Aleksandar Janković, Biljana Antunović, Ljubiša Preradović

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Thermal transmittance or U-value is an indicator of the building envelope thermal properties and a key parameter for evaluation of heat losses through the building elements due to heat transmission. It can be determined by calculation based on thermal characteristics of the building element layers. However, this value does not take into account the effects of irregularities and degradation of certain elements of the envelope caused by aging, which may lead to errors in calculation of the heat losses. An effective and simple method for determination of thermal transmittance is in situ measurement, which is governed by the ISO 9869-1:2014 that defines heat flow meter method. This relatively expensive method leaves marks and damages surface of the building element. Furthermore, the final result is not always reliable, in particular when the building element is light or when the weather conditions are not suitable. In order to avoid the above mentioned problems and to estimate the real thermal transmittance value an alternative experimental method, here referred as the natural convection and radiation method, is proposed in this paper. For determination of thermal transmittance, this method requires only temperatures of inside and outside air, as well as the inner wall surface temperature. A detailed statistical analysis, performed by the software package SPSS ver. 20, shows several more advantages of this method comparing to the standard heat flow meter one, besides economic and non-destructive benefits.


Thermal Transmittance, Heat Flow Meter Method, Natural Convection and Radiation Method, Software Support, Statistical Analysis

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Antunović, B., Janković, A., Preradović, Lj., 2014, Thermal performance of preschool education building envelope, Proceedings of International Conference Contemporary Achievements in Civil Engineering, Subotica, Serbia, pp. 545-550.

Antunović, B., Stanković, M., Janković, A., Gajić, D., Todorović, D., 2012, Measurement of thermal transmittance in the Rectorate building of the University of Banja Luka, Proceedings of International Scientific Conference Contemporary Theory and Practice in Civil Engineering, Banja Luka, Bosnia and Herzegovina, pp. 37-46.

ISO 9869:2014-1, Thermal Insulation - Building elements - In-situ measurement of thermal resistance and thermal transmittance, International Organization for Standardization, Geneva, Switzerland.

Nardi, I., Sfarra, S., Ambrosini, D., 2014, Quantitative thermography for the estimation of the U-value: state of the art and a case study, Journal of Physics: Conference Series, 547(1), DOI: 10.1088/1742-6596/547/1/012016.

Albatici, R, Tonelli, A.M., 2010, Infrared thermovision technique for the assessment of thermal transmittance value of opaque building elements on site, Energy and Buildings, 42(11), pp. 2177-2183.

Albatici, R., Tonelli, A.M., Chiognac, M., 2015, A comprehensive experimental approach for the validation of quantitative infrared thermography in the evaluation of building thermal transmittance, Applied Energy, 141, pp. 218-228

Grinzato, E., Bison, P., Cadelano, G., Peron, F., 2010, R-value estimation by local thermographic analysis Proceedings of Thermosense XXXII, Orlando, USA, doi:10.1117/12.850729.

ISO 12567-1:2010, Thermal performance of windows and doors - Determination of thermal transmittance by the hot-box method - Part 1: Complete windows and doors, International Organization for Standardization, Geneva, Switzerland.

ISO 12567-2:2005, Thermal performance of windows and doors - Determination of thermal transmittance by the hot box method - Part 2: Roof windows and other projecting windows, International Organization for Standardization, Geneva, Switzerland.

Cucumo, M., De Rosa, A., Ferraro, V., Kaliakatsos, D., Marinelli, V., 2006, A method for the experimental evaluation in situ of the wall conductance, Energy and Buildings, 38(3), pp. 238-244.

Asdrubali, F., Baldinelli, G., 2011, Thermal transmittance measurements with the hot box method: Calibration, experimental procedures, and uncertainty analyses of three different approaches, Energy and Buildings, 43(7), pp. 1618–1626.

Rasooli, A., Itard, L., Ferreira, C.I., 2016, A response factor-based method for the rapid in situ determination of wall’s thermal resistance in existing buildings, Energy and Buildings, 119, pp. 51- 61.

Schild, K., Willems, V.M., 2006, Building Physics - Handbook - part 1, Friedrich Vieweg & Sohn Verlag, Wiesbaden, Germany, 2.21.

Min, T.C., Schutrum, L.F., Parmelee, G.V., Vouris, J.D., 1956, Natural convection and radiation in a panel heated room, Heating Piping and Air Conditioning (HPAC), 62, pp. 337-358.

Awbi, H.B., Hatton, A., 1999, Natural convection from heated room surfaces, Energy and Buildings, 30, pp. 234- 244.

Khalifa, A.J.N., Marshall R.H., 1990, Validation of heat transfer coefficients on interior building surfaces using a real-sized indoor test cell, International Journal of Heat and Mass Transfer, 33, pp. 2219-2236.

Michejev, M. A., 1952, Základy sdílení tepla, Průmyslové vydavateľství, Prague, Czechoslovakia, p. 387.

King, W., 1932, The basic laws and data of heat transmission, Mechanical Engineering, 54, pp. 347–353.

Nusselt, W., 1915, Das Grundgesetz des Wärmeüberganges, Gesundheits-Ingenieur, 38(42), pp. 477–482.

Heilman, R.H., 1929, Surface heat transmission, Mechanical Engineering, 51, p. 355.

Wilkers, G.B., Peterson, C.M.F., 1938, Radiation and convection from surfaces in various positions, ASHVE Transactions, 44, p. 513.

ASHRAE (American Society of Heating, Refrigerating and Air-conditioning Engineer), 2001, ASHRAE Handbook, Fundamentals, American Society of Heating, Refrigerating and Air-conditioning Engineers, Atlanta, USA.

Hens, H., 2007, Building Physics – Heat, Air and Moisture, Enrst & Son, Berlin, Germany, 73 pp.

Binachi, F., Baldinelli, G., Asdrubali, F., 2014, A quantitative infrared thermography method for the assessment of windows thermal transmittance, Proceedings of Latest Trends in Applied and Theoretical Mechanics, Salerno, Italy, pp. 137 – 143.

Antunović, B., Janković, A., Preradović, Lj., 2015, Measurement of thermal transmittance of opaque facade wall and relationship with meteorological conditions, Tehnika, 70(4), pp. 593 – 598.


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ISSN: 2335-0164 (Online)

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