Climatic Protection of Historical Vaults with Lime–perlite Mortar

Abstract

ABSTRACT This paper presents the results of a full-scale experiment where a newly-developed thermal insulating mortar was applied to four vaults in the medieval church in Annisse, Denmark. The intervention aimed to stabilize climatic conditions, mitigating potentially harmful processes that often contribute to deterioration and decay. Vaults are exposed to soiling by fine particulate matter, discolouration by micro-organic growth, and damage from salt decay, condensation and infiltrating water. The insulating mortar was specially designed to overcome deficiencies and challenges posed by traditional insulating materials. A highly porous aggregate, perlite, constituted the mortar’s main component. Mixed in a ratio of 6:1 (v/v) with slaked lime, it was applied in a 100mm-thick layer. Upon setting, this layer was covered by a 10mm-thick layer of hair-reinforced slaked lime mortar, which provided a supporting surface. The performance of the insulation mortar was monitored over four years. The moisture from the fresh mortar evaporated slowly during the first two years. Condensation within the insulation did not occur at any time. The thermal insulation reduced the temperature difference between the vault and the inside air, which will impede soiling by thermophoresis. The insulating mortar reduced energy consumption for heating by one third. These results show potential for this treatment in historical buildings.