ELECTROPHYSICAL DEHUMIDIFICATION OF MASONRY

 

While in nature humidity plays an essential role for the growth and sustenance of life, if in excess, for instance in buildings, it may be noxious and cause severe damage. In fact, damage to plaster, salt efflorescence, stains and mold in the masonry of underground and groundfloors are often the result of the so-called rising damp inside walls.

The crypt of the Cathedral of Our Lady of the Assumption in Cremona was affected by extensive damage caused by rising damp. The bishop of Cremona decided to choose among various methods available in the market the most convenient solution to counter the problem in such a wide a complex. Any mechanical interventions  implying that the wall masonry bottom would be removed and replaced with materials capable of preventing damp from rising were discarded, as this method is likely to cause the structure to get damaged, or even collapse or settle. Similarly, a chemical method whereby hydrophobizing substances are injected into the masonry to create a chemical barrier was rejected too, because the intervention, with several bores being drilled, would be too invasive. The crypt walls are made of marble, which excluded the chance of using any macroporous plasters, which feature high speed of evaporation and can rapidly absorb water from a wall and disperse it into the air. However, while capable of temporarily solving the symptoms of moisture, this method will not eradicate the problem.

In February 2013, the bishop of Cremona resolved to install Genié, a solution based on the innovative electrophysical dehumidification technology using “multiple frequency impulses”.
A study conducted by Luigi Soroldoni (scientific advisor for cultural heritage and professor at “Aldo Galli“ Academy in Como) and Umberto Casellato (former Associate Head of Research with IDPA – CNR) demonstrated that the problem was eventually solved. After  12 months from the installation, moisture in the walls fell heavily, by as much as 70% in some cases; after 16 months, the dehumidification process brought the rate of humidity of masonry down to a range between 2% and 4% (physiological rate in masonry).

How Genié works
Genié generates an electromagnetic field inside the masonry, which interacts with the water molecules and prevents them from rising. Unlike other methods, which use monofrequency, Genié generates a train of impulses at different frequencies allowing to obtain guaranteed results on all types of masonry, regardless of the shape of their capillary pores and of their composition. Genié is installed by fixing it with four standard screw dowels and connecting it to a standard socket.

1_Because water molecules are bipolar, they are attracted by electric forces into microscopic canals, also known as capillary pores.
2_Each molecule found in the ground can therefore migrate upwards through the capillary pores of the foundations into the walls of a building.
3_During its rise, water dissolves and carries with it any salts met on the way, which in turn are one of the main causes of plaster degradation.
4_The rise stops along a “0 potential” line, where capillary adhesion and gravity get balanced.
5_Here, the water found in the walls evaporates, it is released in the environment and replaced by more water rising from the ground.
6_Genié generates impulses capable of disturbing the electric forces of adhesion inside the capillary pores of walls.

With a constant and targeted work, the installation brings the “0 potential” line down, by pushing water back into the ground. This helps stop mold and avert all risk of masonry degradation.
After the walls are rehabilitated, they can be brought back to their original state, with no further risks of plaster damage, salt efflorescence, stains, mold, etc.
Genié is totally safe and can be used in any living environment, even with children, old people or sick people. In fact, Genié generates an electromagnetic field inside the masonry, which does not interfere with human beings or with any electric or electronic appliances of sorts, including medical and sanitary apparels.

Method of study of the efficiency of the dehumidification method
Sampling was performed through measurements of the humidity (free water) content with the thermo-gravimetric method, by calculating the weight balance after water was eliminated by forced evaporation.
Two samples of 3-5 g were collected in each examined area, by using a core-drill (18-20 mm wide), of which one at a depth of 0-10 mm and one at a depth of 50-150 mm, at floor level and at about 1.5 m above the floor, respectively.
The samples were weighed with precision scales (sensitivity of 1 mg), stored in special glass containers and then put in a heater under controlled temperature (105° C) until they reached a constant weight.
The balance between the initial weight and the post-drying weight expressed as a rate of the dry material represents the value of humidity found in the sample.
To allow any future measurements after the dehumidification process or any further assessments, the wall was plugged with some specially conceived small cotto bricks, whose water absorption capacity is similar to the old bricks, so that they may be removed with no need for further core-drilling.

Humidity measurements
In February 2013, before dehumidification works, the wall showed visible damage from rising damp, and namely portions of plaster lifting and peeling off, and powdering of the painted layers, which are all the result of water movements and, above all, of the exchanges with the inner environment during evaporation and condensation.
The measurements proved that moisture was present along the north wall, with particularly high rates at floor level, both superficially and deep into the masonry (10-16%).
At about 1,5 m above the floor, the rate of humidity was normal for an underground environment (3-5% in areas A and B), but the rate grew inside the area C (14.%). The north wall too at floor level featured high rates of humidity deeper into the masonry (8-9%)and even at 1,5 m above the floor in the area E (8%).
After seven months of operation of Genié devices (1 device + 1 satellite installed on the south and on the north wall, respectively) a general reduction in moisture was remarked, with 30-40% falls in the dampest areas, both at floor level and at 1.5 m above the floor.
After one year, the walls looked positively drier, with a remarkable fall in rates (70%), which reached the normal humidity levels of masonry. Some humidity (10-16%) was still found in two out of 12 spots on the north wall.
After 16 months, the rates have stabilized at values of physiological humidity, except in the area A, which still features some humidity both inside the masonry (12%) and on the surface (8-9%). This may be due to microclimatic conditions and to the heavy content in salts of this portion of masonry.

Conclusion
To conclude, after the installation of Genié devices, the conditions inside the crypt improved sizably in general terms. The current stable conditions are confirmed by microclimatic data, which show that the north wall is cooler especially during winter, but is generally more prone to interstitial condensation in May and June, resulting in increased humidity inside the masonry.
This sensitivity to interstitial condensation and the salt content are therefore the reason why moisture remains high in the area A, which will require a targeted intervention aimed at removing the salts.

 

[by Luigi Soroldoni, Scientific consultant for Cultural Heritage and Professor at the Academy "Aldo Galli" in Como, e Umberto Casellato, Former associated research director at IDPA-CNR]