Bere Architects’ retrofit stretched its tiny budget, winning funding for being the first non-domestic London Passivhaus
More from: Passivhaus leaves home
Originally a generating station for London’s tram network when built in the 1890s, the almost derelict building was converted into a community centre for the Mayville Estate which surrounds it in the 1970s. Bere Architects reconfigured the space by excavating the south side to provide light (and solar gain) to the basement, and added a single-storey entrance pavilion which houses a reception and a future café.
All windows are triple-glazed units manufactured in Germany, fitted with external retractable Venetian blinds where appropriate. Footings were excavated to the
slab and insulated with 200mm polystyrene insulation - sealed with tape - over a parge coat. Above ground, 300mm of expanded polystyrene block was glued to the external brickwork and finished with external render. A new zinc roof with 400mm of insulation sits over existing steel trusses. Renewables include PVs and solar thermal, made possible through grant funding. Building performance is being monitored by the Technology Strategy Board.
AJ Buildings Library
Q + A Justin Bere, director, Bere Architects
Why did you decide to go for Passivhaus?
Initially I was asked to look at the building to advise on putting in a biomass plant, but we started instead by looking at how to save energy. The basement was dark and unused, so we suggested excavating and adding south-facing windows, which would bring light in and generate heat for the building. There was no budget so it wasn’t a matter of ‘we can’t afford that’. There was no money, full stop.
Did Passivhaus restrict your design options?
No. It shows you that if you waste energy in one place, you need to compensate for it somewhere else. You could put big windows on the north side but then you would have to add more insulation to the envelope.
I don’t think we would have received permission from Homes for Islington to excavate and add all the windows overlooking the south garden if we hadn’t been able to use Passive House Planning Package to demonstrate the long-term energy and comfort benefits.
This is London’s first non-domestic Passivhaus, and all the funders liked that. We received about £260,000 from the council for renewables and the 90 per cent heat-recovery ventilation. The Carbon Trust, the Big Lottery Fund and the Community Builders Fund were also among those that helped fund the project.
Is the building more complicated to use and look after?
It’s much simpler than a normal building. Typically a building this size would have a building management system, but we decided to keep controls really simple. Our controls are no more complicated than a domestic thermostat. A ground-source heat pump supplies any heat needed to the radiators, which have simple thermostatic valves.
All lights are manually switched on and off. Presence detectors are used to switch lights off if they are forgotten. External retractable blinds (and insulation) help keep the building cool in the summer, and are adjustable so we get the light in but not the heat. These are very easy to operate.
What were the biggest successes of the project?
The redeveloped centre has helped lift the surrounding area; its white and grey render transforms the estate; its gardens are now actively used by the community. Users of all ages are excited by how their building is heated mostly by the sun.
The airtightness at 0.43ach-1 at 50Pa was a triumph on any project - especially a retrofit - and provides QA on the fabric, allowing the services to be sized and operated in accordance with the design model. This is an all-electric building and by fabric-first measures and sensible controls, I think we will keep electrical and primary energy consumption so low that the PV will provide about half the energy requirements of the building.
Running costs will be about £800 a year compared to £10,000 before (with no feed-in tariff). The building uses 90 per cent less energy than it did before, with less than 10 per cent of the running costs, and it’s really warm in winter and cool in summer.
Passivhaus community centre: Mayville by Bere Architects