Effective insulation helps to stabilise indoor temperatures, ensuring comfortable temperatures while minimising the need for mechanical heating and cooling, says sustainability-focused sector body Green Building Council South Africa (GBCSA) technical head Dash Coville.

“One of the clearest indicators of a comfortable building is stable indoor temperature. During winter, indoor spaces should remain warm and welcoming, while in summer they should stay cool and comfortable,” he says.

While this can be achieved through consuming energy to heat or cool spaces mechanically, Coville advocates for designing buildings that naturally maintain more stable internal temperatures.

In particular, he suggests passive building design, which leverages orientation, natural ventilation and insulation aligned with local climate conditions to maintain comfortable temperatures.

“Passive design remains one of the most effective ways to improve building performance sustainably. By reducing reliance on complex systems that consume energy and water, buildings become more efficient, more resilient and more comfortable for occupants,” he explains.

Installed within walls, floors and roof spaces, insulation is a critical component of passive design and acts as a thermal barrier, slowing the transfer of heat between a building's interior and the outside environment.

“Much like a travel mug keeps coffee warm without constant reheating, insulation helps maintain comfortable indoor conditions with significantly less energy input,” says Coville.

A well-insulated building is less susceptible to outdoor temperature fluctuations, reducing the demand for mechanical heating and cooling. This results in lowered energy consumption and reduced operational costs and contributes to greater resilience as climate conditions become more extreme.

Further emphasising the importance of effective insulation, South African National Standards (SANS) 10400-XA, which governs energy use in buildings, establishes minimum insulation requirements for new buildings.

However, Coville notes that further efficiencies can be achieved through careful optimisation, adding that realising these benefits requires an integrative design approach, with passive design principles embedded from the earliest stages of a project.

This includes considering factors such as the type of insulation material selected, thermal performance, thickness, placement and installation quality to improve overall building performance.

Material selection is also increasingly important from a sustainability perspective, Coville adds.

Beyond availability and cost, project teams must consider embodied carbon, durability, maintenance requirements, end-of-life implications and manufacturing impacts when specifying insulation products.

He acknowledges that balancing these considerations can be complex, particularly when trying to align performance goals with broader environmental objectives.

Therefore, GBCSA offers green building certification frameworks which help to guide this process by providing measurable benchmarks, technical tools and access to suitably qualified professionals who can support informed design decisions.

The frameworks include GBCSA’s Green Star New Build framework and the International Finance Corporation’s Excellence in Design for Greater Efficiencies tool.

“Green building certifications reward passive design principles at the design and construction stages of a project because they deliver measurable operational and environmental benefits,” says Coville.

Further, certification gives occupants, investors and financiers confidence that a building’s sustainability claims are backed by credible performance outcomes, he adds.

Additionally, the GBCSA and property management company Growthpoint Properties jointly host the Greenovate Student Competition, which encourages students to explore innovative approaches to sustainability in the built environment.

“Previous competition winners have included a student team that developed concepts for fungal insulation panels grown from mycelial substrate, demonstrating how innovation in materials science could contribute to more sustainable and lower-impact building solutions in future,” Coville concludes.