We offer a variety of building physics’ measurements – window, door and multi-layered building material heat transfer coefficients, material thermal conductivity, specific heat capacity, thermal expansion coefficient, and vapour permeability.

We have 20+ years of experience in testing the thermal properties of building materials and buildings using both self-designed and standardized methods and equipment. We have carried out both European-scale and local projects such as the ERDF project: Development, optimisation, and sustainability research of smart solutions for near-zero energy buildings in real climate conditions and INPATH-TES: Development of lecture courses on building physics and thermal energy storage materials.

Window, Door, and Multi-Layered Building Material Heat Transfer Coefficient (U)

We perform window, door and other (multi-layered) building material heat transfer coefficient U [W/(m2K)] measurements according to the EN ISO 899 standards.

We use a calibrated hot box device with the temperature range for both the hot and the cold side from 10 to 40 °C. It has 92 temperature sensors, 56 of these sensors are placed on the sample (32 on the cold side, 24 – the hot one) and the remaining 36 (18 on the cold side, 18 – the hot one) are placed in the surrounding air. The standard measurement window size is 1.23×1.48 m, but samples up to size 1.4×2.1 m can be inserted.

Material Thermal Conductivity (λ)

We determine the heat conductivity λ [W/(m·K)] of both solid and loose materials according to the ASTM C518, ASTM C1784, ISO 8301, DIN EN 12664, DIN EN 12667 standards.

Netzsch 446 Lambda Small can be used to determine the thermal conductivity λ in the 0.007 – 2 W/(m·K) range with 2% precision. The measurement temperature range is from 20 °C to 90 °C. The maximum sample size is 20×20 cm and the maximum thickness is 5 cm.

Taurus TCA 500-P can be used to measure thermal conductivity in the 0.01 – 0.5 W/(m·K) range with 2% precision. The temperature range for the measurements is from 0 °C to 60 °C. The device is intended for relatively large samples from 0×30 cm to 50×50 cm. The maximum sample thickness is 20 cm.

Specific Heat Capacity (cp)

We determine the specific heat capacity cp [J/(g·K)] of both solid and loose materials according to the ASTM C1784 standard. We perform the measurements with Netzsch 446 Lambda small. It can be used to measure the specific heat capacity in the 0.1 – 5 J/(g·K) range with 5-10 % precision. Measurements can be performed in the -20 – 90 °C temperature range. The sample size is 20×23 cm and its thickness – up to 5 cm.

Water Vapour Transmission Rates (sd, μ)

We determine the water vapour transmission rates and other characteristics  (sd, μ etc.) of polymeric films, sheet materials, concrete, stucco, wood, house wrap, woven, nonwoven, and coated textiles, tapes, hygienic, barrier, and medical material using the gravimetric method. We use GraviTest 6400 – 50 mm, where samples can have a maximum height of 5 cm and a surface area of 50 cm2, 6 samples at a time can be placed into the device. The mass resolution is 0.0001g and the measurement time – up to 2 weeks.

Material Thermal Expansion (α)

We measure solid-state linear thermal expansion coefficient α [m/m°C]  using a dilatometer. We use C-Therm DiL, and the temperature range for the device is between 20 and 1600 °C, with a temperature resolution of 0.1 °C. The maximum temperature change rate is 50 °C/min and the maximum sample size change is 4 mm. Samples in the size range of 10 to 50 mm in length and 4 to 22 mm in diameter can be measured.


Andris Jakovičs, Dr. Phys.

Chair of the INM Scientific Council
Head of the Laboratory of Multiphysical Processes

Staņislavs Gendelis, Dr. Phys.

Senior Researcher