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Ultimately, all the detailed drawings and photos paid off. “We only did one blower-door test and we got 0.37 air changes per hour,” McGuinness says. “So on that day we all had a pint.” Radon was another challenge on site. “The building is in the highest radon gas risk area in Ireland and has exposed granite bedrock rock present in the subfloor void,” he says. To deal with this he specified a stack-based extract system beneath the ground floor slab connected to a radon sump, plus the installation of a radon membrane that’s adhered to the airtight layer. When it came to heating, Ciaran and Mary had originally planned to put in a wood pellet boiler and solar thermal. But when M&E specialist Damien Mullins of Heat Doc came on board, he steered them away from that idea, and towards a Thermia air-to-water heat pump, for the sake of simplicity. “The cost per kilowatt hour of their machines is very good,” Mullins says of Thermia. He says the controls are also excellent, and that the system heats the top of the buffer tank first, so hot water is available instantly. Mullins explains his preference for heat pumps: “They’re nearly like white goods. You don’t have to worry about topping it up with anything. So it’s very clean from a homeowner’s point of view.” At Forster Park choosing a heat pump meant just one device, with one installer, and less maintenance, and this helped to save money too. The heat pump heats a 210 litre thermal store, which has an internal coil that sends instant hot water to all of the taps, as well as supplying two radiators on the ground floor, a towel rad in the upstairs bathroom, and a post heater in the Zehnder MVHR supply ducting. The heat pump gathers information about heat loss from the house, and uses this to decide when it needs to come on, and at what temperature. Often the rads might just come on at 25C for half an hour. “[The heat pump] decides itself what the flow temperature should be,” Mullins says. “Once you commission it, there is a short
period of tweaking. The short period of tweaking tailors the heat pump to the house, and after that it’s matching the heat loss of the house.” The team can monitor the heat pump online to check when it comes on and off, how long it’s running for, and what the internal and external temperatures are. In their first year (or 12.3 months, more precisely) since moving in, Ciaran and Mary — who have two grown children living at home — spent just €190 on space heating and hot water, which breaks down as €55 for space heating and €135 for domestic hot water (including €127 from the heat pump and €7 worth of immersion). As McGuinness explains, this is based on applying an average Irish electricity price to the heat pump’s metered energy use of just 1117.45 kWh, and excludes VAT, levies, standing charges and utility company special offers. McGuinness, who lectures at Dublin Institute of Technology, tasked one of his MSc students with working out how much the passive house elements of the upgrade had cost, discounting ‘do anyway’ items like the new bathroom and kitchen, and changes to the internal layout. He student produced a figure of €84,000, excluding VAT. “That was lower than I expected certainly,” McGuinness says. He believes he can get this down even lower next time. For example, he says creating a zone for MVHR ducting under the first floor ceiling would have been cheaper and easier — from an airtightness perspective — than running all the ducting through the airtight membrane. He had worried about lowering the height of the first floor rooms, but says in hindsight this wouldn’t have been an issue. Ciaran and Mary have been living in the house now for over a year. “There’s been no space heating on, probably since the middle of February,” Ciaran Ryan says. “We were almost looking forward to the cold snaps, just to see how does the house behave.” His verdict? “It’s just spectacular. Everything
is a constant temperature. You get up to go to the loo in the middle of the night and the hallway is the same temperature as the bedroom, and the bathroom is the same.” One of the biggest challenges when they moved in was finding a duvet thin enough to not overheat under. “You come in at any stage, and you don’t have to worry about getting warm, or putting the heat on, or putting on a coat for the first fifteen minutes until the house heats up,” he says. The house received full passive house certification earlier this year, making it the first such retrofit in Ireland. “Ciaran and Mary knew their budget was too tight but were prepared to compromise on everything except the works needed to achieve passive house certification. Their dedication has been justly rewarded,” Simon McGuinness says. “They have shown that the dream of living in a passive house is not the preserve of a wealthy elite. Passive house is for everyone.”
SELECTED PROJECT DETAILS Architect: Simon McGuinness Contractor: Michael Nally & Sons Airtightness products: Ecological Building Systems M&E design & installation: Heat Doc Ltd External Insulation: Saint-Gobain Weber Windows & doors: Munster Joinery Thermal blocks: Quinn Lite Rainwater goods: Wavin Hot water cylinder: Dimplex Cavity insulation: Certainfil MVHR supplier: Zehnder, via Versatile Heat pump supplier: Thermia, via Ashgrove Mineral wool insulation: Rockwool GGBS: Ecocem
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