Superb airtightness result for Manchester ICF house
A new passive house in Manchester, built by Passive Building Structures, has achieved an airtightness test result of 0.31 air changes per hour at 50 Pascals on its final blower door test, easily beating the passive house airtightness standard of 0.6.
This article was originally published in issue 37 of Passive House Plus magazine. Want immediate access to all back issues and exclusive extra content? Click here to subscribe for as little as €10, or click here to receive the next issue free of charge
Passive Building Structures works throughout the UK and Ireland and specialises in a whole-building-fabric approach using insulated concrete formwork (ICF) walls with an insulated raft foundation, plus a lightweight SIPs roofing system.
“Airtightness is an inherent property of our ICF walls because of the monolithic nature of the concrete layer,” Pearce McKenna of Passive Building Structures told Passive House Plus. “However, to get down to the passive house standard, careful planning, attention to detail and quality control on site are critical.
“Airtightness is responsible for a considerable amount of energy loss in typical buildings, and controlling the movement of air is an integral part of the overall reduction of energy demand. The positive effects of high insulation levels and tripleglazed windows are compromised where there is uncontrolled air movement, so controlling unwanted air leakages and then introducing fresh air ventilation is crucial.”
McKenna said that the company utilises the inherent properties of concrete for the performance of its buildings. so careful considerations are made around the concrete design mix, the rate of pour and adequate vibration to ensure consolidation.
McKenna praised Green Building Store, who installed their Progression passive house certified windows on the project, for the quality of their workmanship. “Delivering this level of airtightness performance requires a collective effort from all the trades,” he said.
He also emphasised that a good blower door test result is an indicator of more than just airtightness. “It’s a very important performance indicator in terms of construction quality, workmanship, and envelope integrity,” he said. “It is one of the only performance indicators that is tested on site rather than being based on design figures or assumptions.”
He added: “We will continually strive to improve, make adjustments and further develop our own skills to ensure we consistently deliver on quality and achieve these low levels of airtightness.”
The 5,000 square foot house in Didsbury, Manchester is expected to be completed this summer, and the owner is planning to submit the project for passive house certification. You can follow this project and others on the company’s Instagram page @pbs_icf, or see www.pbsltd.co.uk.