Welsh future Homes – The Larch House and Lime House

Planning and Design Process

A product of Wales

A one-off, with many features used for the very first time in the UK, the Larch House, so named due to its Pembrokeshire larch cladding, is very much a product of Wales. It was built by Pendragon Design and Build contractors from Cwmbran and Holbrook Timber Frame from Bridgend, with a Welsh timber frame structure.  Likewise the Lime House was constructed using Welsh skills, suppliers and products. Of particular note are the windows and front door made from Welsh larch timber, thermally modified on Anglesey. Developed and taken through certification by bere:architects, these are the UK’s first Passivhaus certified doors and windows.

Future homes

The designers were striving for a perfect balance, incorporating greener methods of building and offering benefits to tenants through lower energy bills and improved comfort. The partnership has with this project, brought forward practical innovative solutions which address matters of energy efficiency and carbon reduction while providing homes in which people wish to live.  United Welsh Housing plans to replicate the cutting edge design, technology and techniques of this house in future affordable housing schemes.

Air tightness

The project achieved outstanding draught-free construction, surpassing the Passivhaus standard of 0.6 air changes per hour at 50 Pascals, achieving one of the best air tests in the UK for an above-ground, detached house with a result of 0.197 at 50 Pascals. This result is over three times better than the minimum required by the Passivhaus Institute and 50 times better than required under UK Building Regulations. It is made more remarkable as this is the first time this Welsh partnership has attempted to achieve the Passivhaus standard.

Traditional form

The neighbouring two-bedroom Lime House, named after its external lime render – follows the unfussy form of a traditional Welsh cottage with a simple, compact shape. This minimises the surface area heat loss as well as the amount of insulation needed.

Sustainability Outcomes

PassivHaus

To achieve the Passivhaus Standard in the UK typically involves:

• Very high levels of insulation
• Extremely high performance windows with insulated frames
• Airtight building fabric
• ‘Thermal bridge free’ construction
• A mechanical ventilation system with highly efficient heat recovery

Zero Carbon

The Larch House house is c1000ft above sea level in an exposed and misty hilltop location in Ebbw Vale. In spite of this, most energy needs have been met by heat from the sun, the occupants and appliances. The house generates as much energy from the sun in the summer months (from solar thermal and photovoltaic panels with an estimated feed-in tariff of over £900 a year, and through its glazing), as it uses for the whole year, making it Zero Carbon by the UK definition, at the time.

Local materials

A  strong focus on natural materials delivers buildings with strong sustainability credentials such as low embodied energy and high recycling potential. The use of local timber enhances the economic viability of forests, in addition to reducing the need for transport.

Local economy

The focus on locally sourced, developed and manufactured materials and products, brought employment opportunity and developed local skills – for example, a number of joiners in Wales are now trained to manufacture Passivhaus standard windows. It will also provide a boost to traditional skills such as forestry and joinery.

Value for money

The houses demonstrate that low carbon housing does not have to be prohibitively costly to construct. These CSH level 5 and 6 homes cost between £1,300 and £1,700 m² to build, (which compares with average cost of CSH level 3 social housing £1,200 m²). They also offer reduced operating expenses, with heating costs of as little as £80 per annum