Performance of a lime-based insulating render for heritage buildings

• Published in: Construction & building materials 2018-01, Vol.159, p.376-389
• Main Authors: Govaerts, Yves, Hayen, Roald, de Bouw, Michael, Verdonck, Ann, Meulebroeck, Wendy, Mertens, Stijn, Grégoire, Yves
• Format: Article
• Language: English
• Subjects: Ageing cycles; Belgium; Building materials; Energy conservation; Hygrothermal modelling; Insulating render; Material characterisation; Perlite; Protection and preservation; Stone imitation
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2017.10.115

•Moisture is stored for a longer time when multiple NHL top layers are applied.•The considered insulating lime render has got a low risk to develop frost damage.•Replacing imitative renderwork by lime-perlite mortar encourages moisture migration.•The render’s thermal insulation efficiency is lower in winter compared to summertime. Insulating heritage buildings in order to provide a comfortable indoor climate, to reduce energy consumption and avoid thermal stresses into the structure, is generally not in accordance with architectural preservation guidelines. Without compromising historic features, insulation renders may however upgrade rendered heritage of which the original materiality is considered inferior compared to its design. This study evaluates the hygrothermal performance of 49 insulating lime-perlite render configurations on brick masonry, by combining characterisation experiments with numerical modelling. The effects of the coupled heat-moisture transport are finally validated by ageing cycles and bond strength tests. It is found that insulating renders cause smaller shifts in temperature in the structure compared to historic renders, but the moisture level of the support may increase significantly. In addition, the insulation layers store a lot of moisture during winter, affecting the expected insulation capacity.