How could a timber supply chain based on local forestry products support the delivery of low carbon social housing in Wales? What transformations are required across the forestry, manufacturing and housing construction sectors to deliver such homes at scale? What interventions are needed to have a transformative impact on the supply chain from tree to timber home? These were the key questions investigated by the Home-Grown Homes Project in close collaboration with a network of organisations across the supply chain including local authorities and housing associations in Wales.

Led by Powys County Council and funded by Welsh Government and the EU Rural Development Programme the research project was delivered by Woodknowledge Wales with project partners Cardiff Metropolitan University, Coed Cymru and BM TRADA. It was launched in April 2018 and officially completed in December 2020.

Key findings and recommendations are summarised in the ▸▸ project report. In addition, ▸▸ practical tools and guidance have been developed for social housing developers, architects and engineers, timber frame manufacturers and wood processors, forestry managers and land owners. A full list of project outputs can be accessed on the project background page.

Net Zero Whole Life Carbon Homes

Wales can build net zero carbon social housing by following five principles. This means tackling upfront carbon, energy demand, use of renewables and embodied carbon in order to reduce the overall emissions associated with any proposed development.

Developers, designers and manufacturers can achieve net-zero whole life carbon with the supporting guidance documents. Government should review policies and set the regulatory framework to achieve net zero whole life carbon housing across Wales.

Minimise Embodied Carbon

Measurement and embodied carbon reduction targets are essential:

  1. Upfront carbon (A1-A5 excluding sequestered carbon) emissions of less than 300kgCO2e/m2. The carbon we emit now has much greater impact than carbon emitted in the future.
  2. Embodied carbon (A1 to C4) of less than 350kgCO2e/m2 as per RIBA 2030 Challenge.

See  Embodied Carbon Guidance.

Policies should initially demand measurement and then introduce embodied carbon reduction targets.

Minimise Energy Demand
  1. Total energy use intensity of less than 35kWh/m2/year.
  2. Fabric first approach with space heating demand of less than 15kWh/m2/year as per RIBA 2030 Challenge.

See ▸ Zero Carbon Homes: Timber Solutions for Wales

Part L should be amended to reflect these targets in current building regulation.

Only Use Renewable Energy
  1. Low carbon means not using gas and oil to heat our homes.
  2. Only use sources of renewable electricity.

The biomass subsidy is diverting timber away from the manufacturing and construction sectors and should be reviewed. Wind, solar and tidal alternatives should be given preference over wood fuel as the least carbon efficient use of timber.

Minimise the Performance Gap
  1. Quality assurance is vital to build high performing housing as designed.
  2. Procure quality over price.
  3. Adopt post-occupancy evaluation to verify and disclose building performance.
  4. Measure energy consumption after at least one year of occupation and report building annual peak demand.
  5. Verify embodied carbon data and report average annual carbon content of the heat supplied (KgCO2/KWh).

See Building Performance Guidance.

Construction policies and regulation for better building and more manufactured approaches to delivery should require post completion performance measurement based on these guidelines.

Offset to Below Zero
To deliver net zero whole life carbon an element of offsetting is required.

  1. A factor of safety should be applied to take us below zero to account for uncertainties in calculation methods.
  2. Create woodlands and use timber.
  3. Invest in additional renewable energy capacity off-site.

See Capturing Carbon Investing in Woodlands

In addition to afforestation, stored biogenic carbon in the building should also be recognised as a robust means of offsetting.

Building on Net Zero Whole Life Carbon definitions by the World Green Building council and LETI these five principles ensure that measures to address upfront carbon, energy demand, use of renewable energy and embodied carbon individually do not have an adverse effect on whole life carbon. Find all policy recommendations across Housing, Manufacturing and Forestry in ▸▸ 5 Essential Strategies for Wales.

Featured publications

Innovative housing projects

Find exemplar timber housing projects we have worked with over the past few years. Explore information on construction, innovative products, use of home-grown timber and Welsh manufacturing, carbon impact and building performance

Find out more

Keep up with webinars and training to help you use our guidance documents and implement project findings throughout the year. Explore presentations and results from our conferences and workshops on the events page. Find all articles relating to our research on housing, manufacturing and forestry on the news page. Learn more about the project and how it evolved, meet our research team and find out about project governance and funding, or check our full list of research outputs on the project background page.

Group photo of 16 people standing outside.

The Home-Grown Homes project is the work of many passionate, patient and persistent individuals across a number of organisations in Wales and beyond. We’d like to express our sincere and heartfelt thanks to every single person who has been involved in the journey so far; whether as an official project partner, an interviewee, a workshop participant or by providing feedback on our findings and recommendations. We are immensely grateful for all your inputs, guidance and advice, and mostly for your great commitment to support this endeavour.

The journey continues and we’re looking at best ways to implement, test and further improve our tools and recommendations. Your feedback on our findings is important to us, please get in touch.