Energy savings and risk of mold growth in apartments renovated with internal insulation

Hygrothermal performance of six insulation systems for internal retrofitting solid masonry walls

“…The absence of measured fungal growth in the Phenolic foam and CorkPlaster test walls was probably caused by the high pH-value (>10) in the materials which made up the interface between the masonry and insulation that is the lime render and adhesive mortar/CorkPlaster, which created unfavourable growth conditions. These observations correspond with the findings in Jensen et al (2020a), Jensen et al (2020c) and Morelli and Møller (2019), where the authors found no measured fungal growth in the masonry/insulation interface in systems applied with high pH adhesive mortars, despite extended periods with critically high RH levels in relation to fungal growth. The Mycometer ® tests for the MW + VB test wall found high levels of fungal biomass (mycelia and spores) on the wooden studwork and above normal background levels inside the mineral wool insulation, which indicate active fungal growth inside the test wall.…”

“…This has led to increased focus on alkalinity of the adhesive mortars. Morelli and Møller (2019) and Jensen et al (2020a) found high pH-value and no fungal growth behind internal insulation after 2 and 4½ years respectively.…”

“…These systems allow water vapour to diffuse outwards through the insulation and condense, and the intention is then that the systems should redistribute the moisture inwards through capillary suction in an attempt to reduce the risk of fungal growth in critical locations such as the masonry/insulation interface (Brandt et al, 2013; Häupl et al, 2004; Scheffler and Grunewald, 2003; Toman et al, 2009). Several studies including (Finken et al, 2016; Häupl et al, 2003; Klõšeiko et al, 2014; Morelli and Møller, 2019; Odgaard et al, 2018c; Pavlík and Černý, 2009; Toman et al, 2009; Wegerer et al, 2015) have observed good performance using various types of diffusion-open and capillary active systems for internal retrofitting. However, other studies (De Mets et al, 2017; Jensen and Bjarløv, 2019; Odgaard et al, 2018a; Scheffler, 2011) observed high and potentially damaging RH levels in the applied diffusion-open and capillary active systems.…”

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

“…pH-value was however not included in the mould model, and the duration of an "initial drying out" period was rather unclear. Morelli and Møller [9] found high pH-value in adhesive mortars 2 years after application. The reliability of some of the widely used mould prediction models were addressed in [17][18], who found that the models should not be used as a means to determine a precise risk of mould but rather to determine the likelihood of mould growth occurring or not.…”

“…In the past two decades, strategies for internal insulation have changed away from diffusion-tight systems to diffusion-open capillary active systems, capable of redistributing moisture to reduce the mould risk. Studies [7]- [9] have observed good performance using diffusion-open capillary systems for internal retrofitting. However, other studies [5], [10] have found better performance for the diffusion-tight systems if rain could be prevented.…”