Dublin city housing regeneration to passive-grade & community hub

Description

Context

Before the refurbishment started, the local authority had around 1,500 bedsits right across the city. Known as zero-bed units, they were small – usually no more than 26 square metres – and as they aged, they became progressively less attractive to tenants. Moreover, the more unattractive the location, the more ‘de-tenanted’ they became. So began a vicious cycle of vacancy, dilapidation and social deterioration.

Issues tackled

Back in 2008, before the current housing crisis had taken hold, a decision was taken to suspend the refurbishment of bedsits and instead begin amalgamating them into larger one-bedroom units. Fast forward to 2014, and as the housing lists lengthened, the policy of not re-letting these units was rescinded. Instead, city councillors decided to reintroduce these bedsits to the housing stock and refurbish and re-let them according to demand.

It was also agreed that the city council would proceed with a more limited programme of amalgamations. To date this has focused in general on elderly residents, since it is this demographic that tends to live in bedsits. While providing tenants with more space was the key driver of the programme, it would never be enough simply to knock bedsits together and leave it at that. Low energy retrofitting would form a central part of the process.

Actors involved

• City of Dublin
• EU Horizon 2020 programme
• Passive House Academy
• Design & Kelliher Miller Architects
• Morley Walsh & Associates (mechanical engenieering)
• Greenbuild (Airtightness tester)

Actions carried out

• Passive-house standard retrofit
• Creation of a community Hub
• Training for the whole team on insulation works
• Post occupancy monitoring

Results

In all, 22 bedsit apartments were amalgamated into eleven one-bed apartments as part of this phase of the project, undergoing a passive retrofit in the process. In addition, the community centre which forms part of the complex was also renovated to a very high standard.

During the refurbishment Enerphit was used, the passive house refurbishment standard which perfectly fit into the aim of helping elderly tenants particularly vulnerable to fuel poverty. Costs are low, maintenance is low and there are the health benefits associated with living draft-free in clean air. The project was certified by MosArt on 1 May 2019, with a space heating demand of 21 kWh per square metre per year, comfortably below the threshold of 25.

The newly upgraded apartments have vastly improved thermal performance – up to 80% better than the previous units – and are fully compliant with the current building regulations. Because the apartments will remain in the ownership of the council in the years ahead, one eye is kept on long-term maintenance issues.

Each of the St Bricin’s Park apartments is equipped with a Nilan Compact P exhaust air heat pump, which provides space and water heating, and ventilation. Insulation is accessible and replaceable (some of them have to be replaced every fifteen years).

The actions were finished in 2019 with a budget of €1.7million.

The project was also part-funded by SEAI’s deep retrofit programme, part of which includes post occupancy monitoring.

Why it works

In addition to a healthy, low cost, low maintenance living space, the development also delivered a community hub which has already begun to breathe new life back into the area.

Besides that the other innovative feature of this project is how the construction and design teams engaged with passive principles onsite. For a start, the council made it a requirement that the contractor undergo passive house training. A space was prepared in the canteen of the community centre where the training was given. Everyone on the contractor’s side were included and also a substantial number of council personnel were brought to do demonstrations to learn about airtightness and external insulation. The training materials were developed as part of an EU Horizon 2020 project called ‘Fit-to-NZEB’.

Nevertheless, achieving passive standard airtightness in a retrofit is always a challenge. A combination of Blowerproof paint-on airtightness sealant applied at junctions of floors and walls, Siga membranes and tapes at ceiling, and tapes to external windows and doors achieved an average standard of 0.55 air changes per hour (better than the passive house standard of 0.6, never mind the Enerphit standard of 1.0). Achieving these levels of airtightness, especially on retrofit is a result of an excellent teamwork.

In terms of external insulation, it was deployed to achieve the requisite U-values on the walls and to eliminate thermal bridges. To the same end, a large concrete eave to the front of the building had to be cut away and the new eave wrapped in insulation. Ceiling heights were very restricted and existing walls also caused problems, so the Council had to work with confined spaces while at the same time trying to keep duct lengths as short as possible.

While the council has already invested resources in acclimatising the tenants to their new homes, it was decided to meet with them again in a group once they are settled, in order to address any issues and ensure that everyone understands how everything works.

Scale

local

More information

Building type: 22 x 1960s bedsits (approx. 26 sqm each) turned into 11 one-bedroom (approx 60 sqm each) apartments & a community centre. Concrete block/brick structure with pitched roof & concrete tiles.

Location: St Bricin’s Park, Block 2, Arbour Hill, Dublin 7

Budget: €1.7m

Passive house certification: Enerphit certified

Note figures below are averages for the 11 units

BER

Before: E2 (359 kWh/m2/yr) After: A3 (63.8 kWh/m2/yr)

Space heating demand (PHPP, after): 22 kWh/m2/yr

Heat load (PHPP, after): 11 W/m2

Primary energy demand (PHPP, after): 127 kWh/m2/yr

Heat loss form factor (PHPP): 2.9

Overheating (PHPP): 0%

Energy costs: €54/yr calculated annual space heating costs & €203 annual calculated domestic hot water costs, based on mid-range tariff of 18c from Bonkers.ie. Figures are inclusive of VAT.

AIRTIGHTNESS (after, average figures @ 50 Pascals)

n50: 0.55 air changes per hour

q50: 0.4 m3/hr/m2

GROUND FLOOR

Before: Uninsulated concrete floor

U-value: 0.73 W/m2K

After: Existing concrete floor with 20mm Smet floor screed, followed below by 62mm Enviroform E-Therm Slim panels including 2 x 6mm ship lapped mineral boards & 50mm Kingspan PIR floor insulation. Some deeper sections have an additional layer of 50mm QuinnTherm PIR floor insulation. U-value ranges from 0.18-0.23 W/m2K

WALLS

Before: Concrete and brick cavity block walls. U-value:1.78 W/m2K

After, front & rear walls: 12.5mm plasterboard on 15mm dabs internally, followed outside by plastered 215mm Quinnlite B7 Blockwork, externally insulated using Baumit external wall insulation system comprising 200mm Rockwool dual density slab and dry dash finish; some sections with 180mm Rockwool dual density slab and 20mm Ibstock brick slip finish. U-values: 0.14-0.15 W/m2K

After, gable walls: 12.5mm plasterboard internally on 10mm dabs, followed outside by plastered existing 60mm cavity wall with brick outer leaf with 60mm of Kore Diamond BASF 5200 cavity wall insulation, externally insulated using Baumit external wall insulation system comprising 150mm Rockwool dual density slab and 20mm Ibstock brick slip finish. U-value: 0.16 W/m2K

ROOF

Before: 50-100mm mineral wool insulation. Roof tiles to sloped areas, torch on felt and asphalt to flat roof and deck areas externally. U-value: 0.4 & 2.3 W/m2K respectively

After (pitched roof): 12.5mm plasterboard ceilings with airtightness membrane and 400mm of Isover Metac above, between and cross laid over existing ceiling joists. Cold roof space above. U-value: 0.09 W/m2K

After (flat section): Paralon roofing membrane followed below by 140-180mm tapered Paratorch composite insulation, concrete roof, plasterboard and skim finish. U-value: 0.16 W/m2K

WINDOWS & DOORS

Before: Double glazed PVC windows and doors. Overall approximate U-value: 2.7 – 4.8 W/m2K

After: Munster Joinery triple glazed Future Proof PassiV timber aluclad windows and doors. Overall U-value of 0.80 W/m2K

HEATING SYSTEM

Before: 20-year-old gas boiler & radiators.

After: Nilan Compact P exhaust air heat pump w/ heat recovery ventilation distributing heat through ventilation ducting. Plus, three small electric radiators in each apartment, controlled by the Nilan unit.

VENTILATION

Before: No ventilation system. Reliant on infiltration, chimney and opening of windows for air changes.

After: Nilan Compact P — Passive House Institute certified to have heat recovery rate of 75%.