Electrical effects in damp masonry, how the movement of humidity in masonry is ALWAYS accompanied by electrical activity was one of recent important discoveries. Whenever a wall fabric gets damp, electrical voltages and currents spring to life in it instantly – humidity and electrical activity being INSEPARABLE.
This statement can be verified easily in practice. Using a simple multimeter on a damp wall reveals the presence of a small voltage (usually under 500 mV) in the wall between the ground and some other damp point higher up the wall. This is a simple way to demonstrate the presence of electrical effects in damp masonry - but there is more to it.
These electrical variations accompanying the presence of moisture in the fabric are resulting from at least 2 sources:
As mentioned earlier, the movement of humidity in masonry is always accompanied by electrical activity. In the presence of humidity, the otherwise non-conductive wall fabric becomes conductive. Different levels of humidity are accompanied by different voltages in the wall fabric, then small currents start flowing in every direction (from higher voltage to lower voltage areas) in an attempt to even out voltage differences.
These electrical potentials appear in damp masonry due to the fluid nature of water. Water is not a static molecule, but a highly dynamic one, consisting of a small H+ part (proton) and a larger OH- part. These parts are in constant interchange, every water molecule breaking up and re-creating itself millions of times per second, the small agile H+ part (proton) jumping back and forth between neighbouring larger OH- molecules. This is known as proton hopping.
When water evaporates, a large amount of small and agile H+ protons jump through the surface, making water vapours positively charged. The slower OH- parts are left behind, making liquid surfaces slightly negative. Thus, evaporation brings about a charge separation in water – this is similar to a pack of runners, where the faster runners end up towards the front of the pack (vapour) while the slower ones stay behind (liquid).
These electrical charges are transferred to the masonry, giving it either a positive and negative charge, depending on whether in a certain area vapours (positive) or liquid moisture (negative) dominates.
During condensation (liquefication), the reverse happens, the positive vapours gradually decrease while the liquid moisture content increases, leading to increased negative charges in the fabric.
In dry masonry electrical activity is non-existent. There is no charge separation, so a completely dry masonry is uncharged (zero or near-zero charge).
The presence of salts significantly increases electrical activity in damp masonry, taking that to a whole new level. This is because:
These electrical parameters can be precisely measured and visualized with appropriate lab instrumentation. Here is some real-life data.
Small voltages up to 1-2 V are generated in damp masonry by the presence of moisture and salts.
At certain vapour/liquid ratios in the wall fabric the interdependence of humidity and electrical voltages can be seen very clearly, voltage variation (lower half) following humidity variations (upper half) very closely.
In the presence of salts voltages can increase significantly (red/purple lines) in comparison to voltages measured in "plain" damp non-salty walls (blue/green lines).
Just as different humidity levels cause pressure variations in the masonry leading to evaporation and condensation flows, electrical voltage differences lead to electrical current flows between various points in an attempt to even-out the electrical variations of the wall fabric.
Just as water vapours flow from higher pressure to lower pressure (higher to lower evaporation) areas, electrical currents flow from higher to lower voltage areas. The presence of salts can increase these currents by 100 to 1,000 times or more, as illustrated below.
Depending on the moisture gradients in damp masonry, electrical currents can flow horizontally and/or vertically, as well as in between bricks and mortar if those are at different humidity levels (which most of the time are). Hence, the “breathing” mechanism of the wall fabric which creates ongoing humidity variations also generates a host of electrical variations in the masonry.
As mentioned earlier, humidity and salts make the wall fabric electrically conductive. This can be quantified by measuring the masonry’s electrical resistance, which decreases when conductivity increases.
While a dry wall fabric’s electrical resistance can be extremely high (close to infinite), the resistance of a damp wall fabric can decrease by about 10,000 – 100,000 times – a very significant change.
In addition to the inter-molecular electrical effects described above, the external electromagnetic (EM) environment is also affecting the movement of moisture as all houses and walls are surrounded by open spaces filled with electromagnetic waves.
The air around us is full of invisible electromagnetic (EM) waves. We are not only surrounded by but literally “swimming” in a sea of energy.
A lot of EM waves surrounding us are man-made. Planetary electromagnetic pollution, due to an exponential increase of wireless communications, have increased from the extremely low natural levels of the 1950s by about 1018 times, increasing by over 10 million times just from the 1980s onward.
We are undergoing an “electromagnetic climate change” which, no doubt, is also affecting to some extent our old buildings and our cultural heritage.
In addition to man-made EM fields, planet Earth has its own natural magnetic field known as Earth’s geomagnetic field. This can also undergo significant variations as a result of its interaction with the Sun and solar wind, resulting in geomagnetic storms, substorms and geomagnetic pulsations.
When wall capillaries are made conductive by humidity and salts, they to a large extent start behaving as regular electrical conductors. When an electrical conductor is subject to changing magnetic fields, that will generate in the conductor an electrical voltage and current. This is known in Physics as the law of electromagnetic induction.
Here are some of the geomagnetic pulsations visualized on a sensitive high-end magnetometer.
These geomagnetic pulsations (orange) – sequences of randomly occurring fast-changing pluses – penetrate the walls, transferring their energy to the wall fabric, generating fast-changing voltages (red) and currents (blue) inside the wall fabric. Although geomagnetic pulsations are relatively small (about 1-2 nano tesla nT), their effect onto the even tinier water molecules (about 0.1 nm) is significant.
The induced currents in the wall fabric, having very sharp fronts, inject their energy into the electrical double layer (EDL), charging-up the capillary surfaces. This increases the electrical double layer’s ability to bond and retain more water molecules than in a less charged state, keeping the masonry damper.
Some of these concepts are discussed in a more interactive format in the video below:
Existing research data suggests that magnetic fields seem to act as a catalyst or an aggravating factor, their action contributing to the wetting of the masonry.
Here is the sequence:
Salts working in conjunction with EM fields are one of the most important variables of the topic of moisture in old buildings. Understanding these phenomena is an integral part of building conservation.
Research of this very interesting field of building sciences is underway, and no doubt it will lead to many interesting findings in the near future, resulting not only in a better understanding of moisture, but also in the development of novel, smarter, less-invasive technologies.
This research line led to the development of the magnetic DPC technology – a novel way of solving rising damp in old buildings in a building-friendly, non-invasive, reversible way.
Here are the some recommended materials / products that can help solving or dealing with some of the problems discussed on this page.
