The paper presents the experimental measurements and numerical simulation of a ground source heat exchanger operating at a cold climate for a passive house ventilation system. The investigated passive house is a detached single-family house without a basement, occupied by a four head family, located in the South of Poland. The measurements cover over one year period and CFD (Computational Fluid Dynamics) simulations are reported for February when system operates at typical for this period and location cold climate conditions. The calculations were made with the CFD ANSYS FLUENT software package. The house and its components are fitted with a data acquisition system that is operational from 2011 and records 139 points at an interval of 1 min. The data reported in the paper were recorded during winter in the year 2011/2012 by an onside located meteorological station and temperature sensors placed at different depths in the ground and at the outlet of the ground heat exchanger. (C) 2013 Elsevier B.V. All rights reserved.