A study of the microclimate within the Hal-Saflieni Hypogeum complex

Abstract

A number of physical parameters which influence the microclimate inside the Hal-Saflieni Hypogeum complex were monitored both spatially and temporarily. Air and wall temperatures, relative humidity/vapour pressure, wall moisture, air current and direction, with Co2 concentration were regularly monitored over a period of two years. Light intensity was also measured, and a weekly record of water infiltration/condensation droplets was kept. Analysis of these data showed that the air temperature and vapour pressure inside the generally followed those at the exterior, but their range of annual fluctuations tended to decrease with increasing depth of the chambers. Furthermore, the wall surface temperature showed similar trends to the mean monthly air , whereas the wall moisture readings showed saturation of the rock walls in almost every chamber. Readings of air currents showed that the Hypogeum has very weak ventilation currents which become less appreciable with increasing distance from the entrance. These are directly related to the presence of visitors, as is also the co2 concentration. Light intensity within the Hypogeum which is solely due to artificial lighting, is very low. The occurrence of water infiltration/condensation, as droplets and pools, tended to follow changes in air vapour pressure.