High-accuracy thermal resistance measuring system with 2 measurement locations

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TRSYS01 is a high-accuracy system for on-site measurement of thermal resistance, R, thermal conductance, the Λ-value, and thermal transmittance, the U-value, of building envelopes. TRSYS01 is mostly used for measurements according to standard practices of ISO 9869 and ASTM C1155 / C1046. The system is equipped with high-accuracy electronics, two heat flux sensors of model HFP01 as well as two pairs of matched thermocouples. The two measurement locations provide redundancy, leading to a high level of confidence in the measurement result. The high accuracy of the heat flux sensors and temperature difference measurements ensures that TRSYS01 continues measuring when other systems no longer perform; in particular at very low temperature differences across the wall.


On-site measurements of thermal resistance, R, are often applied in studies of buildings. Alternatives are to measure its inverse value, the thermal conductance which is called the Λ-value, or the thermal transmittance which includes ambient air boundary layer thermal resistance, the U-value. The measurements of R are based on simultaneous time averaged measurement of heat flux Φ and differential temperature, ΔT, (using two temperature sensors on each on a different side of the wall).

R = ΔT / Φ

The ISO and ASTM standards give detailed directions concerning the measurement method, sensor installation and data analysis. The TRSYS01 system employs dedicated sensors and electronics. Their high accuracy and sensitivity ensure that TRSYS01 will still measure under circumstances where competing systems no longer perform reliable measurements; i.e. down to very low heat fluxes and low temperature differences across the wall. The matched thermocouple pairs in TRSYS01, model TC, measure temperature differences with an uncertainty of better than 0.1 °C over the entire rated temperature range. TRSYS01 includes 2 x HFP01 heat flux plates. HFP01 is the world’s most popular sensor for heat flux measurement in studies of buildings.

The system generates a measurement file, including time, heat flux, temperature and temperature difference for the two measurement locations. The measurement is stored in the MCU01 measurement and control unit, and later downloaded to a PC. Software is included. The user is responsible for data analysis, calculating the R-value or U-value of the building envelope according to the ISO or ASTM standards.

Calibration & conformity assessment

Calibration of TRSYS01 components is traceable to international standards. HFP01 and MCU01 are traceable to the international standards for voltage, current and length, the thermocouples to ITS-90. TRSYS01 undergoes a functional test at the factory. This conformity assessment includes temperature difference measurement accuracy.

Suggested use

  • building U-value and R-value measurement

Expert training in thermal measurement

The measurements and the analyses that have to be performed are not straightforward; although the measurements are standardised, this always involves a significant element of expertise and a subjective data interpretation. Hukseflux helps to gain the necessary experience by offering operator training. Training vastly improves the level of service to the end user, the efficiency of working with the equipment and reduces the uncertainty of the end result. Please contact us for more information on training courses in thermal measurement at Hukseflux.


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