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

Abstract

The study investigated the hygrothermal performance and risk of fungal growth in a phenolic foam system with a closed cell structure and a diffusion-open and capillary active lime-cork based insulating plaster, for internal retrofitting purposes. The setup comprised two 40-feet (12.2 m) insulated reefer container with controlled indoor climate, reconfigured with 24 holes (1 × 2 m each) containing solid masonry walls with embedded wooden elements on the interior side. Focus was on the conditions in the masonry/insulation interface and embedded wooden elements, and the performance of the two systems were compared to three diffusion-open insulation systems and one diffusion-tight. The effect of exterior hydrophobisation was also investigated. Relative humidity and temperature were measured in several locations in the test walls over 2½ years, and the risk of fungal growth was evaluated by on-site measurements and the VTT mould-growth model. The findings indicate that internally insulated walls with bare brick exterior surfaces performed poorly with high risk of fungal growth. The effect of exterior hydrophobisation was found to vary with the orientation and the installed insulation system, with a generally positive effect on walls facing south-west but limited effect for north-east. Furthermore, the more diffusion-tight insulation systems were found to perform better in combination with exterior hydrophobisation than the highly diffusion-open systems. The lime-cork insulating plaster showed high relative humidity and risk of moisture-induced problems. The on-site fungal tests showed no growth in the masonry/insulation interface inside the two insulation systems, probably due to high initial pH-value.

Internal Insulation – four systems in one historic residential building

“…40% of the total European energy consumption and 30-40% of the total C02 emissions are estimated to be caused by the built environment [1]. A large part of the existing European buildings (almost 60%) was built prior to 1960.…”

“…A large part of the existing European buildings (almost 60%) was built prior to 1960. These cases usually experience high heat losses through the external walls, resulting in decreased indoor thermal comfort [1,2]. Since most of these buildings have facades worthy of preservation because of their historic, architectural or aesthetic qualities, external insulation or renovation techniques are not allowed or are at least limited [2].…”

“…However, internal insulation in solid masonry walls is known to be challenging due to the change in the external wall; it becomes colder and damper, which may lead to interstitial condensation [3]. Moreover, the application of the insulation material can cause reduction in the vapor diffusion to the inside [1]. The aforementioned parameters lead to increased humidity levels in the external wall, therefore, higher risk of moisture-related issues [4,5].…”

Evaluation of moisture diffusion characteristics and the effect of moisture treatment on flexural properties of expanded perlite-based building material

“…However, these foams had been studied only for physical, compressive, and flexural properties. The major application of the expanded perlite-based insulation materials lies in building insulation (Jensen et al, 2021; Wu et al, 2014; Yilmazer and Ozdeniz, 2005) and retrofitting (Orzechowski and Orzechowski, 2018). In the case of building and construction applications, though, a consideration of moisture diffusion mechanism and moisture effect on the mechanical properties of the foams may be inevitable because they are usually exposed to a variety of atmospheric conditions.…”

Empirical Investigation of the Hygrothermal Diffusion Properties of Permeable Building Membranes Subjected to Variable Relative Humidity Condition

“…The problems associated with high indoor humidity, condensation, and mould growth currently prevalent in Australia buildings' cold and humid climate is common in many developing and developed nations, and high-quality material vapour diffusion data is needed to undertake hygrothermal simulations to inform regulatory development [9][10][11]. Considering the global movement towards a zero-carbon economy and its reliance on highly energy-efficient buildings, it is important to acknowledge that airtight and well-insulated envelopes can perform sub-optimally if unmanaged moisture is present [12][13][14][15][16][17]. Aside from building durability issues, this will further affect opportunities to reduce carbon emissions generated through the operation of heating and cooling equipment within buildings [18,19].…”