What Is An R-Value - Aerolite Insulation

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When we talk about an insulating material’s resistance to conductive heat flow, we talk about its R-value. “R” stands for Resistance to heat flow. It is also sometimes referred to as  Thermal Resistance Value (TRV), and it measures how effectively a material slows the flow of heat from a warmer to a colder area. The higher the R-value, the greater the insulation capability of the material.

It’s important to remember that the R-value of a particular insulation material is the R-value of the product only – not the total insulation of the building as a whole. The walls, ceilings and roof of the building do provide some insulation on their own, which should be added to the value of the insulation material to obtain a final R-value. In addition, the pitch (or angle) of the roof, also affects the overall insulation. Walls have a different R-value to ceilings or roofs because they don’t experience thermal bridging (the phenomenon by which heat flows more easily through studs and joists).

The R-value of new insulation material is calculated according to several factors, including its thickness and density. The basic formula is: the thickness of the insulating material divided by its thermal conductivity. When looking at the R-value of insulation that has already been installed, additional factors – such as how old the material is, how much moisture it’s accumulated, and the ambient temperature – are also taken into account. R-value is measured through a series of industry standard tests – always look for insulation companies that have had their values certified by the South African Bureau of Standards (SABS).

Legislation Affecting R-Values

Three years after the near collapse of our energy grid in 2008, the National Regulator for Compulsory Specifications (NRCS) published legislation governing the energy use in new buildings. This new legislation took the form of SANS 10400-XA, an amendment to the National Building Regulations. From a building perspective, this new ruling divided South Africa into six climate zones, each one with its own minimum R-value required for thermal insulation in all new buildings.

These zones are:

•  Temperate Coastal

•  Arid Interior

•  Cold Interior

•  Temperate Interior

•  Hot Interior

•  Sub-Tropical Coastal

The R-values were calculated according to each climate zone’s temperature and humidity variations. Since the passing of SANS 10400-XA all insulation products must state the R-value of the product on their packaging.

Aerolite has a variety of thicknesses according to the R-value required for your climate zone:

•  Aerolite 135mm – Temperate Coastal, Arid Interior or Cold Interior

•  Aerolite 115mm – Temperate Interior

•  Aerolite 100mm – Hot Interior, Sub-Tropical Coastal

In addition, Aerolite 50mm and 75mm can be installed as a top-up for homes that already have some insulation, but do not yet meet the minimum requirements for adequate insulation. For more information on the different climate zones, click here to see a handy map. And if you’d like to know more about calculating the R-value of your home, talk to the experts at Aerolite.