The interest in the energy efficiency of buildings and the integration of new technologies to reduce the heating and cooling loads through the building envelope is not new. The European Union (EU) is committed to decarbonising its building stock as almost 50% of the Union's final energy consumption is for heating and cooling, of which 80% is used in buildings. The article analysis the performance of a PV/T system (with a heat mat) for the heat demand of a low-energy two-zone, single-family building during the year. For this purpose, a building model was built in TRNSYS using Multizone building model and TRNbuild in two variants of heating (internal as reference and external). Then the building model was connected to a mechanical ventilation system providing heating during winter for which the heat source is a PV/T system to demonstrate if the heating requirements for the household can be provided during different seasons of the year. Additionally, it was indicated how much energy consumption reduction can be obtained in comparison to the case when a heating unit is used. (C) 2020 Elsevier Ltd. All rights reserved.