• We have come across a few instances where 50mm Iso board and above is been recommended as a ceiling and or insulation to reach the desired R-value,this is a very expensive way to reach the R-value. One must always keep in mind that 40 mm to 110 mm ISOTHERM is chaper per sq than ISO BOARD is.See tables below.

25mm Iso Board R Value .88               R76.90
30mm Iso Board R-Value 1.0              R92.50
40 mm Iso Board R-Value 1.33           R123.50

50 mm Iso Board R-Value 1.67           R154.50


50 mm x 75cm Isotherm R -Value 1 .1      R21.51

50 mm x 1.2m Isotherm R -Value 1 .1      R20.76

100 mm x 75cm Isotherm R-Value 2.2    R42.67

100 mm x 1.2m Isotherm R-Value 2.2    R41.31

One then can come to the conclusion to apply 25 to 30mm ISO BOARD and fill with ISOTHERM to reach the R Value

A)Zone 5 needs a R-value of 2.7 . Using 25 mm Iso Board with R-value .88, apply 100mm ISOTHERM with a R-value of 2.2,total R-Value reached 3.08

B) Zone 1 needs a R-value of 3.2. Using 30 mm Iso Board with R-value 1.0, apply 100mm ISOTHERM with a R-value of 2.2, total R-value reached 3.2

The above is by far the cheapest way to go if one wants ISO BOARD as the finish.

  • If one is using Rhino board which has a R-value of only 0.08 then,

Zone 5 needs 110mm Isotherm
Zone 1 needs 130mm Isotherm

Please note these prices are a average and exclude vat as well as we are taken the deem to satisfy route.

We offer free consulting and have a show room at your disposal, mimicking the different ceiling finishes of ISO Board. For this service, all we ask of you is to refer us to your project manager / builder/home owner to us when it’s time to purchase the products. We are not only the cheapest in town(direct from factory to site) but also can ensure that all involved, are aware of the correct method these two products should be installed. It has also come to our notice certain hardware shops are saying ISOTHERM is not available or the different thicknesses are not produced by ISOTHERM, or there is a three week waiting order. This is all nonsense, which is one of the reasons why we have opened a depot in Pietermaritzburg.

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