Internal Insulation of Masonry with and without Hydrophobization in Inhabited Dwellings

A large part of the European buildings were built from 1850 to 1960; a period when there was minimal focus on energy savings. Simultaneously, the facades of many of these buildings are worthy of preservation, so for additional insulation only internal thermal insulation is an option; despite various cases of mold issues in the intersection between the insulation and the wall.

For insulation materials to be generally accepted, they have to be tested in reality to prove their efficiency and moisture safety to ensure the construction's robustness and the inhabitants' well-being. The present paper describes two case studies consisting of two residential building complexes in which the same type of diffusion open insulation material was applied in several apartments.

In one of the cases, internal insulation was applied in combination with and without hydrophobization of the masonry. The performance of the two cases was determined by measurements of temperature and relative humidity at the intersection between insulation and masonry and in the indoor climate. Furthermore, the risk of mold growth was determined.

The project investigated the conditions of the wall in relation to the masonry and insulation thickness, orientation of the wall, the impact of hydrophobization, and internal moisture load. Most measurements showed no risk of critical mold growth since the Mold Index did not exceed 2 in the wall interfaces.

Exception to this appeared to be areas with thin masonry, high insulation thickness, or high indoor moisture load (more than humidity class 2). Surprisingly, the hydrophobization was most effective in the orientation with the least wind-driven rain. Finally, it was shown that a hydrophobized area with higher exposure to runoff faces harsher conditions than the one with high direct wind-driven rain.