ELECTRO-PHYSICAL DEHUMIDIFICATION

“La Sapienza” University in Rome

  

Designed by the Rationalist architect Giovanni Michelucci in 1932 and inaugurated along with other buildings inside the university campus of Roma La Sapienza in 1935, the edifice is an example of Italian Rationalist architecture with its neat reinforced concrete skeleton and travertine stone facade.
Located in the neighbourhood of San Lorenzo, near the strategic railway stations of Roma Termini and Tiburtina, the university campus is one of the most important achievements of Italian Rationalism, whose site management and coordination was entrusted to Roman architect and town planner Marcello Piacentini. A monumental gate overlooks the main square, Piazzale della Minerva, where the severe front of the Rector’s Palace stands out, the work of Piacentini himself. The north and south ends of the square accommodate the building of the Department of Earth Sciences designed by Michelucci and the building of the Department of Mathematics designed by Gi. Ponti, respectively. Both edifices have their fa.ades lined with travertine stone slabs and abide by the traditional nationalist and rationalist aesthetic rules dictated by architect Piacentini.
The main front of the Department of Earth Sciences is simple, neat and symmetrical, with two staircases to the sides giving access to the main entrances, raised on platforms and scooped deep into the facade. Deep loggias in the two top floors create two peculiar side zones contributing light and shadow effects to the facade. The central portion is characterized by four rows of windows, three of which are rectangular in shape and the top one has smaller horizontal openings. A delicate moulding outlines the whole volume on top the complex is composed of two buildings. One faces the main square and has a traditional plan with a rectangular central courtyard; it rises on three above-ground levels and one basement level. The interiors accommodate all the areas dedicated to students and teachers, including conference halls, classrooms, the library, etc. Another volume stems from the north-eastern corner of the former building and has a tapered rectangular plan to house the mineralogy and geology museums. An L-shaped corridor connects the two building creating an inner courtyard.
In 2015 some degradation was remarked in the basement masonry, where the archives are located, caused by humidity, and namely by water rising from the underground. This particular phenomenon is owed to the typical polarity of water molecules, capable of interacting with the stone of the masonry, which is equally polar and therefore hydrophilic. Electrical forces cause water to become attracted into the micro-pores (capillaries) of masonry and, by adhesion, to migrate upwards and transport all salts encountered while rising. The problem affects walls and relevant finishes up to 1.5m; rising stops when capillary adhesion cannot counter the gravity force. The prominent degradation of the masonry, mainly caused by salts, consists in plaster peeling off and swelling copiously, with a resulting loss of material. Moreover, the water trapped inside the walls evaporates into the rooms and interferes with the health of the environment, as well as with the conservation of the books in the archives. Finally, any humid masonry is potentially at risk of biological attack.
For all the reasons above, the University management decided to solve the problem of rising damp prior to restore wall finishes. The operation is necessarily preliminary to the renovation of the plasters; otherwise the plasters, while new and more macroporous than the old ones, would degrade soon. First of all, the management entrusted Tecnova Group to supply an electro-physical dehumidifier, which was installed inside the rooms and connected to the mains. The system helps solve the problem by generating electromagnetic pulses capable of interfering with the electrical interactions of water and masonry. In brief, it prevents capillary adhesion and therefore rising damp, keeping water low in the walls.
Before installing the device, a site analysis was carried out, with the measurement of the amount of water in the walls at different heights. This preliminary fact-finding step was followed by the installation of two dehumidifiers with a range of action of 15 and 10 metres, respectively, in July 2015. During the drying process, the rooms must be ensured adequate ventilation, controlled temperature of 20ÅãC and relative humidity of 65%.
One year after the installation of the system, some masonry samples were collected to monitor the content of humidity in the plaster, with the help of a ponderal analysis and the identification of the salts in the masonry. Small holes of maximum 10mm width and 10cm depth were bored to collect the samples, whose humidity values were measured by means of the ponderal method with thermal-hygrometric verification. The method helps calculate the balance between the weight of the sample at humid state and the weight of the sample after it is dried under controlled temperature not exceeding 110°C.
The results of the analysis above were compared with the data obtained from the ponderal analysis performed upon the installation of the device in July 2015. The diagram of the comparisons show the fall in water content in the masonry. Water content values at different spots vary between 5.9% and 13.8%, therefore exceeding the physiological content of masonry, equal to 2%-4%. This means that the drying process is still at an early step and further analyses will be needed to obtain better results. Once the convenient humidity value in masonry is reached, then the plaster and all degraded finishes will be restored.

[by Giorgio Di Ludovico – text Alessandra Ledda]