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Thermal performance and standards

Thermal conductivity and thermal resistance of insulation materials

The European reference standards for thermal insulation products are
EN 13164 for extruded polystyrene foam (XPS) and
EN 13165 for rigid polyurethane foam products.

These standards define mandatory and optional tests, specimen dimensions,
testing frequency and the criteria used to classify the performance
declared by the manufacturer.

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Each manufacturer is required to provide a
Declaration of Performance, or DoP, which specifies
the essential characteristics of the product, including its declared
thermal conductivity value.

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How the thermal conductivity value is determined

To determine thermal conductivity, the manufacturer collects and analyses
the results obtained through factory production control. The data are
statistically processed to determine the value to be declared in the
product’s technical documentation.

The declared value must provide a conservative representation of the
insulation performance over time and not only the performance measured
immediately after production.

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Initial thermal conductivity and stabilised value

For some insulation materials, the thermal conductivity measured
immediately after production may differ from the value measured after
a certain period of time. Over time, the value tends to stabilise until
it reaches the performance level used for declaration purposes.

For this reason, product standards establish specific procedures for
assessing declared thermal conductivity and taking into account changes
in performance over time.

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Verification and updating of declared values

To determine declared thermal conductivity, the manufacturer must have
an adequate number of results obtained through internal measurements
or tests carried out by external laboratories.

The results are periodically reviewed to ensure that the value stated
in the technical documentation continues to accurately represent
production performance.

The statistical thermal conductivity value is declared using conservative
criteria and is normally stated in increments of
0.001 W/mK.

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Rounding example

If the result of the statistical analysis is
0.033645 W/mK, the declared value will be
0.034 W/mK.

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How thermal resistance is calculated

The thermal resistance of an insulation layer is calculated by dividing
the thickness of the material, expressed in metres, by its thermal
conductivity value.

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Calculation example

Considering an insulation material with a thickness of 80 mm
and a declared thermal conductivity of 0.036 W/mK:

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Declared values for thickness groups

In some cases, a single thermal conductivity value is declared for
a group of thicknesses. This value represents a conservative performance
level applicable to all products included within the group.

A specific thickness may therefore have an actual thermal conductivity
that is better than the general value declared for the group. The thermal
resistance value stated for each thickness must nevertheless be determined
on the basis of the performance applicable to that product.

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Independent quality controls

In addition to the controls required by the production system, Ediltec
periodically submits its products to assessments carried out by qualified
external laboratories and organisations.

For the X-FOAM® range, representative production samples
are tested by the German institute
FIW München, a leading European organisation in the field
of thermal insulation materials.

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Indicative comparison

Thermal conductivity values of selected insulation materials

The values shown are indicative and may vary depending on product type,
thickness, facing and the relevant Declaration of Performance.

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