Gwynfaen is a Welsh word meaning “white” or “fair” stone. It’s also the name of a highly ambitious and sustainable housing development providing 144 new timber homes – constructed using locally grown Welsh timber.
The award-winning project is informed by the impressive, thoughtful placemaking of architects Stride Treglown, who were responsible for the design. On the edge of a town called Penyrheol, near Swansea, the timber frame homes are arranged around a natural landscape, with a village green and community hub at its heart. Gwynfaen demonstrates how a new housing development can prioritise timber and modern methods of construction (MMC) to deliver low-carbon, low-energy buildings that create a genuine sense of community.
Architect’s sketch showing the ‘village green’ placemaking concept
The brief: an eco-village for generations to come
Stride Treglown began working on this forward-thinking project in 2018, explains Rob Wheaton, architect and Associate Director. The client, Codi Group, is an inventive housing association, one of the biggest in Wales. “The brief was essentially to create an eco village: to design homes inspired by nature and the natural landscape,” Rob tells us.
Codi were bidding for funding through the Welsh government’s Innovative Housing Programme. Their funding bid had to be consistent with the Wellbeing of Future Generations Act – a Welsh legal act seeking to ensure that all decisions made by government and local authorities consider impacts upon future generations.
“Thinking in those terms really made the project what it is,” says Rob. “The site is on the edge of the Gower Peninsula, an area of outstanding national beauty. The placemaking was required to encourage outdoor activity and interaction with the landscape, and to bring about social cohesion – making a community.”
Different sizes for different needs
The 144 dwellings are split between social housing, affordable housing, shared ownership, and market sale. They vary in size and type: a range of two, three and four-bed houses and apartments designed in familiar UK typologies such as terraced, end-terraces and semi-detached – all in timber. The Hub building sits at the heart of the community, where two blocks of apartments sit above an open-plan community space on the ground floor.
A small sample of the range of different sizes and shapes that the development is comprised of. Images © Tom Bright.
Creative placemaking
A village green sits at the heart of the development, which also provided an ingenious solution to the site’s topography, aided by civil and drainage engineering from WSP and landscape design from EDP. “There is a slope across the site, from east to west, of around 10 metres,” Rob tells us. “We wanted to use that slope to channel surface water drainage through: to make a natural feature of it.”
The team also carried out a lot of context analysis, looking at the Gower Peninsula and the vernacular of its housing. “The client wanted to source materials locally, so we carried out a lot of research to understand what was typically used now and historically,” Rob explains.
Keeping carbon down with offsite timber frame
Putting together the factory assembled timber frames houses onsite
After considerable research into the timber frame manufacturers available, SO Modular were selected. They have a timber frame factory in Neath, which is only around 12 miles from the site. They also provided a connection to Hale Construction, the contractors, who are part of the same company and are also Neath-based. “We worked collaboratively with SO Modular to develop the timber frame model,” Rob recalls. “We would load their models into our Revit models, and carry out One Click LCA assessments from them.”
Embodied carbon calculation
Stride Treglown used One Click LCA for embodied carbon analysis for the first time on this project. This was back in 2018, before LETI publications or RIBA 2030 targets and before the mainstream industry had begun to grasp embodied carbon.
A significant amount of innovation and experiment went into optimizing what could be done in the factory. “SO Modular put together factory floor mock-ups, so we could test out the details – we tested a mock-up of an eaves-to-wall junction, for example. We also had a test window to try different types of tape for external and internal air sealing.”
The walls were delivered as prefabricated cassettes. The timber frames all use Welsh timber (Sitka Spruce, C16 strength), and they are all insulated with blown wood fibre insulation from Steico. SO Modular invested some funding to buy an X Flock machine, which blows in the wood fibre insulation to the correct pressure and density. An airtight Medite Smartply board with enhanced vapour resistant properties is installed and taped in the factory. Windows are pre-installed into the timber frame system.
The roofs were panelised too – a roof system that was bespoke designed by SO Modular for the project. This allowed the buildings to be fully weather-tight in around four days after delivery of the timber frame. Welsh timber for the wall and roof systems was supplied by sawmillers Pontrilas – in Hereford, just across the border – and BSW Timber.
Making the most of your timber frame manufacturer
“One of the most interesting things about the project for me was working with the timber frame manufacturers so closely, which we don’t often get to do,” Rob tells us.
“When we went out to tender, we specified that the timber frame should use either a closed panel system or a twin-stud approach. We liked the idea of a twin-stud approach, because you can get all the insulation into one zone, with great U values.
“But SO Modular said they could achieve the U values we wanted by using a deeper (single) stud, which simplified the process somewhat and was more cost-efficient.
“Instead of a more standard 140mm timber frame depth, we ended up with 200mm deep studs, with insulation in a cavity within the service zone – all of which got us to our 0.13 U Value. It was great to have the expertise of the timber frame manufacturer suggesting a speedy factory output for this number of homes.”
Cladding the houses in sympathetic style
“A lot of rural settlements around the Gower used stone with a lime render or timber cladding,” Rob states. “We wanted to provide a modern take on that for the homes.”
Accordingly, each house uses one of three different types of cladding: Welsh larch timber cladding; a lime render which sits on a calcium silicate carrier board; and a dark natural pennant stone, which they managed to source from a quarry six miles from the site. The roofs use fibre cement slate, of which 60% of its content is recycled Welsh slate content.
All the timber cladding received fire treatment within the factory as well. “We weren’t obliged to do everywhere, but we did, as there can be a perception with timber-clad, timber-frame homes that there is a potential fire risk.”
Building fabric and low-energy demand were prime concerns for the designs
Hitting ambitious energy performance targets
One major consideration from the clients was the energy performance of the development. “We had a brief from Welsh government to achieve a SAP score of 96% on all dwellings, regardless of orientation or size,” Rob reveals. “At the time the Future Home Standard was still in its infancy; nevertheless we took a fabric-first approach, with excellent airtightness levels, triple-glazing throughout and MVHR installed.”
Airtightness
“In the first project phase, we achieved an airtightness score of around two, but that improved throughout the development,” Rob tells us. “By the second phase we were hitting around 1.5 which is good in itself, but we ultimately got that down to one.”
Electricity
The housing is all-electric. Every home uses air-source heat pumps for heating and cooling, while the rooftop PVs (photovoltaic panels) from Viridian Solar on each house are linked to its house’s battery storage.
Hoare Lea provided net-zero carbon, sustainability consultancy, and mechanical and electrical engineering services. Their engineers worked with Stride Treglown to provide a detailed energy analysis. They assessed the homes’ predicted energy demand and how much of that could be supplied through the home itself. They price-estimated the energy costs at around £31 per month.
Energy prices have changed dramatically since that analysis; nevertheless Rob asserts that they remain on track with predictions. “Some of the energy bills are as low as £35 per month but the average is around £52.”
Overheating analysis
CIBSE TM 59 was used to assess and minimise overheating risks for the housing. Assessed against future weather scenarios, all the housing passed for 2020 and 2050. Even for 2080, the majority of conditions were still being met – and this is all well beyond building regulations requirements.
Homegrown, sustainable housing at scale
“The real push behind the Welsh government funding was to drive innovation: how can you cut carbon and locally source materials for a project at this scale?” Rob sums up.
He admits that in the early stages there were those who said it could not be done – that it would be difficult to source the homegrown timber in sufficient quantity, that it would be challenging to find an engineer to design to C16 timber.
“It was never a given, but at the end of the day we overcame all the barriers. 144 homes is the kind of level that a commercial housebuilder operates at. Gwynfaen is in many ways a demonstrator project – it shows how sustainable housing can be done well.”
This article featured in Issue 11 of Designing Timber – the full magazine can be read here.
