Hygrothermal performance of internal insulation in historic buildings

Tessa Kvist Hansen*

*Corresponding author for this work

Research output: Book/ReportPh.D. thesis

Abstract

Global climate change is evident to most, which is why development in the field of renewable energy sources as well as in the reduction of energy consumption is so vital. As the building stock in Europe accounts for 40 % of the energy consumption, we must find possibilities for reducing this figure - not only by the construction of modern and energy efficient buildings, but also through energy retrofitting existing buildings. In these cases, there is a large potential for energy savings, through i.e. low-energy windows, HVAC, and thermal post-insulation of the building envelope. In Denmark, 35 % of the building stock is comprised of historic buildings. These façades are often preservation worthy, and therefore only internal insulation is possible as a strategy for reducing transmission heat losses of the façades.
The application of internal insulation presents potential for other problems, as the existing wall becomes damper and colder, and the risk of interstitial condensation increases. The elevated moisture conditions induce new risks, i.e. the risk of mould growth, wood rot and frost damage. Therefore, moisture safe and robust solutions for internal insulation of solid masonry must be determined. Dynamic simulations are useful tools for prediction of hygrothermal performance of internal insulation. The modelling results however, are naturally highly dependent on the given input. Therefore, the role and relevance of the various inputs is in focus throughout this thesis, as well as conditions contributing to unfavorable moisture conditions.
The purpose of this study was to investigate important parameters with regard to prediction of the hygrothermal performance of internally insulated solid historic masonry with both experimental and numerical methods. Attention was especially given to the effect of wind-driven rain, possibilities with hydrophobization, and the influence of material parameters. Through case studies, the performances of two different internal insulation systems were evaluated. By means of validated hygrothermal simulation models and implementation of predicted future climate, projections of the hygrothermal conditions were calculated and the risks evaluated. A clear but delayed elevated correlation with wind-driven rain and relative humidity behind the insulation was detected in a laboratory study with relatively extreme environmental loads. The effect of wind-driven rain was also apparent through dynamic simulations. However, in situ measurements of wind-driven rain on case buildings did not give definite results on the impact on humidity conditions behind the insulation. Hydrophobization was introduced as a possible measure to prevent water penetration from wind-driven rain and elevated relative humidity behind the insulation in connection with wind-driven rain. The effect of hydrophobization, on water uptake, drying and vapour diffusion was investigated. It was found that hydrophobization in general had a larger effect in brick when compared to lime mortar. Hygrothermal simulations supported these findings, and showed the brick type being a vital parameter. Through dynamic simulations, it was also established that single material parameters, especially water uptake coefficient, had a significant influence on the hygrothermal performance of masonry. Correlations between material parameters were indicated graphically. Linear and logarithmic regression did not, however, yield sufficient models for these correlations.
Original languageEnglish
Place of PublicationKgs. Lyngby
PublisherTechnical University of Denmark
Number of pages193
ISBN (Print)9788778774965
Publication statusPublished - 2018
SeriesDTU Civil Engineering Report
ISSN1601-2917

Bibliographical note

Ph.D. Thesis R-399

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