace the natural ventilation scheme within the overall building design. Atkins worked with Monodraught to


overcome the problems of air movement that extending the height of the Windcatchers inevitably brought. ‘Raising the height does alter the air flow rates, noise, aesthetics and the cost, so we’ve sat down as a team to come up with the best solution,’ says Bourne. Each of the units in the main corridor and circulation areas is predicted to provide a ventilation rate of 420 l/s at an external wind speed of 3m/s. According to the design


modelling used, there is a projected saving in carbon emissions of 40,000 tonnes a year from using this ventilation strategy, compared with air conditioning in the treatment and consultation rooms, gym area, bedrooms, offices, dining areas and reception areas. A 150 kW ground-source heat pump


supplies the low temperature hot water for the building’s heating and 30 sq m of solar thermal collectors provide the pre-heat for the hot water requirements. High efficiency gas condensing boilers act as a back-up for the heat pump. ‘This may seem a bit belt and braces,’


says Bourne, ‘but the client wanted resilience. This is a 24-hour building and will operate at 75 to 80% of maximum occupancy at all times.’ There are also about 112 sq m of solar


photovoltaic panels generating 15 kW of electricity that will be eligible for payments under the government’s feed-in tariff scheme. This will be used to charge up


60 CIBSE Journal May 2011


a battery-powered lift and also to drive fans in those areas that need mechanical ventilation. ‘We’ve opted for what we call sensible


sustainability on this project,’ says Bourne. ‘We’ve added to the saleability of the space there and added credibility to the Trust’s corporate social responsibility agenda by providing a green, low-energy building.’ The team has avoided any measures that


We aim to ensure that any possible building changes required also include M&E services


were considered either too costly or that may have encountered planning problems, such as combined heat and power. Early designs also considered the incorporation of a wind turbine, but the payback period proved to be too long. In any case, the area is surrounded by trees that are protected


by tree preservation orders, something that dictated the building’s footprint and also limited the space for plant and services distribution routes. On the electrical side of the project,


the team has opted for low energy T5 fluorescent lighting internally. All lamps are daylight linked, coupled with both absence and presence detection to further save energy. Externally, LED lighting was chosen for its low maintenance and improved energy performance, despite the higher capital cost over conventional solutions. The project demanded a new 280 kVA substation on site. The turf has been cut and the project


has moved into the construction stage. ‘The project was tendered as a traditional single-stage tender package,’ says Bourne. ‘This helps to ensure that the building is constructed in a well co-ordinated way and any possible building changes required also incorporate the M&E services.’


www.cibsejournal.com 6.8% 11,464 3.3% 5,457 14,352 kWh (Gas)**


Solar Thermal Photovoltaics (15 kW)


12,255 kWh (Gas)***


14,765 kWh (Elec)


5.0% 8,378 20% 40,286** 35.1% 65,585 Natural ventilation


Total reduction from base*


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