roof insulation r-value
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R-value is the most important factor when it comes to Insulating your home. The higher the value the better the Ceiling Insulation will be. The fact is a low value means poor Insulation properties. In the Western Cape, the R-value 3.70 is compulsory on all new builds.

This rating value will be achieved by Installing Aerolite 135mm or the Isotherm 145mm.

In fact, Roof Insulation is now compulsory. When you are thinking of building a new home or renovating an existing one, there are a few things you need to think about before you start. Firstly the country has been divided into different regions and some regions have different R-value ratings. Secondly, it is important to install Roof Insulation with the highest R-value possible.

This is especially true if your home is in South Africa. The reason for this that in South Africa there is a comprehensive set of guidelines that should be adhered to if you want your home to fit into the grand scheme of things, to help in making your home Eco-friendly and avoid complications later on.

One of the most often misunderstood things in the SAN (South African National Build regulations) is the R-Value and that’s what we are going to talk about today in this article. We will exam R-Value, Which ones are applicable where in South Africa and factors that affect R values that you need to know about.

What is Insulation R-Value? 

Put simply, it is the South African National Building Regulations. In fact, the SANS Legislation is a comprehensive set of regulations designed to provide for sustainable living in an age of shrinking resources and higher energy costs.

The Insulation R-Value tells you the insulation materials capabilities based on the thickness of the insulating material. For the Cape region, an Insulation R-value of 3.70 is prescribed this is achieved by insulation your home with eco-friendly ISOTHERM 145mm thick or AEROLITE 135mm thick Insulation.

For this reason, South Africa is divided into 6 zones with different roof insulation requirements for R-Values in each. R-value is determined by (M squared * K/W) for your convenience we have included thicknesses of two of the common insulating materials used in South Africa to show how much insulation is required to give the required Values. The cost of Roof insulation will vary depending on the insulation’s value.

R-value For Different Zones In South Africa

Zone 1 – Johannesburg and Bloemfontein – R-value = 3,7 ( 135mm Aerolite/145mm of Isotherm

2 – Pretoria and Polokwane – R-Value = 3,2 (135mm Aerolite/145mm Isotherm)

3 – Makhado and Nelspruit – R-Value = 2,7 (100mm of Aerolite/110mm of Isotherm)

         4 – Cape Town and Port Elizabeth – R-Value = 3,7 (135mm of Aerolite/145mm of Isotherm)

5 – Durban, Richards Bay, and East London – Value = 2,7 (100mm of Aerolite/110mm of Isotherm)

6 – Kimberley and Upington – R-Value = 3,5 (135mm Aerolite/145mm Isotherm)

You can find the complete set of regulations for buildings here http://sans10400.co.za/


  1. In fact, compressing the Insulating Material reduces its effectiveness and lowers its Insulation value
  2. Air Gaps in the layers of Insulation and at joints and where cabling and venting pass through reduces the insulation’s effectiveness. This will result in insulation R-Value reduction.
  3. It is important to use a professional insulation installer who knows how to seal this type of air flow.


The Roof Insulation R-value is Based on The Sans Legislation Regulations

Insulating with the proper Insulation isn’t that difficult. Once you know which Zone your home is in and then it is simple to lay down the required layer of Roof Insulation, that is required to achieve the necessary  Value stipulated in the SAN for your Zone.

This is not an easy solution if you are a DIYer it is better to hire a professional.  To be sure contact a Roof Insulation installer who will put in the correct amount of insulation.

In fact is SANS is there to help make South Africa become more energy self-reliant. In fact, this saves money on your cooling and heating costs as well, which is a Win-Win for everyone.

Insulation products that achieve the recommendations are the 145 mm ISOTHERM and the 135mm AEROLITE. Insulation will pay for itself in two to three years.

Read more on Aerolite Specification

Read more on Isotherm Insulation Specifications

Need  More Info On R-value Benefits?

Roof Insulation Western Cape has many years of experience in all forms of Roof Insulation. If you would like more info on the various Roof Insulation products feel free to give us a call or CONTACT US.