Onwards and upwards

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Building: 251 m2 detached home & office
Method: External insulation on blockwork
Location: Dartry, Dublin
Standard: Enerphit (passive house retrofit, certification pending)
BER: A3
Heating & hot water bill: €47 per month (to run the compact heat pump for space heating, hot water & ventilation, for a family of six and two home offices. See ‘In detail’ for more)

When architect Peter Nickels took on the The Willows project, he was working for the most demanding of clients: himself. This deep retrofit involved partially demolishing a dated 1970s dwelling and replacing it with a modern, energy efficient, and taller building.

The Willows was not Nickels’ first refurbishment, but it was an opportunity to put his interest in passive design into practice.

“I had refurbished my own home before and I sort of realised fairly soon afterward, within five or six years, that I could have done things differently. In the last ten to 15 years things have changed tremendously in terms of what we’re trying to achieve,” he says.

In 2013 Nickels and his wife Edelle O’Doherty bought the house — a two-storey flat-roofed structure in Dartry, Dublin 6 — with the aim of undertaking an extensive renovation.

When finished, it would have to serve not only as a home to their family of six, but also as an office for both (Edelle works as a nutritional therapist and functional medicine practitioner). “I thought ‘this is an opportunity to do things properly,” Nickels says.

The couple, both widowed and each with two teenage children, had decided to bring their two families together. Buying a house to raise the blended family was a huge stepping stone, Nickels says. They had been renting nearby and had seen the house come up for sale, although at first sight it did not appear to be an obvious choice.

Nickels was working for the most demanding of clients: himself.

“It was one of a pair of identical infill houses which had been built in the side garden of a large Victorian redbrick villa. These houses were completely out of scale and character with their surrounding context – to one side was Sunbury Gardens, a Victorian architectural set piece, comprising three-storey redbrick villas, all protected structures, arranged around a formal landscaped garden. To the other side was a 1990s development of three-storey townhouses.”

The positive thing about this was the existing house had neither aesthetic nor historical value. “I felt pretty free in the design, because of the age of the building,” Nickels says. “There was nothing precious about it, even though we were right next to these protected structures. Whatever we did was going to make it perform better, function better, and look better.”

Nickels received planning permission for the refurb in 2016, but at first the aim wasn’t to go passive. It was only after this that he became an avid reader of Passive House Plus, and subsequently decided to undertake training to become a certified passive house designer.

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“I designed the scheme and obtained planning permission before undergoing passive house training – so although originally it did embody many of the principles of passive house, the scheme needed to be reviewed and the details re-visited before tendering.”

He says this magazine was a big help in finding the right materials and suppliers. “I was looking for passive house performance window systems and external insulation systems, and originally was considering timber frame on the top floor as a lightweight way to extend over the existing structure.”

Technical challenges

Angelo Babos, owner of main contractor Leopardstown Construction, says that working for an architect building his own house only had a positive effect on the project.

“The only thing I could see different from other jobs in terms of the client being an architect was that he was able to make changes in the layout, finish and location of [things like] electricals,” he says.

1 The southern side of the house prior to renovation; 2-5 much of the external wall on the south elevation at ground floor level was removed and replaced with full height glazing, and the relocated kitchen now feels like part of the garden; 6-8 the masonry walls were insulated externally with graphite enhanced EPS with silicon render finish.

Airtightness works included 1 use of blowerproof liquid airtight paint, seen here at the wall-to-floor junction; 2 & 3 use of airtightness membrane behind joist ends and partition walls; 4 Partel Izoperm membrane behind service cavity battens to the roof; and 5 Partel Conexo tape around window frames; meanwhile thermal bridging measures included 6 Schoeck Isokorb thermal breaks; 7 & 8 and Partel Alma Vert structural insulation (seen here in green).

This does not mean the job was easy, though. In fact, soon into the build major problems requiring remedial work made themselves apparent. “We had to dig out some of the old lobby and found the middle wall and back were not strong enough to put another floor on.”

At this point, total demolition was considered. But Nickels says that by now, the importance of limiting the embodied carbon of the build was high on his mind. This guided a lot of the big decisions, such as preserving as much of the existing structure as possible, in spite of the technical challenges.

Some of the original walls had have to be rebuilt for structural purposes, and while Nickels originally wanted to specify timber for the second floor, he ended up using lightweight thermal blocks from Mannok due to concerns over the compatibility of different render systems applied over timber frame and block, and the associated detailing issues.

Thankfully, Angelo Babos and his team were not entirely new to passive house construction.

“I have done other passive house standard building, a lot of upgrading, especially heat recovery ventilation and Part L compliance,” Babos says.

“Because of the changes in regulations over the last few years, architects are keeping an eye on airtightness and upgrading the U-values of walls.”

Although retrofitting is increasingly seen as the only way Ireland can, at least in terms of its housing stock, meet its climate targets, Babos says the sheer amount of skilled labour required should not be underestimated.

“When you have a retrofit it’s much harder than building from scratch,” he says. “It was very hard to go around and make it airtight, you have weak spots to deal with. That made my life and my lads’ life very hard; we had to put a lot of work in to make it right.”

The main airtightness layer was formed by internal plaster on the new walls and existing plaster on old walls, which needed to be re-done in places. Airtightness tapes from Partel were used to seal junctions, while Blowerproof liquid airtight membrane was applied along door thresholds and where the external walls met the concrete slab (below where plaster could be applied).

Babos says that while the job was challenging, the positive side of this is that it was a learning experience, and a better one than you can get in the classroom or workshop.

“Next time will be easier as we learned a lot. When I did a course, back in 2013, we brought techniques from the workshop, but that was a workshop not reality. And when you go outside into the world you have to do a lot of research,” he says.

Nickels says part of his reasoning in choosing Leopardstown Construction was the need for confidence. “We tendered to builders who had passive house experience and passive house training. Angelo came at it with a very rigorous approach, he was thinking things through, methodologies and so on.”

Design for life

1 The roof features three Fakro quadruple glazed timber aluclad roof lights, while the new roof finishes include 2 fibre cement slates to the pitched sections; and 3 bituminous membrane on the flat.

Clues as to how to extend the dwelling lay in the original design: the house had a central staircase and hall, running east-west, dividing the plan into two equal halves, and the roof was flat.

Nickels says: “The obvious design solution was to go up – forming a new stair over the existing straight stair flight, a new second floor comprising a master bedroom to the north, and a spacious home office on the southern side with views out to the trees and the Dublin mountains. This solution provided the space required, without extending the footprint any closer to surrounding boundaries – and brought the house into scale with the three-storey Victorian houses and the 1990s townhouses.”

The decision to build up rather than out also provided another embodied carbon win: it improved the building’s form factor, the surface area from which heat can escape, to such an extent that the house could meet Enerphit, the passive retrofit standard, even without digging up the floor slab. This is despite the fact that there was only 50 mm of insulation underneath.

“This is where the use of the PHPP software really came into its own,” Nickels says, “to analyse and inform important and costly decisions like this.” (Some of the slab did ultimately have to be replaced to allow for underpinning of walls.)

At first floor level, the simple arrangement of the original house meant that the layout could be re-configured to provide four equally sized bedrooms, which were large enough for double beds and work desks, something that will have proved its value in recent months.

“This was the perfect democratic solution for four teenagers studying from home and meant that none of the children had to settle for a tiny ‘box room’ – which is a typical issue in many existing house types,” Nickels says.

At ground floor, the existing plan again made it very simple to swap the kitchen and living room, with the kitchen relocated to the southern side of the house where it has views out to the garden, whilst the living room was moved to the north side, with a large west-facing window, where it is bright in the evening.

Much of the external wall on the south elevation at ground floor level was removed and replaced with full height glazing, so the kitchen feels like part of the garden, and the movement of the sun around the house throughout the day can be fully experienced.

He became an avid reader of Passive House Plus.

With the addition of the extra floor and steeply pitched roof, the house is now much more visible from the street. But the increased scale and massing fits much better alongside the Victorian villas that inspired the house’s design. Their influence is reflected in features such as the prominent street-facing gable and the grouping of windows at first and second floor level (with brise soleil for shading). An existing mature pear tree was also retained to provide summer shading to the south elevation.

The merging of passive principles, aesthetics and meeting the needs of a modern family — all things missing from many mass-produced houses — should be the logical outcome of the reality of construction, Nickels says: it should all be right.

“There’s so much money invested in construction that you have to succeed on all fronts. Reducing embodied and operational energy is obviously critical to all building projects now, but as an architect the challenge is not just to incorporate these requirements but to use them to inform and help generate a contemporary design aesthetic.”

Though it seems unlikely that he would settle for a standard house, Nickels said the pressure created by the surrounding context helped. “There was a real challenge, being surrounded by historic red brick houses, to make a low energy, contemporary design work.”

Additional words by Peter Nickels

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