Marley Eternit Profiled Sheeting helps create Passivhaus

Marley Eternit fibre cement profile sheeting has been specified on nine PassivHaus dwellings in Inverness, Scotland, because of its environmental credentials. The properties were designed by HLM Architects, who also chose fibre cement Profile Sheeting in black because it created a visual link with traditional buildings in the Inverness area. Built as part of the Scottish Housing Expo, Profile 6 was specified on the roofs of the properties, whilst Profile 3 was used for the decorative rainscreen cladding on the walls around the entrance to the houses. All materials used on the development were carefully selected because of their environmental credentials. UK manufactured fibre cement profiled sheeting was specified because it achieves an A+ rating in the BRE (Building Research Establishment) Green Guide to Specification based on generic rating for UK produced profiled air cured fibre cement sheeting (outer skin) - (Element Ref: 1012550002). Marley Eternit is currently the only UK manufacturer of fibre cement profiled sheeting. The architects on the project designed the properties to the extremely high performance standards set by PassivHaus. This required an annual heating demand below 15kWh/m² - the properties achieved 14kWh/m². In PassivHaus design air tightness is critical, too, and has to be less than 1m³/hr/m². Using a closed panel construction method for the wall, floors and roofs, pressure testing of the dwellings confirmed that they achieved 0.9m³/hr/m² and therefore within PassivHaus standards. This level of airtightness is 10 times better than Scottish Building regulation requirements of 10m³/hr/m², giving an indication of the performance levels expected in these types of buildings. The interlocking closed panels consists of timber ‘I’ joists and 250mm of mineral wool insulation, encased within a rigid board outer. Externally the panel is supplied with a thermal foil building membrane pre-fitted and internally a pre-fitted thermal vapour barrier provides the main air tight seal. Walls, roofs and floors on the properties achieved a U value of 0.1W/m²k. The Marley Eternit profiled sheeting was mechanically fixed to 75mm timber purlins anchored to the closed panels on the walls and roof. This created the rear ventilated cavity, which provides the building with additional guaranteed levels of performance. Overall the walls were 400mm thick, made up of 245mm joists with 10mm boards either side and 115mm zone for the rainscreen panel and ventilated cavity. "PassivHaus is about getting the envelope working hard in terms of thermal bridging, U values and air tightness, and then orientating the dwelling so that solar gain from the sun provides the small heating requirements," explained Ross Barrett of HLM Architects. "Once we managed to achieve this, we specified fibre cement profiled sheeting from Marley Eternit because of its excellent environmental ratings and pure design aesthetics, which created the perfect finish for the dwellings." The small amount of heating required by the properties is provided by an Air Source Heat Pump (ASHP). A heat recovery ventilation (MVHR) system re-uses over 90 per cent of the heat within the properties. The contractor on site was O’Brien Properties, based in Dingwall, Inverness. The Inverness Housing Expo Show finished at the end of August and all nine of the three bedroom properties are now available for sale.

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