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Accurate characterization of the transmittance parameter (U-value) is decisive when assessing energy demand or energy consumption of buildings. The U-value of building envelopes is usually estimated using commercial devices. These commercial solutions present several drawbacks such as their high cost, the fact that they require contact sensors to measure the surface temperature on a limited number of points and the difficulty to meet the standards for ideal measuring conditions. To solve these issues, a Hyper Efficient Arduino Transmittance-meter (HEAT) was recently proposed by the authors for monitoring the U-value based on low-cost technology. This system is now completed with the recording of time series of data based on Internet of Things protocols and the use of non-contact temperature sensors. Studying the applicability, in this case HEAT is used for characterizing walls and ceiling of a building room. To check its performance, the obtained results were compared with those derived from standards and conventional building modelling tools. The results show that the developed system is reliable according to the U-values obtained and expected for the monitored elements, with an acceptable range of uncertainty compared to the ones presented in the literature.

Owing to the high energy consumption in the building sector, appraising the thermal performance of building envelopes is an increasing concern. Recently, a few in situ methodologies to diagnose the thermal parameters of buildings have been considered. However, because of their limitations such as low accuracy, limited number of measurements, and the high cost of monitoring devices, researchers are seeking a new alternative. In this study, a novel hyper-efficient Arduino transmittance-meter was introduced to overcome these limitations and determine the thermal parameters of building envelopes. Unlike conventional methodologies, the proposed transmittance-meter is based on synchronized measurements of different parameters necessary to estimate the transmittance parameter. To verify the applicability of the transmittance-meter, an experimental study was conducted wherein a temperature-controlled box model was thermally monitored, and the outputs of the transmittance-meter employed were compared with those captured by a commercial device. The results revealed a high level of reduction in cost and a low range of difference compared with the latter, thereby validating the applicability of the proposed thermal monitoring system.