Larch House


Why we like it

The Welsh Future Homes showcase provided an opportunity to build well designed, sustainable houses and demonstrate the value of good design and environmental credentials, focusing on the fabric first approach.

Shortlisted for Chartered Institute of Housing Welsh Housing Awards 2010
Shortlisted for Builder and Engineer Awards 2010
Shortlisted for Sustainability Awards 2010
Shortlisted for Sustain Awards 2011

Welsh Future Homes is a showcase for experimental, low energy homes specifically designed for conditions in Ebbw Vale, and drawing as far as possible on local materials, manufacturing skills and construction expertise. It forms part of The Works, an ambitious £350million development by Blaenau Gwent County Borough Council and the Welsh Government on the site of the former Ebbw Vale steelworks.

The houses are all one-off ‘prototypes’, integrating many features used for the very first time in the UK. These homes include the first solutions for creating a low-cost Welsh version of the Passivhaus energy efficient house, first developed in Germany. The Passivhaus has no need for a conventional gas fired heating system – draught free construction and super insulation in the walls and roof keeps warmth inside the house in winter and maintains cooler, comfortable temperatures in summer.

The Larch House and the Lime House are two of four houses planned for the site, some under construction, some completed.

At the time of construction the Larch House was the UK’s first zero carbon (Code for Sustainable Homes Level 6), low cost, Certified Passivhaus, built as prototype social housing. It was launched at the National Eisteddfod for Wales 2010, held at Ebbw Vale.

Designed by bere:architects, the three bedroom 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.

Passivhaus buildings provide a high level of comfort, whilst using very little energy for heating and cooling. They are built with meticulous attention to detail and with rigorous design and construction according to principles developed by the Passivhaus Institute in Germany, and can be certified through an exacting quality assurance process.

The Passivhaus Standard requires:

  • A maximum space heating and cooling demand of less than 15 kWh/m2 year or a maximum heating and cooling load of 10W/m2.
  • A maximum total primary energy demand of 120 kWh/m2/year.
  • An air change rate of no more than 0.6 air changes per hour @ 50 Pa.

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

Design Process

bere:architects won a construction competition to build a house on the National Eisteddfod festival site at Ebbw Vale, 2010 to showcase the Passivhaus concept. The competition was run by the United Welsh Housing Association, BRE (Wales), Blaenau Gwent County Borough Council and the Welsh Government. One of the standards required was to maximise the use of locally sourced materials, products and know-how.

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.

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 as measured by Paul Jennings, one of the UK’s most respected air testing specialists. 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.

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. Welsh skills, suppliers and products have made the Lime House one of the most energy efficient and cost effective houses ever built in the UK. All of the windows and front door use 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. Most of the timber for the doors, wall panels, floor slabs and roof elements were from Welsh forests with much of the insulation also made in Wales, and the roof tiles coming from a factory only two miles away. The staircase, the stonework and even the solar panels have all been made in Wales.

United Welsh Housing plans to replicate the cutting edge design, technology and techniques of this house in future affordable housing schemes.

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.

Sustainability Credentials EN/CY

Environmental, social and economic benefits:

Low carbon – low carbon housing is a vital element in the drive to achieve greater energy efficiency, reduce carbon emissions and mitigate the effects of climate change. This project shows that building practical, affordable low carbon homes is achievable, and demonstrates a range of measures – such as high levels of air tightness and insulation and use of renewable energy – that designers and builders can use to achieve low carbon buildings.

Brownfield site – the development makes use of a brownfield, former industrial site.

Sustainable, locally sourced 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, while the use of local materials and products reduces the need for transport and use of local know-how increases opportunities for a skilled local workforce.

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.

Over time this will boost the local economy with new jobs, the production of new products, access to new markets, and greater security for existing industries such as timber production.

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. The Code 6 Passivhaus does even better with negative overall costs and an earned balance of £1,400 per annum and the Code 5 Passivhaus achieves an earned balance of £700 per annum.

Larch House achieved Level 6 of the Code for Sustainable Homes.

Designers Evaluation EN/CY

The key outcome other than to achieve Passivhaus certification was to learn lessons from the prototypes and take them forward to larger social housing schemes, stimulating Welsh low carbon industries at the same time. The whole project will be carefully monitored through the Technology Strategy Board (TSB) scheme, with tenants moving in during 2011.

Using cutting edge design and technology, the very latest in building materials and techniques and some clever thinking, the designers have created a home that is super efficient, low cost to run and a pleasure to live in.

It is important that houses are built with sustainability measures in the building process itself as well as the finished product. The balance has to be right between incorporating greener methods of building, offering benefits to tenants, and providing a service that can be delivered for years to come. The designs will be refined to achieve an economically viable product that can be developed at scale, to an agreed standard, using a local supply chain.

Project Summary 

Full address: The Works, Steelworks Road, Ebbw Vale
Date Completed: July 2010
Project type: Residential
Client/ developer: The United Welsh Housing Association, BRE (Wales), the Welsh Assembly Government and Blaenau Gwent County Borough Council
Architects/designers: bere:architects
Other consultants: Passivhaus Certifiers – BRE (Wales),Services Consultant – Alan Clarke, Substructure Engineer – Bob Johnson Structural Engineers, Quantity Surveyor – E. Griffin Consulting, Passivhaus Windows – Double Good Windows, Timber Frame – Holbrook Timber Frame Ltd, Heat Recovery Ventilation Design – The Green Building Store.

Contractors: Pendragon Design and Build
Planning Authority: Blaenau Gwent County Borough Council
Funding body: Welsh Government and United Welsh Housing Association
Site area (hectares, m2): Size of the building plot: 273m2
Site density & typical unit area: The site is still under development and the master plan proposes a mix of uses including, a learning campus, general hospital, leisure centre, sports pitches, theatre, office space and around 500 homes.

Floor area of the house: 99m2

Parking Strategy/ratio: Two off street parking spaces on the site.