The insulation value of TONZON Floor Insulation


How well do Thermos Cushions actually insulate?



Insulation value indicates how well a material resists heat flow and is expressed as a single number denoting thermal resistance – as an R-value or U-value.
The higher the thermal resistance, the lower the heat loss. This means not only more energy savings, but also a more comfortable temperature inside the home. In short, the higher the insulation value, the better. The minimum insulation value of the TONZON Thermal Cushion is: R-value ≥ 4.8 m²K/W, but this can be much higher in practice. In addition, there is a Thermos Cushion with four chambers instead of three, which provides an insulation U-value ≥ 7.0 m²K/W.



R and U values

Insulation value is abbreviated as either an R-value or a U value. R represents the insulation value of the insulation material, i.e. the insulation that is added to the existing structure. U represents the insulation value of the structure itself. This includes everything - flooring material, floor construction, insulation,etc.
If you add (extra) insulation, in most cases you can just add the R-value of the added insulation material to the U-value of the existing structure.

Rc value Thermos Cushion


The standard TONZON Thermos Cushion for floor insulation consists of three air chambers. A certificate of equivalence has been issued by BCRG for the three-chamber and four-chamber Thermos Cushions. This indicates that a U-value ≥ 5.0 m²K/W may be used when determining the energy label. However, the actual insulation value depends on the thickness of the air layer in the cushions and the type of floor to which the cushions are applied.

Thermos Cushions are made from flexible material. Using wider cushions means the cushions hang down further, increasing the insulation value. How far the cushions can hang down is only limited by the depth of the crawl space.

If the floor is not insulated, the U-value after insulation will be as follows:

U-value (m²K/W) per volume of trapped air 15 cm 20 cm 25 cm
3-chamber Thermos Cushion 5 5,3 5,6
4-Chamber Thermos Cushion 7,1


Wooden floor


Wooden floors require a slightly different approach. In almost all cases, the Thermos Cushions are fixed between the wooden supporting beams, as there are many advantages to placing the insulation material as close to the floor as possible. The disadvantage of this is that the wooden beams interrupt the insulation layer. The insulation value of a wooden floor with 3-chamber Thermos Cushions between the beamsis, according to the norms, U-value = 4.4 m²K/W. For the four-chamber cushion, the U-value = 5.2 m²K/W.

Heat loss through the beams can be reduced by also wrapping them with foil, to eliminate the radiation of heat from the underside of the beams. This provides higher insulation U-values, of ≥ 4.6 m²K/W and ≥ 5.4 m²K/W, respectively.


The BCRG quality declaration assumes that an existing floor has an insulation U-value of 0.15 m²K/W. From this it can be deduced that the added insulation value of the Thermos Cushions is just over R-value ≥ 4.8. For floors where insulation is already present, Thermos Cushions will therefore add a minimum of 4.8 m²K/W to the insulation value. For the four-chamber cushion, if there is enough space to mount it, this value is R-value ≥ 7.0.


Different from other materials

The performance of traditional insulation materials can be expressed in a λ value, which indicates how good the material is at conducting heat. The lower this value, the less heat can flow through the material. Based on this value, it is easy to calculate the insulation value of any thickness of a material.

Due to the unique operation of TONZON insulation materials, no constant λ value can be attributed to them. The insulation value is determined by the amount of air stored in the cushions. According to current standards, the amount of air in the Thermos Cushions contributes less to the insulation value than one would initially expect. This is due to various correction factors. The changes in insulation value relative to the thickness of Thermos Cushions can be seen in the graph. The red line is the insulation value, used in accordance with the standard and the quality declarations.

Experience the comfort of a well insulated floor



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