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A low-energy retrofit of social housing in Co. Dublin

The newly renovated Rochestown House complex in Sallynoggin, Co. Dublin, is a great example of how a deep energy retrofit inspired by Passive House principles can transform a damp, cold and draughty concrete block of flats into a set of warm, bright and healthy dwellings.

This high-density social housing complex comprises two blocks of flats designed primarily for elderly residents and those with disabilities. Built in the 1970s, it offered up some of the archetypal challenges of social housing retrofits: the residents didn’t want to move, but the properties failed to meet anything like adequate standards of airtightness or insulation, and needed a major overhaul.

Dún Laoghaire-Rathdown County Council’s architecture department undertook design of the refurbishment in-house, coming up with a series of proposals comprising general refurbishment, expansion of the bedsits, and a significant energy upgrade.

“Since the [recession-led] funding cuts we’ve not had the funds for new-build [but] we’ve always had a refurbishment programme,” says Sarah Clifford, architect with Dún Laoghaire-Rathdown County Council.

The low, outdated standard of accommodation at Rochestown House made its renovation a priority— and offered lots of low-hanging fruit for energy upgrade. “Our aim wasn’t [specifically] Enerphit but it was to do the best refit that we possibly could,” Clifford says. “We really needed to upgrade the existing accommodation; it was very damp.”

The renovation of the smaller Block 2 was done by December 2013, while the bigger Block 1 is close to completion. The aim is to upgrade Block 1 to Enerphit, the Passive House Institute’s retrofit standard. But even though Block 2 didn’t aim for Enerphit, it still applied fabric-first principles of generous and continuous insulation, airtightness, and proper ventilation.

Block 2 is a two-storey concrete block building with a pitched roof. Its cavity walls had no insulation whatsoever prior to its renovation. The orientation of the block is north-northwest to south-southeast. All of the flats were dual-aspect, however the ground floor units had their living accommodation to the north elevation. Also, because of the existing trees and vegetation on the site, solar gain was limited.

A survey by consultant engineers Hanley Pepper got the process underway — and its findings were not good. It was discovered that there was insufficient ventilation and natural light in all ground floor units; while steel sections at balcony level were rusted and in need of repair.

Repair was also needed to various elements of the porches, window sills, and drainage, while re-tanking was recommended for the block’s balcony level. Asbestos was also found on-site. All-in-all, not only was the building envelope insufficient, but there was potential for serious health issues.

Scale was also an issue with the job, but not an entirely negative one: “Quite often the reforms we’ve done before would have been done in [small] lots, broken into packages, whereas with this we were able to it as a [single] job with one contractor,” Clifford says.

The main contractor on Block 2 was K&J Townmore Construction. Director and quantity surveyor Kevin Enright, who has nearly 20 years of experience in the construction area, downplays the difference between this job and any other, at least from the contractor’s point of view: there was a job to be done; and it was done.

“It was much the same, straight-up,” he says. “The spec was sent out and we had to work with that spec.”

The question of scale, however, did come into play, said Kevin, who is responsible for all tender submissions. “It would be, at that level, a new thing for us. We’d have done elements such as mechanical and electrical and so on, but there was never a whole approach before and airtightness was one of the bigger tasks done. It was a high detail job.”

“I have no reservations [about working to the low energy specification]. I won’t say it was an easy job, but it was doable to the specifications laid out,” he says. ““The central thing was the external envelope.”

The initial survey of the block also found ventilation was also found to be non-existent, particularly in the bedsits, which had been unoccupied for some time and were suffering from major dampness and mould-growth problems.

This is hardly unusual for building of the era, but it presented a particular problem given the requirement for much more insulation.

Without due care to ventilation, key energy upgrade measures such as blocking up chimneys and making the building more airtight would have risked further promoting damp and mould growth. A demand-controlled mechanical extract ventilation system was chosen to address this.

Meanwhile the antiquated existing oil-fired district heating at Block 2 was removed, as were the individual hot water cylinders that took up valuable space in each unit. A new district heating system was installed.

The new system foregoes storage tanks completely instead relying on instantaneous heating. Rather than use packaged consumer units, bespoke systems were made on site, including plate heat exchangers for hot water and motorised valves for space heating.

The 12 unoccupied bedsits on the ground floor are now six occupied one-bed apartments, with their internal layout reversed, thus providing a south facing elevation in living areas in order to enhance solar gain. There are a further six one-bed apartments upstairs.

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