Given the Welsh Assembly Government’s wholehearted embrace of the U.K.’s Code for Sustainable Homes, and the government’s relatively strict minimum requirements for new housing, the three homes and visitors’ center built for a development in the former mining town Ebbw Vale are likely a source of pride and encouragement.
As we mentioned last summer, two of the houses – a three-bedroom known as Larch House and a two-bedroom dubbed Lime House – were designed to meet the Passivhaus performance standard. Both have since been certified. The third, a three-bedroom unit, is designed to offer near-zero-energy performance. The project’s partners strove to use locally harvested materials and locally manufactured products, all the while keeping construction costs to a minimum.
“We wanted to show how we could build homes that would be affordable and would use local products. This was about Wales doing this ourselves,” Nick Tune, director of building consultancy BRE Wales, told U.K.-based building-news site Building4Change. BRE Wales partnered on the project with the Welsh Assembly Government (the principal funder), the Blaenau Gwent County Borough Council, and the United Welsh Housing Association.
Performance and cost
The Code for Sustainable Homes features a planning-system code structure that ranges from Level 1, which is the lowest rating, to Level 6, the highest. The Welsh government now requires new housing to achieve, at the minimum, a Level 3 rating. Larch House, the first of the three to be built, has been rated at 6, Lime House at 5. Both are framed with local timber. The third house, constructed with a steel frame and a sheathing material developed by the builder, Dragonboard, is designed to achieve a Level 5 rating.
All three houses in the development, called Welsh Future Homes, are equipped with triple-glazed windows and photovoltaic systems. Larch has a 4.5 kW array and Lime a 2.5 kW system, although the building team points out that Ebbw Vale is 1,000 ft. above sea level and relentlessly chilly and misty during the winter, significantly reducing the potential for PV power and passive solar gain.
The PV panels on the third house were manufactured in Wales by Sharp. Local sourcing also extended to the Lime House windows, which were developed by the design team in collaboration with Bayer and two Wales-based firms, Woodknowledge Wales, and Custom Precision Joinery. These windows are, Building4Change notes, the first in the U.K. manufactured specifically for use in Passivhaus construction.
Wood fiber insulation was used for the Passivhaus homes, Icynene spray foam for the Dragonboard home. The exterior walls and roofs on the Passivhaus projects offer about R-59 thermal resistance. Blower-door tests showed impressive airtighness: 0.197 air changes per hour at 50 Pascal pressure difference.
The project team says that building a replica of Larch House would cost in the range of $179 per sq. ft. to $239 per sq. ft. (The average cost of social housing to code Level 3 is $179 per sq. ft.) Construction costs for a house similar to Lime, excluding the PV, would be about $204 per sq. ft.