LIVE Wall dehydration monitoring project
The purpose of the project
The purpose of this project is two-fold:
- To test the efficiency of the Aquapol masonry dehydration system in drying out walls affected by rising and penetrating damp
- To gain insight into the fine details of wall dehydration, to better understand how moisture moves inside the masonry
The Aquapol system is a relatively new product on the UK marketplace and keeps generating a lot of interest. Because its technical nature it also generates some skepticism.
We felt the best way to address all questions is by thorough, transparent scientific research done by third party building professionals.
The selected test building(s) are typical British buildings exposed to the British climate, and the measurements are done by British professionals and architects.
What we expect - How do we measure success?
We measure the success or efficiency of the dehydration against several criteria:
- Long(er) term trends: buildings do not dry out overnight, the dehydration of the wall fabric takes time. Comparing seasonal readings from one year to the next gives us a good indication about the moisture situation inside the walls.
- Changes to absolute humidity: absolute humidity is a measure of moisture content independent of temperature. The wall sensors measure relative humidity, which is affected by temperature and atmospheric pressure. Before winter, when temperatures are declining, relative humidity (RH) goes up. Cold air occupies less volume and as a result can hold less moisture, resulting in more condensation and higher moisture readings as temperatures decline. The opposite happens after winter: warmer air expands and relative humidity decreases. By transforming relative humidity into absolute humidity (not affected by temperature fluctuations) will give us good insight whether humidity inside the walls decrease or not.
- Gravimetric measurements: as part of our standard measurement protocol, we measure the moisture content of the walls from drilled samples. We expect our drilled measurements to be in-line with the trends captured by the embedded micro-sensors.
The Building and the Sensors
The test building is a 200 year old countryside British stone building. One wall has been visually affected by rising damp and the owners have agreed to participate in the research project.
The dehydration of the walls is monitored through 4 sets of micro-sensors embedded 200 mm deep into the wall core inside "the rising damp zone" at the following heights:
- Sensor 1: @ 340 mm height, embedded in stone (red line)
- Sensor 2: @ 565 mm height, embedded in mortar (orange line)
- Sensor 3: @ 1090 mm height, embedded in mortar (blue line)
- Sensor 4: @ 1400 mm height, embedded in mortar (green line)
The indoor and outdoor climate is also monitored, sensors are collecting temperature, relative humidity and magnetic field intensity readings 24/7.
Before starting the project, gravimetric measurements (moisture readings taken from the core of the wall using drilled power samples and a drying oven) have been taken from the rising damp zone, which have resulted in moisture content of 10.3 - 1.5% between the highest and lowest measurement point. Gravimetric measurements will be taken every few months to further track the progress of the dehydration.
Please see some images about the project below.
Summary of Changes
21 July 2016
START of the project. All sensors have been installed today. No Aquapol system is being installed yet. We are collecting data to understand how damp the walls are.
6 September 2016 [Aquapol system installed - Day 0]
47 days (almost 7 weeks) later the Aquapol system has been installed. An interesting finding: the magnetic field sensor instantly picked up a change; there was a drop of 1.5 microtesla in the intensity of the magnetic field along the X-axis.
30 September 2016 [Day 24]
24 days after the installation the 2nd bottom sensor (orange) registered a sudden drop. But just a few days before that the upper sensor (green) went up, breaking away from its usual trend. This indicates that the upper part of the wall got damper then shortly thereafter the lower part of the wall started to get drier. This indicates moisture movement inside the wall, possibly water vapors moving upwards from the lower areas of the wall towards the top.
4 October 2016 [Day 28]
There was a storm with heavy rain and lightning over the weekend which possibly affected the upper sensor; it started malfunctioning so it had to be replaced. The humidity inside the sensor hole has dropped to the level of the ambient humidity. After the installation of the new sensor the humidity started building up again.
10 October 2016 [Day 34]
Despite of the relatively nice weather this autumn, temperatures started to plummet and the wall temperatures have dropped to near 14 °C, the lowest they have been since the beginning of the project.
18 December 2016 [Day 104]
There have been over 3 months since the installation of the Aquapol system. During the past few weeks the system went offline on several occasions. One sensor (blue) has been inspected and has been found damp wet with salt deposits on the sensor housing. As a result a decision has been made to replace the sensor housings with a different material to prevent the shorting of the sensors by liquid water.
The sensors and the housings have been replaced on the 14 December, and after sealing the sensors the relative humidity values started climbing again inside the wall.
20 December 2016 [Day 106]
Shortly after the replacement of the housings the blue sensor started heading down, indicating a reduction in moisture. The orange sensor also seems to change direction.
24 December 2016 [Day 110]
In a matter of days the blue sensor had a massive drop, from 100% RH to about 65%.
30 December 2016 [Day 116]
The downtrend continues, another massive drop of the blue sensor, and the orange sensor is now definitely heading down. The red and green sensors also stopped rising and seem to top, indicating a possible change of direction.
3 January 2017 [120 days]
All four sensors now are heading down, indicating that the moisture inside the wall is reducing.