Hygrothermal performance of a brick wall with interior insulation in cold climate: Vapour open versus vapour tight approach

Abstract

Interior insulation of historic buildings is well-studied in Central Europe; however, their conclusions might not be directly applicable to colder climates. Heat, air and moisture (HAM) modelling can be a valuable tool for studying those solutions in different conditions. Recently, incorporating the capillary condensation redistribution (CCR) test into the material characterization process has shown to cause dramatic improvement in correlating hygrothermal modelling results to measurements in certain situations. It is also noteworthy, that the HAM modelling errors made using material data from conventional characterization process can be severely non-conservative. In this article a parametric study of a 51 cm thick mass masonry wall is undertaken to determine the effect of the improved material properties on the reliability of a vapour open ‘capillary active’ autoclaved aerated concrete (AAC) and calcium silicate (CaSi) interior insulation solutions and to compare them to a vapour tight insulation system. A 49-year real weather dataset from Estonia is used. The results show that compared to conventionally characterized material properties the CCR-optimized material data causes more critical conditions directly behind the interior insulation, while having a similar performance in the exterior part of the masonry. The differences occur close to the performance limits and highlight the importance of using the CCR test in material characterization process. The vapour tight and vapour open systems showed a very similar impact on the freeze-thaw cycles and on the maximum ice saturation of the exterior part of the masonry. The vapour open solutions perform better than the vapour tight PIR in terms of frost damage and possible mould growth behind the insulation – even though the advantage has been reduced when using the CCR-optimized material data. Regardless of the insulation solution, a case-specific approach is still required to avoid damaging the original wall and/or the added insulation system.

Capillary condensation redistribution (CCR) test: measurement results of 5 materials and comparison to modelling

“…without taking the CCR test results into account), severely underestimated the moisture content levels reached in the experiment. It is noteworthy that although a conductivity functions of AAC given in [10] were characterized based on CCR measurement results from a similar product presented in literature [16] and agreeing with measurements from a climate chamber study [8], it is still not capable of replicating the high moisture content levels measured in the current experiment (see Figure 4). The possible reasons could be differences in tested materials, but also more severe boundary conditions of the CCR experiment that were used in this study compared to the one which was used to calibrate the material data (here: cold [16]) -therefore, the drying experiment influenced the liquid conductivity function at those moisture contents.…”

“…The possible reasons could be differences in tested materials, but also more severe boundary conditions of the CCR experiment that were used in this study compared to the one which was used to calibrate the material data (here: cold [16]) -therefore, the drying experiment influenced the liquid conductivity function at those moisture contents. When comparing the results from calcium silicate (Figure 5), both ID1780 and CCR-optimized data from [10] performed reasonably well -the moisture content profile is fairly well reproduced, while the mean moisture content of the sample over time is ca 30% underestimated. This can be attributed to the mass loss when cutting and removing sealing tape that was discussed at the end of previous section.…”

“…The materials selected for this study consisted of 2 types of products commonly used for interior insulation and described as "capillary active" -calcium silicate board (CaSi) and autoclaved aerated concrete (AAC [5] (designated there as "CaSi A" and "AAC" respectively). CaSi E and AAC 2016 were the specific materials used in studies [8][9][10] and that have been attempted to be characterized before, but the CCR test had not been performed on them yet. While CaSi E and H are marketed under different brands, AAC 2016 and 2019 are different iterations of the same product by the same brand.…”

“…Some of them were taken from the material database of Delphin and some from previous studies. Two of the CaSi (ID1780 and data from [10]) and one AAC (data from [10]) material datasets had been characterized based on CCR test already while the rest according to conventional methods (drying and water uptake experiments). The existing properties are not modified.…”

On the potential of clustering approaches for hygrothermal material properties based on three degradation risks in solid masonry constructions

“…Even more the conventional characterization process of materials should be reconsidered to fit different types of climates. According to recent study from Klõšeiko and Kalamees (2021) the material characterization incorporating the capillary condensation redistribution (CCR) test showed improvements in correlating the hygrothermal modeling results to measurements in colder climates compared to the conventionally characterized materials.…”