Moisture-proof energy renovation of conservation-worthy exterior masonry walls

Retrofitting from the inside is often the only option to improve the thermal insulation of older buildings with solid masonry, as you want to preserve the appearance of these buildings. A significant part of the Danish building stock consists of buildings of this type. Brick facades account for a very large part of the facade area built before 1950. Preservation of these buildings, which give character to urban environments, requires maintanence of the brickwork, and that the energy, indoor climate and comfort performance of the buildings is improved to suit into the demands of the future.
Internal retrofitting can in some cases lead to moisture-related damage, because the insulation changes the temperature and moisture conditions in the original outer wall: This becomes colder and more vulnerable to penetrating moisture, e.g. from driving rain or rising damp, or moisture from the indoor climate. Therefore, the desire to save energy and increase comfort must be seen in the context of this risk and which other factors plays in.

The purpose of the project was to obtain the necessary, but still lacking, experience with Danish masonry walls worthy of preservation, and to gather the experience from the international and other national projects into a collective knowledge that makes it possible to describe in guidelines, how conservation-worthy brick exterior walls are energy-renovated in a moisture-safe manner. In the project, an extensive collection of knowledge and experience has been carried out both from already completed research and demonstration projects as well as from measurement projects, simulations and analysis of data as well as other observations carried out in this project.

The project had the following main activities, which support the project's overall purpose:


Hygrothermal Performance of Hydrophobized Brick and Mortar: Energy Renovation Through Internal Insulation - Can Hydrophobization Improve the Moisture Safety?
PhD project at AAU: Vasilis Soulios (2018-2021)
Supervisors: senior researcher Ernst Jan de Place Hansen and head of research Ruut Peuhkuri

Internal insulation of masonry - Hygrothermal performance and robustness in practice
PhD project at DTU: Panagiota Pagoni (2020-2024)
Supervisors: professor Eva B Møller, assistant professor Tessa Kvist Hansen and head of research Ruut Peuhkuri

Collection of experience from "all" Danish projects
Since 2013-14, several Danish demonstration projects with internal insulation have been carried out. The experiences and results from these were collected and compiled together with the knowledge produced in the project's own investigations and experiments.

Guidelines and communication
The project's scientific results were compiled into practical and simple guidelines for the construction industry, when considering the internal post-insulation of brickwork worthy of preservation. The results, including the collected other Danish experiences as well as knowledge about interior post-insulation, are disseminated together with the guidelines for the Danish construction industry in a more simple format.

The project's results have provided insight into when there may be a risk of moisture-related problems, such as the risk of mold growth with interior post-insulation. The risk depends on the type of wall, orientation of the facade, the indoor moisture load and the insulation system.

The results have not only been published in scientific papers, but they have also been designed as practical and simple guidelines that the construction industry can use when considering whether interior insulation is a moisture-proof way to post-insulate masonry worthy of preservation. These guidelines are in Danish and they are collected on a website together with relevant information on e.g. insulation systems and results from several Danish case studies in a more user-friendly way than in scientific papers. In addition, the project's results have been used as input for the text and recommendations in the section on post-insulation in the new SBi Guideline on "Materials for thermal insulation".

Although the project has come a long way and filled a large number of knowledge gaps, which has enabled the formulation of the practical guidelines, there is still a need for knowledge and research in the subject. An example of additional knowledge needed is determination of the technical moisture limits for mold growth for the materials involved, as the assessment of the real risk depends on these limits.