Hygroscopic inertia in museums housed in old buildings

Abstract

The perservation of artefacts in museum collections is profoundly affected by fluctuations in temperature and, especially, relative humidity. Since the late 19th century, many studies have been carried out into the best way to control hygrothermal conditions. Today, however, the focus is less upon visitors comfort than upon ensuring the stability of relative humidity. In old buildings located in temperature/Mediterranean climate zones with strong thermal inertia, and which have pooor ventilation (relative to the volume and number of visitors), seasonal hygroscopic inertia may help to assure the maintenance of ideal conservation conditions. That is to say, active systems may be dispensed with if the buildings passive bahaviour is used to best advantage. This paper describes the indoor climate of a museum in Southern Portugal, analysing its comfort condition, and explores the concept of seasonal hygroscopic inertia nad ways to determine it. It also presents the preliminary results of an experimental study carried out with a flow chamber developed by the Laboratory of Building Physics at the Faculty of Engineering, Univeristy of Porto, into the effect of hygroscopic inertia on reducing peaks of relative humidity. KEYWORDS: Hygroscopic inertia, relative humidity, museums