Our paper presents empirical data from a laboratory experiment investigating the performance of an air-to-soil heat exchanger between July and August 2016. Measurements were performed in a laboratory of the Department of Civil Engineering and Building Engineering Physics of the University of Warmia and Mazury in Olsztyn. Empirical data were compared with the results of analytical calculations based on meteorological data for a typical meteorological year.

Contemporary energy-saving mechanical ventilation systems combined with Earth-Air Heat Exchangers (EAHE) can reach high energetic and economic efficiency. The necessary condition for optimisation of ventilation system functioning is the adequate design of EAHE. This requires knowledge of soil temperature distribution in the location of EAHE. It constitutes a complex problem because of the influence of different factors. The correct estimation of soil temperature for a given location can be difficult in the designing process. The designers can rely on simplified calculation models which can, however, deviate from real empirical data. The motivation to undertake this study was to compare real, empirical energy gains with handly calculations based on two different theoretical models of soil temperature distribution. The theoretical models used for comparison were European norm and semi empirical. The laboratory setting including EAHE was located at Warmia and Mazury University in Olsztyn, Poland. Thus it can reflect real condition operations of EAHE in climate conditions of central Eastern Europe. Data were gathered in a winter period between 1 October and 31 December. The results indicate that empirical data deviate from theoretical models. Models tended to overestimate the energy gains from EAHE by 23%.Keywords: earth-to-air heat exchanger, models for calculating the thermal efficiency of earth-to-air heat exchangers *

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