Internal insulation of solid masonry walls – field experiment with Phenolic foam and lime-cork based insulating plaster

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.

Hygrothermal assessment of four insulation systems for interior retrofitting of solid masonry walls through calibrated numerical simulations

“…The tendencies observed for the PUR-CM and AAC systems were in agreement with the experimental findings in [42]. The observations for the Phenolic foam system in the interface were however contradictory to the experimental findings [43], as progressively decreasing RH levels were found in the field study while the modelling results predicted increased RH levels. The discrepancies could perhaps be related to the problem with incorrect installation of the Phenolic foam system in the field study mentioned in Section 4.1.…”

“…Regarding the reliability of mathematical mould growth models, previous studies [49], [67]- [71] indicate that the mathematical models are not able to precisely predict the extent of the mould growth infestation, but should instead be used to predict the likelihood of mould growth occurring in the structure or as a comparative tool to evaluate different design solutions. The experimental findings from the field study [42], [43] showed large discrepancies between on-site tests and model predictions. The application of the mould-growth model in this study was therefore used to assess the observed tendencies which include temperature, RH and time into the risk evaluation.…”

“…The simulation models were created and calibrated using measurements from a large field experiment constructed at the Department of Civil Engineering of the Technical University of Denmark (DTU) on a test site in Kongens Lyngby, Denmark (55.79°N, 12.53°E) [42], [43]. The experimental setup consisted of several test walls constructed to resemble wall sections of Danish historic multi storey buildings from the period 1850-1930, both in terms of design and materials.…”

“…The parameter variations D1A and D1B were simulated with an outdoor temperature dependent indoor humidity according to EN/ISO 13788:2013 class A and B [47], to investigate the effect of the indoor moisture load. The other parameter variations simulated with the measured indoor RH levels [42], [43]. Note that all parameter variations were simulated with the initial moisture content set according to the experimental measurements, and a second set of models set to 80% RH.…”

Decisive Parameters for Moisture Safe Internal Insulation of Masonry - Long Time Monitoring in Inhabited Dwellings

“…Older masonry may benefit from external rain protection like hydrophobization since it can prevent or at least obstruct the penetration of precipitation by effectively blocking the capillary suction without effecting the vapor diffusion of the wall, as shown in [8] and [17]. However, experimental results on the combination of hydrophobization with internal insulation in solid masonry walls also show in certain studies [25,26] that the effect of hydrophobization not always is positive. Both diffusion open and tight insulation systems are subject to this problem.…”