Mildmay Community Centre (formerly Mayville)

More information about the Mildmay project can be found here.

 

Mildmay Community Centre exterior
 

Project lead
Nick Newman, Bere Architects

Building type, sector and stage
Non-domestic refurbishment, other non-dwelling, handover, post-construction, in-use monitoring, London.
  
Keywords
Passivhaus, MVHR, refurbishment, airtightness, external insulation, GHSP, PV

Summary
Built in the 1890s as a generating station for London's tram network, the massively constructed building was rescued from dereliction in 1973 by the Mildmay Community Partnership and turned into a community centre for the local Mayville Estate. The three-storey concrete-framed building (basement, ground and first floors) has a 600 mm-thick solid brick skin, pitched roof and a later single-storey extension. In 2006, Bere Architects was asked to refurbish and extend the rundown building.
Refurbishment works to the building include internal space re-planning to create an extra 35 per cent usable space for both local community use and renting to fledgling local businesses. Bere Architects reasoned that more space could be generated through efficient internal re-planning and energy efficiency improved massively by adoption of Passivhaus design principles. The building's accessibility was improved and a full upgrade of the fabric and its environmental systems was planned to meet the Passivhaus standard. The construction budget was £1.6 million.
As part of the refurbishment works, the external walls were damp-proofed down to the footings. External insulation has been carried down to the foundations, with 75 mm of high performance phenolic insulation added to basement concrete raft. All windows were replaced with high quality, German triple-glazed windows with detailing that avoids thermal bridging. Careful attention was paid to both the detailing and the quality of insulation.
Islington provided 50 per cent funding for 116 m2 of grid-connected photovoltaics rated at 18 kWp. The building has limited need for hot water, so the solar thermal system is a modest single 3 kW panel connected to a 300 litre tank. 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. While grateful for the funding for mechanical ventilation with heat recovery, it was dependent upon the building having an 8.4 kW Viessmann ground-source heat pump.
The existing building was consuming 581 kWh/m2 per annum (delivered energy). Using the Passivhaus Planning Package, it was calculated that fabric improvements will reduce the primary energy demand to 116 kWh/m2 per annum.
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 an 11 kW heating load for the building over a continuous 24 h period.
Using SBEM, the target emissions rate was calculated at 18.8 kgCO2/m2 per annum, with the as-designed building emissions rate set at 13.7 kgCO2/m2 per annum, an 87.5 per cent improvement on the old building.
The building was handed over in late 2011, with fit out of some spaces occurring later. Occupation of the tenanted areas has been progressive, with the basement area likely to be fitted out and occupied in late summer 2012. For this reason the early energy data will be unrepresentative of the building's longer term performance.

The walls above ground level were treated with 300 mm of expanded polystyrene block fixed to the external face of the brickwork and finished with a protective hardwearing Permarock render. Below ground the basement walls are externally insulated with 200 mm of extruded polystyrene insulation.

With so much riding on the insulation, installation quality had to be very high. A random test of recently installed blocks found that the labourers were not gluing the expanded polystyrene to the building properly, thereby creating gaps and a thermal bypass between the walls and the insulation. The main contractor's site manager ensured that the entire south elevation was dismounted and properly re-attached to the building.

Mildmay community centre scaffolding on walls

The construction quality of the eaves junctions needed special attention, and a site inspection found that a wedge of insulation had been omitted by the insulation contractor. This left a cavity, (shown) so the contractor drilled holes at 150 mm centres and sprayed in foam insulation to make the insulation continuous and close the cold bridge.

Mildmay community centre eaves

Calflex and Rolaflex seals and tapes were used around windows to achieve the required airtightness. This is not common practice in the UK. Not only is there a time and cost aspect to their use, the tapes can only be used at certain times of the year. The builder sometimes had to work at -40C, and couldn't get the self-adhesive tape to stick. The builder had to stop work until the weather changed, which caused delays.

On the plus side the site trades got a lot of encouragement when they got things right. There was a good feeling when people left site that they had learned a lot, and that they have reached a superior standard of workmanship that they can take onto other projects.

Mildmay community centre window seals and tapes

The lighting is now manual on and auto and manual off.  However, the multi-function light switches (the iLight standard offering) have been still been installed, even though a standard on/off switch would have sufficed. This means that most of the buttons are not connected, which creates confusion and reduces usability.

Mildmay community centre lighting control

Bere Architects has created some simple information panels to explain to the tenants how the various systems work, in this case the blinds and the rocker switches that operate them:

Mildmay community centre blinds control diagram

Early outcomes
Performance measurement has been hampered by a sub-metering installation that has not delivered meaningful data on energy consumption. Inaccuracies in the meters, plus an inability to correctly account for the contribution from the PV and the amount exported to the grid (which also adversely affected the sub-meter readings) has led to the installation of temporary metering.
The (largely) fluorescent lighting for the ground floor offices and first floor meeting rooms is controlled by an iLight controls system. The lighting (lux) levels were intended to be easily modified according to users' preferences. However, iLight use a closed communications protocol devised in-house called ICAN. This means only someone with the right software interface can access the system and make changes.
With closed protocols there is also a major risk of obsolescence that could lead to technical support stopping sooner than the next refurbishment. Open communications protocols are much less riskier for that reason, but companies prefer to develop their own software.
As part of the cost reduction exercise some of the proposed dimmable lights were replaced by non-dimmable fixtures in office spaces. This affected the commissioning of the lights and the way the occupants are using the controls, as the light switches (remote dimmers with five programmable lighting scenes) installed are designed for dimmable lighting.