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Heaven sent

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Historic buildings at St Anne's were re-rendered using a lime-based render

MCO insulated the roofs of the buildings with Rockwool - between 150mm and 300mm depending on the exact location - though sections where internal rooms go right up into the roof pitch couldn't be insulated. A boiler house was also built, housing a 92 per cent efficient Heizomat 200kW wood pellet boiler to heat both new and old buildings. Low surface temperature radiators distribute heat throughout the buildings. "Underfloor heating sometimes isn't great for older people,” says Crowe. “And we were able to put low surface temperature radiators everywhere. The response time is also quite important, and underfloor heating isn't always brilliant when it comes to response time. The other thing about underfloor heating is that older people really like it when they know where the heat is coming from."

Two gas-fired boilers act as a back-up heat source. Solar thermal and PV were ruled out for the moment, but will be considered in future. "We absolutely thought about it, and it could be something they could add at a later date. I suppose whenever you're investing so much money in a wood pellet boiler, you need to get the best value you can out of that. And actually that roof is overshadowed at certain times of the day, so it wouldn't be perfect for solar, though it's still pretty good."

While St Anne's has few green bells and whistles, certain features make it stand out from an environmental perspective: the care taken to restore and reuse old buildings, the clustering of the buildings, the energy efficiency of the new ones, and the use of natural, low embodied energy materials - from wood pellets for heating to the poroton, lime and the green roof itself.

Items including floorboards, granite rubber, cills, windows and doors were also recycled and reused on site. All lighting is low energy CFLs or LEDs, and energy efficient appliances were specified throughout. Ecoblock - a permeable paving system that allows grass to grow while providing support for vehicles - was also used on the grounds. Easyscreed, a self-levelling liquid screed manufactured from pulverised fly ash was used on the the basement floor. A by product from pulverised fuel power stations, PFA displaces the use of Portland cement in the screed. Similarly, Ecocem’s ground granulated blast furnace slag – a by product from the steel smelting process – made up circa 50 per cent of the mix in all concrete pours including the entire basement ground floor slab of all buildings, the lift shaft and capping to retaining walls.

Conservation was clearly a key part of the re-development. As well as paying attention to the appearance of the historic buildings, MCO aimed to maintain as much of the original fabric (both visible and hidden) and to retain the internal pattern of rooms. Ceilings in the villa have been retained and repaired, while structural timbers, floorboards, joinery, chimney and leadwork all underwent major conservation works.

"[The old buildings] were totally overhauled, they hopefully don't look it but they've had a huge amount of detailed work done on them," says Crowe. "We had a very good foreman on the project, PJ Smith, who has a lot of experience dealing with old buildings, and we had a conservation architect as well...The chimneys had to be reconstructed because they were falling, but they're all blocked off so there's no heat loss."

Crowe mentions ‘Energy efficiency in historic buildings’, a recent conference organised by the Irish Georgian Society that he attended. "One of the speakers [Dr Gary White, Crichton Carbon Centre] reckoned his research showed that we're all totally underestimating the embodied energy of building. For example, the energy involved in getting rid of buildings is vast. So I suppose one major plus point of this is that we have kept these buildings."

The clustered form of the complex has environmental pros and cons. "You're inevitably going to get a dark building in the middle of the plan. But you leave more land for other uses and you're reducing heat losses and sharing heat a lot more," says Crowe, who points out that the Sisters’ way of life is inherently green. "They share everything. It's a very sustainable way to live."

Though the Sisters had only just moved back in as Construct Ireland went to print, Sister Anne Doyle says they are quite impressed with their redeveloped home. "It's much more comfortable, and it's more spacious, and it's sustainable, which is something we're very anxious to promote - to cut down on energy loss. It's a comfortable, healthy space."

Selected project details

Client: Sisters of Mercy

Architects: MCO Projects

Contractor: Allen & Smyth Constructions

Conservation architects: John O'Connell Architects

Archaeologist: Irish Archaeological Consultancy

Biomass boiler: Clearpower

New windows & doors: McNally Joinery

Floor insulation: Energy Savers

Poroton block: Formula Building Technologies

Basement floor screed: Jerry Beades Concrete

GGBS: Ecocem

New sash windows: Thomas Mellot Windows

Heat recovery ventilation: Lindab Ireland

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Lenny Antonelli
		About the author:
		Lenny Antonelli is a journalist for Construct Ireland. He has written for the Sunday Tribune, Science Spin, Sustainability and Organic Matters amongst other publications.