Abstract
The study investigated the hygrothermal performance and risk of mould growth in two thermal insulation systems for internal retrofitting purposes; a phenolic foam system with a closed cell structure, and a capillary active diffusion-open lime-cork based insulating plaster. The setup consisted of a 40-feet (12.2 m) insulated reefer container with controlled indoor climate, reconfigured with several holes (1x2 m each) containing solid masonry walls with embedded wooden elements on the interior side and different interior insulation systems, with and without exterior hydrophobisation. Focus was on the conditions in the interface between wall and insulation system, and in the embedded wooden elements. Relative humidity and temperature were measured in several locations in the test walls over two years, and the mould risk was evaluated by measurements and the VTT mould growth model. Findings for the interior phenolic foam system indicated that exposed walls experienced high relative humidity and high risk of moisture-induced problems. Exterior hydrophobisation had a positive effect on the moisture balance for the southwest oriented wall with phenolic foam. The lime-cork based insulating plaster showed high relative humidity and risk of moisture-induced problems, with and without hydrophobisation.
Highlights
A high energy saving potential is found in retrofitting of historic masonry external walls [1]
This paper presents a large field study comprised of several solid masonry walls with embedded wooden elements and internal insulation for up to two years
The hygrothermal performance of two insulation systems were assessed, and the risk of mould growth was determined through mathematical models and on-site testing
Summary
A high energy saving potential is found in retrofitting of historic masonry external walls [1]. Studies have shown average-weighted U-values of 0.83 and 1.12 W/m2·K for external walls in multi-story residential buildings built prior to 1850 and the period 1850-1930, respectively [1] Many of these buildings are worthy of preservation, which often prohibits major exterior alterations. From a building physics point of view, internal post-insulation of solid masonry walls is considered problematic as the reduced heat flow to the existing wall results in a lower temperature gradient and the original wall becomes colder [3], [4]. This increases the risk of interstitial condensation [3], [4]. The aims were: 1) determine the effect of exterior hydrophobisation on the hygrothermal performance of the examined insulation systems, and 2) test whether mathematical mould models would be useful for prediction of mould risk in the interface and embedded wooden elements
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