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Green Building News

Wales’ Passivhaus Projects Measure Up

Two of three new affordable houses at Ebbw Vale aimed for certification; the third aimed for exceptional energy performance

Image 1 of 3
Ready for occupancy. Larch House, one of the three high-performance homes built for the Welsh Future Homes mini-development. Named for its larch siding, this three-bedroom house is one of the first in Wales to achieve Passivhaus certification.
Image Credit: BRE Wales
Ready for occupancy. Larch House, one of the three high-performance homes built for the Welsh Future Homes mini-development. Named for its larch siding, this three-bedroom house is one of the first in Wales to achieve Passivhaus certification.
Image Credit: BRE Wales
Another prototype in the Welsh Future Homes project is Lime House, a two-bedroom unit with lime-rendered exterior walls, shown here next to the neighboring Larch House. Lime House also has been certified to the Passivhaus standard. The third house in the project features a steel frame and the use of a board product developed by Dragonboard, the builder of the home. The board is designed to serve as a replacement for OSB and plasterboard.

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.

3 Comments

  1. User avater
    Albert Rooks | | #1

    Wood Fibre Insulation
    Richard,

    Thanks for the post.

    You wrote: "Wood fiber insulation was used for the Passivhaus homes, Icynene spray foam for the Dragonboard home."

    Are you able to provide any details on the wood fibre insulation? Do you know if it was in board form or in batts? if exterior board insulation the thickness or layers used?

    Wood Fibre Insulation is really cool stuff. It's always nice to understand the details used in other parts of the world. Hopefully we get to play with it over here. More sooner than later.

  2. User avater
    Mike Eliason | | #2

    albert,
    per this article,

    albert,

    per this article, it's NBT pavaclad
    http://www.ecobuildingmag.com/newsitem.asp?newsID=134

    agreed, would love if this stuff was made locally, the carbon sequestering properties are great, especially given the embodied energy issue.

  3. John O'Brien | | #3

    Nice exterior shades...
    It'd be nice to get some more detail on the exterior shades as well... Have yet to see any residential projects in NA that have used this. Soooo sexy.

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