This service offers laboratory-based thermal conductivity measurement of construction materials using the Thermal Needle Probe (TNP) method, a standardized and efficient technique particularly suitable for soil-like, granular, soft, or heterogeneous materials. It is especially useful for cases where traditional steady-state methods (like Guarded Hot Plate) are not feasible due to sample format or composition.

The Thermal Needle Probe method, standardized under ASTM D5334, determines thermal conductivity (λ-value) by applying a known amount of heat through a slender needle embedded in the test sample. The resulting temperature rise over time is recorded, and the thermal conductivity is calculated by fitting the temperature-time data to a well-established theoretical model using a non-linear least-squares inversion algorithm.

The apparatus consists of a slender needle probe containing both a heating element and a temperature sensor, along with a data acquisition and control unit. The test is transient rather than steady-state, meaning the sample does not need to reach thermal equilibrium, which allows for rapid measurements (typically within minutes).

This method is ideal for testing powders, loose-fill insulation, moist materials, foams, and non-rigid composites, where sample geometry or homogeneity poses a challenge for other methods. The minimum required sample size is approximately 80 mm × 50 mm, and depending on the material, preparation may include mild compaction or moisture conditioning.

Thermal Needle Probe measurements provide fast and cost-effective insight into thermal behavior, supporting both material development and comparative performance assessment.