INSULATION
Cavity wall insulation’ s growing role
Knauf Insulation
Tightening regulations, a changing climate, and the need to reduce energy demand mean that insulating cavity walls is set to become standard practice.
There is growing recognition of the wider benefits that insulation, from thermal control to acoustic comfort and fire performance.
Setting the standard
The introduction of SANS 10400-XA in 2008, and later amendments, made it clear that improved thermal performance would be required of buildings across South Africa. The standard requires that, in most energy zones, external walls include a 50mm unfilled cavity. A long-anticipated update is expected to require these cavities be insulated under defined circumstances. This supports the trend: As standards evolve, insulation will play an increasingly central role in meeting performance requirements and shaping how buildings are designed and constructed.
Building performance matters
The growing uptake of cavity wall insulation is being driven by regulation, and a better understanding of building performance.
In a country where insulation has historically been overlooked, there is increasing awareness that it helps keep heat out – as well as in. As temperatures become more extreme, this has become more important.
Reducing energy use is also a key concern. Mariana Lamont, Executive Director of the Clay Brick Association, says:“ Research by the Clay Brick Association and the University of Pretoria shows that adding a cavity wall can reduce energy consumption by around 30 %, while insulating that cavity can increase savings to as much as 70 %.”
Acoustic performance is another factor gaining attention. As urbanisation increases, so does exposure to unwanted noise. The widespread use of metal roofing can amplify sound from rain and external sources, making acoustic control a growing priority. Insulation can therefore play a significant role in improving internal comfort by reducing sound transmission.
As cavity wall insulation becomes more common, the choice of insulation material has a direct impact on overall performance. Glass mineral wool products such as DriTherm Cavity Slab 37 combine multiple performance benefits in a single solution. In addition to meeting the required R-values set out in SANS 10400-XA: 2021, they provide acoustic insulation, particularly when used alongside ceiling insulation.
Notably, with fire safety regulations aligning to Euroclass standards, non-combustible materials are gaining prominence. DriTherm Cavity Slab 37 achieves a Euroclass A1 reaction-to-fire classification, meaning it does not significantly contribute to the spread of fire, nor produce significant smoke or flaming droplets.
Durability is another key factor for insulation. A water-repellent additive in the slab helps resist moisture ingress, supporting long-term performance and reliability within the cavity wall system.
Reducing energy demand
Des Schnetler, Executive Director of the Thermal Insulation Products and Systems Association SA( TIPSASA, tipsasa. co. za), says:“ External wall insulation is not a‘ nice-to-have’ – it is a scientifically validated, performancecritical component of the building envelope. Improving the thermal resistance of external walls is one of the most effective interventions for reducing energy demand and improving occupant comfort.”
As South Africa responds to rising energy costs, changing weather patterns, and higher performance expectations, cavity wall insulation is becoming part of good construction practice.
Dual-purpose: acoustic and thermal insulation
68 winter 2026 | www. tobuild. co. za