Builder Niall Dolan of GreenTec Ecological Homes takes no chances when it comes to air tightness. In addition to ensuring that everyone onsite has been trained to the right level, he always makes sure he’s onsite during this critical phase.
This explains the long list of passive standard air tightness results achieved by the houses he has built. Hugh Whiriskey’s masonry build in Craughwell, Co. Galway is no different. This low energy home scored an airtightness result of 0.48 ACH (air changes per hour) at 50 Pascals – well within the Passive House threshold of 0.6 ACH.
“I put everyone I work with on one-day airtightness courses,” says Niall, “and in addition to that, I also train them on site with me.”
Because all trades – and electricians in particular – have an impact on air tightness, Niall also trains all of his subcontractors himself.
“I bring them in for toolbox talks, about air tightness and tidiness and keeping things clipped to walls. They need to know that if they cut a hole somewhere, they must let me know so I can tape it afterwards.”
He also makes sure his own skills remain up to date with constant reading and regular visits to international trade shows. And as the person responsible for how the house will ultimately perform, he also believes it’s vital for him to be on site during the most critical stages.
On Hugh Whiriskey’s Galway house, air tightness comes primarily from the internal wet plaster finish, together with Ampack’s suite of tapes and membranes. “We plastered down to the slabs and put a little bevel on the plaster to seal it,” says Niall, so “we didn’t need to use any tape at the bottom.”
An engineer by profession, Hugh Whiriskey works with architects and consulting engineers, Corbwell Design in Galway. He explains that financial considerations lay behind the decision to go with a masonry build. At the time, the meltdown in construction had seen the price of block laying decline sufficiently to make it that bit more cost effective than timber frame.
He went with a wide – 250mm – cavity pumped with EPS platinum bead. High ceilings and an open plan design also prompted the decision to lay blocks on the flat, giving a 215mm concrete wall. “So you’re automatically getting a very high thermal mass,” Whiriskey explains. “The house retains its own heat at a very comfortable temperature.”
He found however that the detailing required to ensure air tightness and design away thermal bridges was a lot trickier than it would have been with a timber frame. Niall Dolan however is a veteran of several wide-cavity builds. “Niall is brilliant on the details,” says Whiriskey, “he makes that side of things quite easy.”
Quinn Lite blocks were deployed at both foundation and wall plate level to deliver the necessary thermal break, while Teplo wall-ties in the cavity did the same job there. Ply boxes were used behind the windows to close the cavities, but it was detailing the balcony that took most of the thought and energy.
“We were adamant we wanted to keep it cantilevered, unsupported on the far corner,” Whiriskey explains. “Structurally that makes things difficult, and then you’ve got to factor in the thermal bridging as well, so between those two, it consumed a bit of time.”
Concrete upper floors are typically hollowcore; precast slabs are craned into place on top of blockwork, but because Whiriskey wanted an open plan layout downstairs, that approach would have involved large amounts of structural steel in the slabs, which in turn would have had a major impact on cost. Because he also wanted the first floor balcony to extend unsupported over the patio area outside, that too would have required large amounts of steel. This was a non-runner, not alone from a cost point of view, but also because thermally breaking the structure would have been, in Whiriskey’s words, ‘almost impossible’.
The solution was to pour the upper floor in situ, and thermally break the cantilevered balcony using a specialised Schock balcony connector embedded in the concrete. This, says Niall Dolan, was unquestionably the most difficult element of the build. “The air tightness here wasn’t too bad,” he says, “but the balcony and the cold bridging for the poured slab, that really was the trickiest thing.”
Good detailing at the outset was central to the success of the build, he says, as was good communication throughout. Site meetings were held every two weeks to review the schedule and discuss the upcoming phase.
Niall also relies heavily on technology to facilitate on site communication. “I use an app called Plangrid. We download all our drawings to it. That way, you don’t need a signal to use it. All of the guys have smartphones or tablets, and they just call up the app and zoom into the detail they want.”
This approach means that you don’t have the problem of paper maps getting damp on site, and when new drawings are issued, the app ensures that the latest version supersedes the old, keeping everyone on the same page.
Niall also uses a snaglister app. “I do up reports every two to three weeks detailing all the things I need every subbie to do. I take pictures of everything, itemise the rooms, compile a report and email it straight to each of them. Then I go round with the lists on the app. If something’s complete, you just tick it on your phone and if there’s anything outstanding, you reissue the list. Simple.”
The house is heated by a combination of a geothermal heat pump and room-sealed stoves. The latter will be fuelled by home-grown willow; Hugh Whiriskey planted 1.5 acres on the site in advance of the construction phase.
“The theory is, we’ll supply our own timber from it,” he explains. “I tried to work out how much we’d need at the time and planted accordingly. It’s three years down, so in a year and a half, we’ll be cutting one third, and then replanting.”
The Whiriskey family have been in the house now for two years, and so far, so good. “We’re very happy with the build, very happy with the appearance, very happy with how the house is performing. On the whole, I’d say we’re pretty fortunate with how it’s worked out.”