EN 12667 Determination of Thermal Resistance in Building Materials by Protected Hot Plate and Heat Flow Meter Methods

The European standard “ EN 12667 Thermal performance of construction materials and products - Determination of thermal resistance by shielded hot plate and heat flow meter methods - Products with high and medium thermal resistance ” describes the principles and test methods for determining the thermal resistance of test specimens with a thermal resistance of at least 0,5 m2·K/W using shielded hot plate or heat flow meter methods.

This limit is due to the influence of contact thermal resistances. The upper limit for measurable thermal resistance depends on a number of factors described in this standard, but a single figure cannot be assigned. It is generally applicable to any average test temperature, but the equipment design in this annex is primarily designed for operation between a minimum cooling unit temperature of minus 100 degrees Celsius and a maximum heating unit temperature of plus 100 degrees Celsius (Annex D).

Limits on the average test temperature are imposed only by the materials used in device construction and ancillary equipment. They provide additional limits for equipment performance and test conditions.

It does not provide general equipment design procedures, equipment failure analysis, equipment performance control, or evaluation of equipment accuracy. It provides sample equipment designs that comply with the requirements specified in this standard.

This standard does not provide general guidance and background information (e.g., procedures requiring multiple measurements, such as the heat transfer property to be reported, product-dependent sample preparation, those to evaluate the effect of sample inhomogeneity, those to test samples whose thickness exceeds the capacity of the instrument, and those to evaluate the relevance of the thickness effect).

Because of these limitations, this standard should be used in conjunction with the product standard associated with the product to be tested. While primarily designed for building materials, this standard can also be used for samples made from any material that meets the specified requirements. This standard does not cover measurements on moist products with any thermal resistance or on thick products with high or medium thermal resistance.

In this standard, the principles are determined as follows:

• Equipment: Both the shielded hot plate apparatus and the heat flow meter apparatus used in the tests were designed to produce a unidirectional, constant, and uniform heat flow rate within flat, parallelepiped homogeneous samples in the form of plates. The part of the apparatus where this occurs with acceptable accuracy is located around its center. Therefore, the apparatus is divided into a central measuring section where measurements are taken and a surrounding shield section.
• Measuring the density of the heat flow rate: Once the steady state is established in the measuring section, the density of the heat flow rate is determined by measuring the heat flow rate and the measuring area through which the heat flow rate passes.
• Measuring the temperature difference: The temperature difference between the samples is measured by temperature sensors fixed to the surfaces of the device in contact with the sample or, where appropriate, to the samples themselves.
• Deriving the thermal resistance or transfer factor: The thermal resistance is calculated from the information provided in this standard, provided the appropriate conditions are met. The transfer factor is calculated from additional information on the sample thickness.
• Calculating thermal conductivity or thermal transmittance: The average thermal conductivity or thermal transmittance of the sample can be calculated when the appropriate conditions for defining them and those given in this standard are met.
• Instrument limitations: The application of the method is limited by the ability of the instrument to provide a unidirectional, constant and uniform heat flow rate density in the sample and the ability to measure power, temperature and dimensions up to the required accuracy limit.
• Sample limits: The application of the method is also limited by the shape of the samples and how identical they are in terms of thickness and structure uniformity (in the case of two sample devices) and whether their surfaces are flat or parallel.

Testing is divided into two parts: sample processing and actual measurements. Certain decisions regarding measurable heat transfer properties, sample processing, and test conditions must be made at the beginning of the test. Instructions regarding these decisions should be sought solely in this standard or in the relevant product standard applicable to the sample to be tested.

A test procedure is the complete set of operations performed on a prepared sample as specified in this standard to determine the desired heat transfer property. These may be further divided into conditioning and the remaining operations for running a test with a shielded hot plate or heat flow meter.

After determining the mass of the samples, they must be conditioned to a constant mass according to relevant product standards. Conditioning involves drying, for example, in a ventilated oven, or drying and then equilibrating with laboratory air. The sample itself can be enclosed in a vapor-tight envelope to prevent moisture transfer to or from the sample during testing. The relative mass loss is calculated from the mass determined before and after drying. To reduce test time, samples can be conditioned to the average test temperature immediately before being placed in the instrument.

The thermal performance of building materials and products is crucial because it directly impacts a building's energy efficiency, indoor comfort, and environmental impact. It is considered important in the following respects:

• Energy efficiency: Good thermal performance helps reduce the need for artificial heating and cooling by slowing the transfer of heat into and out of a building. This leads to lower energy consumption and lower utility bills.
• Indoor comfort: Materials with high thermal performance help maintain a constant, comfortable indoor temperature regardless of outdoor conditions. This improves the living and working environment for residents.
• Environmental impact: Reducing the need for heating and cooling contributes to a more sustainable building by lowering greenhouse gas emissions and helps meet climate change targets.
• Durability and performance: Good thermal performance can help prevent problems such as condensation, mold growth, and material degradation that can result from temperature fluctuations and humidity.

Our organization, which has been supporting businesses across all sectors for years through a wide range of testing, measurement, analysis, and evaluation activities, boasts a strong team of employees who closely follow global developments in science and technology and are constantly improving themselves. In this context, we also provide testing services in accordance with the standard "EN 12667 Thermal performance of building materials and products - Determination of thermal resistance using protected hot plate and heat flow meter methods - Products with high and medium thermal resistance."