Evaluation of traditional grain store buildings (hórreos) in Galicia (NW Spain): analysis of outdoor/indoor temperature and humidity relationships

Horreos are traditional rural buildings of northern Spain used for desiccation and conservation of cereal grains. They provide natural ventilation, an unfavourable environment to discourage attack by biotic agents (e.g., fungi and insects) and prevent access by others, such as rodents. The objective of this paper was to study the environmental conditions of the Mondonedo type of horreos (north coastal area of Galicia, northwestern Spain). They are built of wood and stone, with a prismatic grain chamber isolated from the ground and with ventilation openings on the side walls. In three horreos, over a period of one month, the temperature (T) and relative humidity (RH) of the indoor and outdoor air were measured throughout the day. Maximum and minimum values during three periods (night, morning and afternoon) and at three specific times (9:00, 14:00 and 21:00) were analysed. It was noted that horreos had a dampening effect on RH. When the outdoor humidity was a 90%, the indoor humidity was on average 5.2% lower. If the outdoor humidity was s 65%, the indoor humidity was on average 3.2% higher. When it was around 75%, this effect was at its smallest. This effect was not as remarkable for T. It is concluded that RH and, to a lesser extent, T remain more stable in the horreo than outdoors, providing an appropriate environment for the preservation of grain. Other characteristics (i.e., geographical location, topographic altitude, exposure to the wind and longitudinal axis direction) appear to influence the amount of change experienced by these parameters.