Granaries (horreos) are bioclimatic conservation structures with various forms that have been used for over 2000 years in different countries across Europe and Asia. Galician raised granaries built upon "staddle stones" (pillars with a rodent-proof cap) are specialised barns. The importance of airflow in the preservation of stored grain is based on the use of air as an energy exchange fluid for exchanging heat or water with the grains. The preservation system is based on continuous ventilation inside the bin. Some granaries do not have a wooden slatted floor with gaps, although they should. The gapped, slatted floor particularly influences the thermodynamic behaviour, which is powered by solar radiation, improving ventilation efficiency and internal temperature regulation. This paper shows the important influence of floor grooving on improving grain conservation via better ventilation and limiting the rise in the internal temperature when the granary is subjected to solar radiation. (C) 2011 Elsevier B.V. All rights reserved.