Delivering the buildings of tomorrow’s standards today

CIBSE Awards, Max Fordham
The future of building design — the energy consumption of the City Academy in Hackney is 40% better than required by Part L 2006.

An insight into how buildings of the future might be designed and serviced is provided by the City Academy in Hackney, winner of the award for new-build project of the year, for which Max Fordham LLP was consulting engineer. This project was designed to perform 40% better than required by Part L of the 2006 Building Regulations, which is a further 20% better than the 25% improvement due in the 2010 Building Regulations. It has a A-rated Energy Performance Certificate and a ‘Very good’ (63.8%) BREEAM rating. It received its first students in September 2009.

Most of the energy savings have been achieved through passive design, with the building-services installations, controls and onsite renewable energy providing further reductions in energy use — at additional cost and with long payback periods.

These passive measures include optimising natural daylight and ventilation. Lighting, ventilation, acoustics and energy designs were modelled and tested to come up with the optimum solution. Classrooms have an outside aspect and also adjoin the full-height central atrium that acts as a circulation area.

Well lit is generally considered to be an average daylight fact of 4 to 5%. The City Academy achieves 7.5% on the third floor, 4.3% on the second floor and 3.9% on the first floor. Corridor atria bring light down through the heart of the building, so classrooms receive light from both sides. Light and glare is controlled by blinds.

The City Academy is close to a busy road, with high noise levels. Natural ventilation is achieved by combining a double facade with attenuated ventilation openings. Air from outside passes across classrooms into the central circulation space, where it rises to the top of the atrium and out through large ventilation openings. The opening acoustic vents in the facade can be controlled to provide background ventilation, rapid ventilation during the day and secure ventilation at night.

Underfloor heating integrated into the raised access floor provides space heating.

The submission for the City Academy identifies the energy savings and relative costs of the various low-carbon measures.

At the top of the list is natural ventilation saving 180 MWh of electricity a year compared with fans and cooling to move the same quantity of air.

The daylighting being 70% better than a poorly lit building, which would require artificial lighting continuously in working hours, reduces electricity consumption by about 85 MWh a year.

Further energy-saving measures move into the realm of long paybacks.

Demand-based mechanical ventilation using presence sensors and monitoring of CO2 levels, will save 54 MWh of electricity a year, with a 10-year payback.

Heat recovery in mechanically ventilated areas will save 50 MWh of heating a year, but with a payback of 30 years.

There are 130 photo-voltaic panels on the roof to produce 16 MWh of electricity a year, with a payback of 41 years, even with the help of a grant from the Low Carbon Buildings Programme.

The ground-source heat-pump system will use 70 MWh of electricity a year to displace 315 MWh of gas. The payback, with a grant from the Low Carbon Buildings Programme, is 95 years. It has 50 loops of pipe below the sports pitch.

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