Hygrothermal Performance of Hydrophobized Brick and Mortar: Energy Renovation Through Internal Insulation - Can Hydrophobization Improve the Moisture Safety?

Background: Improving the energy efficiency of the building stock has been an important goal for the European Union for at least 15 years. Given the vast numbers of existing buildings that need to be renovated, efforts towards improving the energy efficiency of these buildings are expected to be increased. Internal insulation of external masonry walls is often the only alternative in existing buildings to maintain the appearance of the facade. However, internal insulation is not considered a moisture safe renovation measure, and wind-driven rain is a main source of moisture to the masonry. Hydrophobization could be a measure to reduce wind-driven rain load on solid masonry facades. Thus, knowledge regarding the application of water repellent agents to such a building facade is required.
Objective: The primary objective of the PhD thesis is to characterize, at the material level, the impact and durability of water repellent agents on building materials used for solid masonry facades: brick and mortar. The secondary objective is to evaluate, at the component level, the impact of water repellent agents on internally insulated solid masonry walls.
Methods & Results: The present PhD thesis is based on three journal articles, in the following referred to as Papers I, II, and III. Papers I and II focus on the material level, paper III on the component level.
Paper I determines the hygric properties of hydrophobized brick and mortar samples. The open porosity and pore size distribution were measured with vacuum saturation
and mercury intrusion testing respectively, revealing only small changes in the storage properties after impregnation. Transport properties in terms of liquid transport were blocked according to capillary water uptake tests. Vapor transport remained almost the same, according to cup tests. Moreover, liquid water impermeability improved after exposure to water as shown by repeating the capillary water uptake tests. In addition, water uptake tests from the non-impregnated side of the samples showed that the water repellent agent is redistributed inside the material after impregnation.
Paper II illustrates that the hydrophobic layer maintains its very low water absorption performance both in brick and mortar, after artificial aging that includes exposure to water and UV radiation. The samples were treated with two different water repellent agents in different concentrations and capillary water uptake tests were performed. Additionally, the findings showed that the absorption coefficient of hydrophobized brick and mortar samples could be further reduced after aging, due to water exposure. Subsequently, Karsten tube tests on artificially aged samples illustrated the same water repellency performance with mock-up walls exposed to ambient conditions