The Natural Fibre Insulation Group (NFIG), hosted by the Alliance for Sustainable Building Products (ASBP), recently held a webinar exploring the practical application of natural fibre insulation within social housing retrofit projects.
Bringing together retrofit practitioners, designers and natural insulation specialists, the event examined both the opportunities and challenges of delivering low-carbon retrofit at scale. Presentations from Kasang Kajang of Ksquared and Chris Brookman of Back to Earth provided valuable insights into funding, procurement, technical design and project delivery, while highlighting the important role that natural insulation materials can play in improving building performance and occupant wellbeing.
Delivering retrofit in the real world
Opening the session, Kasang Kajang outlined the significant challenges facing social housing providers as they seek to improve the energy performance of existing homes. With around 80% of the homes that will exist in 2050 already built, retrofit represents one of the UK’s most important decarbonisation challenges.
The presentation explored the increasingly complex funding landscape available to housing providers, including the Warm Homes: Social Housing Fund and other retrofit support mechanisms. Kasang explained how smaller housing associations often face particular barriers in accessing funding and delivering large-scale programmes.
One example was the North River Alliance, a consortium of smaller housing associations established to access funding opportunities that would have been difficult for individual organisations to secure independently. Through collaboration, members have been able to share expertise, achieve economies of scale and develop programmes that would otherwise be beyond their reach.
A recurring theme throughout the presentation was the importance of maintaining a resident-centred approach. Successful retrofit projects require more than technical solutions. They depend on effective engagement, careful planning and a clear understanding of how measures will affect people’s homes and daily lives.
As Kasang explained, retrofit should be approached as “people first, then fabric, then heat source”, recognising that residents ultimately live with the consequences of every design and delivery decision.
Natural fibre insulation in practice
The second presentation focused on the practical application of wood fibre insulation within social housing retrofit schemes.
Chris Brookman described how wood fibre insulation has become an increasingly important solution for solid wall buildings because of its vapour permeability, hygroscopic properties and ability to manage moisture safely within building fabric.
Unlike more conventional insulation approaches that can restrict moisture movement, wood fibre systems are capable of buffering and redistributing moisture, helping to reduce the risk of condensation and mould when correctly specified and installed.
Drawing on a London-based retrofit project, Chris demonstrated how natural fibre insulation was incorporated into a PAS 2035-compliant internal wall insulation system. The project combined wood fibre insulation with hygrothermal modelling, careful detailing and quality assurance procedures to develop a specification tailored to the specific building characteristics.
A key message from the presentation was that there is no universal retrofit solution. Each building requires individual assessment, particularly when introducing internal wall insulation to older or traditionally constructed properties.
Reducing risk through better design
One of the strongest themes to emerge from the webinar was the importance of understanding moisture risk.
Chris explained how hygrothermal modelling software can be used to assess moisture movement within building elements and evaluate how different insulation strategies are likely to perform over time. This approach allows designers to test different scenarios, identify potential risks and optimise specifications before work begins on site.
The discussion highlighted growing concern across the retrofit sector regarding insulation failures linked to inadequate assessment, inappropriate specifications and poor installation practices.
Speakers argued that natural fibre insulation systems can offer important advantages because of their moisture-buffering characteristics, but stressed that material choice alone is not enough. Good outcomes depend on robust assessment, careful design and proper installation.
Procurement and delivery challenges
The webinar also explored the practical realities of delivering innovative products through existing procurement routes.
Kasang described how framework-based procurement can help housing providers meet funding deadlines and comply with procurement requirements. However, these arrangements can sometimes make it more difficult for specific products or suppliers to be selected, even where they have been identified during the design process.
The experience shared during the webinar demonstrated that successful adoption of natural insulation products often depends on alignment between clients, designers, contractors and suppliers throughout the project lifecycle.
Support from manufacturers and suppliers was also identified as an important factor. Training, technical guidance, installation support and clear communication can all help reduce delivery risks and improve confidence among contractors who may be less familiar with natural insulation systems.
Resident experiences
An encouraging aspect of the discussion was the feedback received from residents following installation.
Although internal wall insulation is often associated with concerns about loss of floor space, speakers reported that residents generally found any reduction in room size to be less noticeable than anticipated. In several cases, occupants commented on immediate improvements in comfort and warmth following installation.
The acoustic benefits of wood fibre insulation were also highlighted during the discussion, with speakers noting that residents frequently report quieter and more comfortable living environments after retrofit works have been completed.
These wider benefits are often difficult to capture through conventional energy metrics alone, but they can have a significant influence on occupant wellbeing and satisfaction.
Looking ahead
The webinar concluded with a discussion about the future role of natural insulation materials within social housing retrofit.
While cost and procurement considerations remain important factors, speakers highlighted the growing interest in bio-based materials because of both their technical performance and their contribution to reducing embodied carbon. Natural insulation products such as wood fibre can store biogenic carbon while also supporting moisture-safe retrofit strategies for existing buildings.
The discussion also highlighted the need for greater awareness of building physics, more training across the construction sector and wider adoption of best-practice retrofit approaches.
The session provided a valuable reminder that successful retrofit is about more than achieving target U-values (see our paper on ‘Finding the Sweet Spot’). Delivering healthy, durable and low-carbon homes requires a whole-building approach that considers materials, moisture, occupants and long-term performance together.
The webinar demonstrated that natural fibre insulation is no longer a niche solution confined to heritage projects. With appropriate design, assessment and quality assurance, it is increasingly being used within mainstream social housing retrofit programmes and helping to deliver better outcomes for both buildings and residents.
Find out more about ASBP’s work on natural fibre insulation here – https://asbp.org.uk/group/natural-fibre-insulation.
