Greenhouse cultivation is an intensive part of horticulture in Flanders in which large production volumes are accompanied by significant energy consumptions. Demand for energy efficient solutions is rising due to fluctuations and increases in energy prices, ongoing pressure from international competition and incentives from governments in the scope of climate change. Over a two-year period, a compact ventilation concept was monitored in a Belgian semi-closed greenhouse. The installation was one of the first ventilation concepts in Belgium and is based on intensive thermal screening in combination with controlled ventilation. Air flow rates, indoor and outdoor climatic parameters were monitored as well as the energy flows of the ventilation unit, the energy demand of the greenhouse and the crop results. The measured energy consumption of the concept was 9.6% higher than the reference case in 2010, partly due to its location within the greenhouse complex. However, during the second growing season of 2011, two more similar compartments were compared, showing the potential of the ventilation concept with a 12% energy saving. In addition, improved crop growing conditions become possible as the installation allows for a better control of the greenhouse climate. (c) 2012 Elsevier B.V. All rights reserved.