Let us, for the moment, ignore the national imperatives which resulted in the amended National Building Regulations now requiring the installation of thermal insulation in most new buildings in South Africa  – Compliance with South Africa’s commitments in terms of the Montreal, Kyoto and other protocols, the urgent need to reduce electricity consumption, as well as the undoubted health and productivity benefits to the nation – and focus on the rational reasons why individuals and businesses would install thermal insulation in their homes and buildings.
Rationally, one makes changes to make a beneficial difference to your circumstances, be they subsequently improved in economic, productive, health or altruistic terms.
Installing good thermal insulation to new or existing buildings reduces the heat flow both into and out of the building, with the objective of moderating and/or controlling the temperature within. This has the effect of either creating a comfortable living and working temperature, or a predictable and stable thermal environment for HVAC systems to work efficiently, effectively and economically.
How much thermal insulation is required and where it should be installed in the building depends on the location, design, construction materials used, as well as the purpose of the building. The answer to “How much?” is, simply, enough to make the desired difference. Thermal insulation works when one has comfortable buildings to live and work in, changing our behaviour towards the requirement for and use of heating and cooling systems.