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Passive House Pharmacy – a challenging low-energy project

When Ronan Quirke decided to upgrade his family pharmacy, he looked for the experience of companies he had worked with before.

Paul McNally of the Passivhaus Architecture Company, had previously designed a low energy extension to Quirke’s Georgian home on Anne Street in the town, and local contractor O’Gorman Construction, had built the extension at Anne Street.

“We had a very good contractor,” McNally says. “He was a great contractor we had complete faith in, he had local knowledge of the buildings on the main street in Clonmel.”

As the old building wasn’t a protected structure, Quirke decided to knock it down and rebuild from scratch. He insisted that whatever building replaced it last a lifetime — he didn’t ever want to have to renovate again. “I only wanted to do this once. I certainly didn’t in 20 years want to be faced with a further patch job,” he says.

“I wanted to future proof it,” he says. Quirke asked McNally what the highest standard he could build it to was, and McNally told him about passive house. But Quirke says: “It also had to be cost-effective. I wasn’t going to keep throwing money at the project just to achieve certification for certification’s sake.”

Quirk observes that, for the tradesmen turning up on site during the build — carpenters, electricians, block layers and so on — the project was almost like a training course. “Every tradesman who turned up wanted to learn something about passive house,” he says. “Everyone was doing something they hadn’t done before.”

There were surprises and challenges along the way.  “During the planning and research, we found out that the ruins of Ireland’s second Quaker meeting house formed the walls of our site boundary, so we had an archaeologist on site during all the excavation and demolition works,” McNally says.

Knocking and rebuilding part of a terrace also posed obvious structural challenges. The ground floor of the old building was knocked out by O’Gorman Construction, and a steel frame was constructed to support both the neighbouring buildings and the rebuilt pharmacy. With the steel frame in place, the upper floors of the old building could be demolished.

The steel frame was installed on Foamglas Perinsul blocks to avoid thermal bridging between it and the concrete slab. After demolition, the team looked at various options for constructing the new pharmacy. Concrete block with an insulated, ultra wide cavity proved the most cost-effective.

Though the pharmacy faces south onto O’Connell Street, the ground floor is overshadowed by the buildings on the far side of the road, blocking solar gain.

“The solution was to raise the shop floor ceiling height to a storey and a half and install full height glazing, so that even on the winter solstice, solar gain penetrates the store,” McNally says.

With little scope for glazing on the east and west gable walls, roof windows were installed in the single storey projection to the back to bring in more natural light.

Inevitably on a project as complex as this, airtightness proved to be the biggest challenge. During the installation of precast concrete slabs at second floor level, connecting airtightness membranes were ruptured. Because the concrete hollow core slab-edge was compromised, penetrations (such as for services and stair opes) within the floor had to be sealed individually, whereas had the membrane been protected at the edge, this may not have been necessary. Extensive remedial work was required to get down to the passive house airtightness standard.

But McNally praises his contractor’s persistence in getting the result down to the passive house requirement of 0.6 air changes per hour. “He was never going to give up.”

Contractor Barry O’Gorman says this was the most energy efficient and airtight building he has ever worked on. While he had experience of building down to around one air change per hour before, 0.6 was a different kettle of fish.

“It was a whole new challenge,” he says, adding that in practice the difference between these two figures — which seem so close together — is “massive, it’s unbelievable”.

Quirke was keen to have automatically opening doors for the pharmacy, for the convenience of customers in wheelchairs or with buggies. Custom-made triple-glazed automatic doors from Irish Door Systems were specified.

But in a busy shop the doors open and close constantly, and the resulting heat loss could have threatened the team’s passive house ambitions.

Working with passive house consultants MosArt, the door losses were quantified and modelled. Increasing insulation might have offset the annual load, but it wouldn’t have addressed instantaneous heat losses.

McNally specified a hot air blower inside the shop above the door. The unit draws on heat supplied by the shop’s gas boiler, and warms cool air that enters through the doors. This system has not been called into action during the first heating season, but will cover future extreme events. The small thermostatically controlled condensing gas boiler also delivers heat to a single radiator in the shop.

Quirke also opted to put a new two-storey apartment in the space above the pharmacy.  The project came in on budget, and the pharmacy opened a month ahead of schedule.

McNally undertook post occupancy analysis, with data loggers measuring temperature and humidity inside. Up until Christmas (2014), temperatures in the pharmacy were around 20 to 21C, with no heating on at all. He says the additional heat gains from retail lighting, computers, CCTV and other electrical equipment in the pharmacy are providing the majority of heat load. January and February (2015) saw Quirke using one hour of radiator heat each morning. Passive house certification has been achieved.

The building is warm, comfortable, spacious, energy efficient, properly ventilated — everything you would expect from a passive house. As Quirke says: “It would have been futile to do this exercise and not get those things.”

“I just think it’s a really great thing, that everybody has got something out of this,” he says.“I’ve got a great building and the builders got something out of it, and all the subcontractors down the line got something out of it.”

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