The moisture hood in praxis

Student thesis: Master programme thesis

  • Casper Roland Norling
4. term, Master of Building Physics (Continuing Education Programme (Master))
There are numerous methods for measuring the moisture content in buildings and building materials. However, there are no easy and cheap methods for direct measurements of the moisture content. Furthermore the existing methods have various significant sources of error with respect to the actual determination of moisture content in a given material.
To meet this need for moisture measuring, the moisture hood has been developed. In general, it consists of an enclosed chamber, which is attached to a building material. When equilibrium between the moisture content in the material pores and the moisture content in the chamber is obtained and the moisture content in the pores can be measured.
The main focus in this project was to test the moisture hoods practical application on in existing buildings. This has mainly been on raw concrete walls with various amounts of moisture contents. Furthermore, it was the objective that the “memory” of different building materials should be investigated. Finally different wall coverings and water vapour resistance is discussed.
In this study it is shown that the increase in moisture content in the moisture hood when applied to different building material is rather diverse, mainly due to the condition of the surface. Due to these differences, it has not been possible to complete an algorithm for determination of the final moisture content based on short term measurements. However, a correlation between the first measurement and measurements after 2 hours have shown, that it is possible way to predict the moisture content in the material. This has resulted in a prediction scheme, which is presented in this report.
To illustrate the differences in “memory” as a function of building material, desiccation experiments have been performed. Here it is seen, that bricks have a shorter drying time than concrete tiles. The results also show, that gypsum boards have a longer drying time than bricks. This however, is caused by a much higher initial moisture content in the gypsum board study when compared to the study with bricks and concrete tiles.
Finally it is assessed, that the water vapour resistance of the moisture hood is of subordinate importance when compared to other error sources, such as the condition of the surface and the adhesion between the building material and the moisture hood.
In conclusion, the moisture hood is a fully applicable addition to existing moisture measurement methods, however, further experiments and testing is needed. At present the possibilities for use of the moisture hood needs to be complemented, especially with loggers with internal storage for optimal use.
Publication date1 Jun 2015
Number of pages57
ID: 213396724