Water content measurement in building barriers and materials using surface TDR probe

Water contained in external walls is one of the the basic factors restricting the functioning of buildings. Its negative influence should be evaluated both in the constructional and hygienic aspects. It is caused by the fact that water is not only the reason of successive destruction of buildings' construction, but also composes the base for the growth of microorganisms and moulds. Such problem is typical for the buildings without moisture control and monitoring and causes the respiratory system illnesses, infections, allergies, eyes and skin sensitisations. The buildings affected by the problem of moisture in most cases are stricken with the Sick Building Syndrome, which is caused by the use of not human-friendly materials, defective ventilation or high moisture previously mentioned. Water contained in the external walls significantly diminishes their thermal characteristics, which induces the increased heat losses in cold season, reduction of perceptible temperature and thermal comfort of accommodations. All the previously mentioned negative aspects of water influence on the buildings cause the need to find the precise, user-friendly method of water content valuation in the walls. One of them is TDR (Time Domain Reflectometry). This technique bases on the measurement of the electromagnetic pulse propagation in examined medium. The dielectric constant of the material (determined with the TDR device) is the base for its moisture estimation. The TDR method has got a lot of advantages (high monitoring potential, insensitivity to the salinity, relatively simple service) and has been used in moisture measurements of porous materials, especially of the soils, for many years. By now, this technique has not found the common implementation in the building area which is caused by its invasive character - it requires the installation of the steel rods in the examined medium, which sets many problems in case of building materials and envelopes. The aim of this paper is to propose the alternative idea of the TDR probe - surface probe, which enables the moisture measurements of hard building materials and envelopes. For these materials, the use of classical probe is difficult to realize, because of problems with the introduction of the steel rods in the examined medium. This, modified, TDR method enables the effective moisture measurements without the need to destroy the building barriers structure.