Project Description

Contractor the Green Build Centre had worked on passive house projects before, but this was  upgrade
ph+ 67 their first Enerphit renovation. “We were very lucky to be honest,” says project manager Mark Higgins, “because basically the house was stripped
back bare. In that respect we had a blank canvas to work with. We stripped out the whole building, ceilings – the lot.”

Retaining the external look of the house meant ruling out one approach that tends to feature prominently in Enerphit projects: external insulation.
But because it was such a big, boxy house, there was sufficient room to accommodate additional insulation internally.

The team then turned its attention to eliminating cold bridges and achieving airtightness. Andrew Shorten points out that external insulation, in
addition to affecting the house’s character, can add a further challenge in a retrofit situation. “With external insulation, there’s now a huge gap between that insulation and the insulation under the floor.”

Shorten argues that insulating internally put him in a better position when it came to designing away cold bridges. Cutting away all floors and ceilings allowed the contractor to completely dryline internal walls. Installing new insulation beneath the floors and in the roof then allowed the team to effectively create a continuous, almost unbroken layer of insulation inside the house.

“If you draw a section through the house,” Shorten explains, “floor meets wall perfectly, wall goes through first floor perfectly, bar timber joists bridging, which isn’t a major deal. Then it goes up and meets the 450mm of attic insulation. “All of the internal walls meet the external walls, creating a break in the insulation but we pumped the cavity with 100mm of bead, so that thermal bridge was nullified by the fact that there was more
insulation out beyond it. It meant the compromise there was really minor.”

Airtightness was then achieved through a combination of OSB board and Siga tape. As has become increasingly common now, the build
contract was subject to a substantial retention – in this case €30,000 – on achieving airtightness.

“We have a system where one person is in charge of the airtightness from start to finish on the project,” says Mark Higgins. “That one person is basically onsite all the time. He’s project leader.”
“When a trade finishes he’ll inspect, and he’ll advise before the trade starts as well. When you tell people that airtightness can cost anything between €5,000 and €10,000 they really don’t understand why – sure it’s only tapes and plastic. They don’t understand the amount of labour that goes into achieving it.”

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