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- The insulation value of wall insulation
Rd en Rc
Insulation value is abbreviated as either Rd or Rc. Rd represents the insulation value of the insulation material, i.e. the added insulation. Rc represents the insulation value of the existing structure. This includes everything - the brick wall, cavity, insulation, plastering, etc. If you add (extra) insulation, in most cases you can just add the Rd of the added insulation material to the Rc of the existing structure.
TONZON Rd value
TONZON wall insulation is made up of layers of motionless air, trapped between layers of TONZON foil. This technique stops heat flow by both conduction and radiation. This unique method enables relatively high insulation values to be achieved. For the best effect, each air layer should be at least 2 cm. Which results in an insulation value of approximately Rd = 0.7 m²K/W per air layer or per 2 cm. In the table below, these values are presented by thickness of insulation material. If the air layers are not 2 cm thick and for other unique cases, we have provided an insulation value calculator.
Thickness Construction Rd (m²K/W) 4 2 air layers, 2 Thermosheets 1.35 6 3 air layers, 2 Thermosheets 2.05 8 4 air layers, 3 Thermosheets 2.75 10 5 air layers, 4 Thermosheets 3.5 12 6 air layers, 5 Thermosheets 4.25
Rc value
The added insulation value assumes that only foil and air insulation are used, but this is not always the case. This is because there must be a structure to support the dry liner boards. Such a structure, in turn, creates cold bridges.
If such a structure is already present, for example in the case of wooden beams, the Rd value may be used and the Rc value can be calculated on that basis.
In most cases, however, this structure is included in the construction of the dry liner, and consists of battens or metal studs.
Metal studs, however, are strongly discouraged, as metal is a very good conductor and will therefore greatly detract from the insulation value. Timber battens are preferable, as wood is a relatively good insulator.
Timber battening still has quite an impact on the final Rc value. However, in the case of a dry liner used in combination with TONZON, cold bridges within the structure will be very limited. This is due to the use of thermal bridge breakers. This is one of the reasons that dry lining in combination with TONZON provides very good insulation value per cm of depth, when compared to other insulation materials.
Comparison with other materials
The insulation value of each material depends on the thickness of the insulation package. The thicker the insulation, the higher the insulation value. If you have limited space, it is important to choose insulation material that can achieve a high insulation value while taking up less space. The most commonly used forms of wall insulation are stone wool or rigid foam boards – for example PIR or Resol foam. When making a dry liner using these materials, a cavity of 2 cm must be allowed, this means that the actual insulation value is slightly lower than the insulation value of the material itself.
In addition, wooden battens are used wih dry liners. The wooden battens are actually cold bridges, but using cold bridge breakers in accordance with the TONZON approach reduces this effect significantly.
As an example, compare the above materials for a 10 cm dry liner. Both the Rd of the material and the Rc of the final structure are shown.
| Material | Rd insulation (thickness) | Rc (m²K/W) |
| TONZON | 3.5 (10cm) | 3.7 |
| Resol foam | 4.0 (8cm) | 3.7 |
| PIR foam | 3.0 (8cm) | 3.2 |
| Mineral wool/EPS | 2.0 (8cm) | 2.5 |
The Resol and PIR hard foam boards have a slightly more advantageous Rd compared to TONZON, but due to the required cavity and cold bridges, the insulation values of TONZON and Resol are close to each other. PIR lags slightly behind, while stone wool barely keeps up in terms of insulation value. The thicker the insulated dry liner, the greater the effect of cold bridges, which is why TONZON achieves the highest insulation values, using cold bridge breakers.
Making the decision
When making a decision, factors in addition to insulation value should be taken into account, as each material has its advantages and disadvantages. For example, if the environment is important to you, and you don't want to use a trailer or van to transport the materials, then TONZON is a good choice. If you want material that you can apply fairly easily, with high insulation value, rigid foam boards are a good option. You often pay a bit more for these. Stone wool is a very flexible material and relatively cheap. However, this also requires protective clothing, as the fibres irritate the skin.