SPECIAL FEATURE


The community centre hall nearing


completion.


multiple work stage drawings for complicated junctions. Two airtightness tests were carried out, the final test showing a value of 0.43 – remarkable for a 19th Century building.


BUILDING SERVICES


The design team wanted to reduce energy consumption to the minimum, but as always there is a balance to be struck between highly carbon-efficient technologies, their capital cost, and the ease by which they can be subsequently managed and maintained in a building without on-site premises management. Energy consumption (including unregulated loads) was modelled using the Passivhaus Planning Package (PHPP), a spreadsheet-based design tool for those designing to Passivhaus standard. The PHPP predicted a 7 kW heating load for the building over a continuous 24 hour period.


There was no money in the tight budget for mechanical ventilation with heat recovery (mvhr) – a fundamental element of the Passivhaus approach – but the architects successfully argued for heat recovery ventilation to be part-funded from the £3 million Islington Climate


Change Fund. This was originally intended only to fund heat pumps and photovoltaics.


The variable volume


Paul Maxi mvhr unit is sized to deliver 5.6 litres/s per person, at a specific fan power of 1.86 W/l.s for each of the supply and extract fans. Heat recovery is via a corrugated plastics heat exchanger, said to deliver close to 90 per cent heat reclaim. The fan motor is in the airstream, which provides more heat. In summer the building will be naturally ventilated through openable windows. The entire building will be mechanically ventilated in winter, with volumes based on carbon dioxide readings. The perimeter offices only have a supply, their extract being out to the hall.


In normal day-to-day use the hall will not need its own ventilation. At times of high occupancy, a carbon dioxide sensor in the return air ductwork will open up a ductwork damper to supply air directly to the hall. The small cafe area will also


The Mayville


Community Centre prior to the refurbishment: leaky, energy hungry, and run- down - but still playing a vital role for the local community


have boost ventilation.


A simple timer will bring on the ventilation to provide a base load to the offices, basement and extract from toilets, while other areas will come on with demand. The wet heating system will be used for early morning warm-up to avoid wasteful use of fan energy.


While grateful for the mvhr funding, the quid pro quo was a 8.4 kW Viessmann ground-source heat pump when the services designer, Alan Clarke, would have preferred a simple gas boiler. “We had to excavate three metres of soil for the ground-source brine pipework,” he said. “It’s a bit crazy to


PUBLIC SECTOR SUSTAINABILITY • VOLUME 2 ISSUE 1 19


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