Using Technology to Tackle Moisture Problems
May 18, 2011
Nobody would worry about moisture in buildings were it not for the multitude of moisture-related problems, one of which is mold growth. Mold not only releases toxic particles into the air, mold actually “eats” building materials.
The microorganism extracts the carbons out of building materials and uses them as nutrients to live; dry rot is a prime example of mold’s destructive capabilities. Like all living organisms, mold needs nutrients, air and moisture. All three ingredients are readily available in the building envelope. Of the three, people can most effectively control moisture.
Where's All This Moisture Coming From?Many building materials contain moisture. They are hygroscopic, absorbing or releasing moisture until equilibrium with the surrounding air has been reached.
A newly constructed building already comes with a lot of extra moisture built-in, and drying continues even after the building is finished. Construction lumber installed at 19% will dry down, concrete slabs are still curing, the drywall could have too much moisture picked up during storage and transportation. During the first year a building is supposed to lose its extra moisture, and ventilation is necessary for a healthy start.
Many moisture problems develop later on. Ground moisture could creep into the foundation and adjacent walls. Leaks from roofs or badly installed windows are another source of moisture problems. Floods and other disasters can catastrophically affect a building. Speedy drying-out after water intrusions is essential to avoid additional problems.
Condensation is another dreaded source of moisture problems, as it’s often hidden in the structure and can cause considerable damage. Condensation occurs when warm air reaches cold surfaces. Buildings in climates that require heating in the winter are more likely to develop condensation problems, as heated air from the inside infiltrates wall cavities and condensates on colder exterior materials. For example, damage from condensate is often seen on windowsills. In severe cases the framing lumber and the siding around windows are also affected.
When high moisture is allowed to remain inside a building, problems are unavoidable. Unfortunately, moisture problems often start where nobody can see them: behind walls, below carpets, etc. Noticeable signs are buckling hardwood floors, lifting of linoleum floors, dry rot in wood, musty smells or mold growing on walls. Sometimes there will be complaints about lung irritation and unexplainable coughing. For successful repairs, the source of the problem has to be identified and eliminated. Otherwise, the same problems will come back. Handheld moisture meters and Thermo-Hygrometers are the instruments to use when tracking moisture problems. Pinless and pin meters are available to measure the moisture content in wood, sheetrock and other building materials. Accessories for pin meters allow for penetration deep into walls to locate problem areas. Thermo-Hygrometers can measure relative humidity and temperature; high humidity levels usually indicate a moisture source is close by.
The latest generation of moisture monitoring equipment has the capability to record relative humidity and temperature or moisture content of wood, sheetrock, concrete and other building materials at intervals anywhere between 30 seconds and 24 hours. LEDs indicate when preset min/max limits are exceeded. These devices are designed to monitor crawlspaces, attics and other critical areas where moisture problems are suspected or leaks have been fixed.
Some systems use multi-function wireless transmitters. The measurements from all transmitters in a test area are sent to a central collection hub. The hub collects the data in pre-set time intervals. On-site data retrieval is possible by connecting a PC and downloading the information. Remote Web-based data retrieval is possible using cellular, Wi-Fi or Ethernet technology.
Following is an example of two moisture problems in a residence. A handheld moisture meter and a wireless monitoring system were employed.
The monitoring system consisted of three transmitters and one collection hub. One transmitter was installed outside under the roof to record the outside relative humidity and temperature. The other two were mounted inside. The collection hub was placed in a cabinet in the upstairs living room. All readings were sent via cellular connection to a Web browser.
Two problems were identified: Water was dripping from a leak in the roof into a window frame in the upstairs living room, discoloring the paint and living puddles on the window sill. A musty smell in the basement was constantly present, but there were not yet any visible signs of mold.
The leak in the roof was fixed. One transmitter was installed inside the window frame to monitor the moisture content of the wood and to see if the leak repair was successful. More research was necessary to find the source of the musty smell in the basement. Possible intrusion points for the extra moisture included the foundation and the outside walls, which were partially under ground level. At first, a handheld meter was used to obtain moisture measurements from the sheetrock walls. Readings taken from the sheetrock on an inside wall close to the floor showed 0.7%. In the opposite corner, moisture readings were over 2%. A series of readings was taken along all walls from the floor to the ceiling. Walls not facing outside showed acceptable values for sheetrock. All readings on the outside walls from 3 feet above the floor to the ceiling were in the normal range. Mapping readings from the 3-foot level down to the floor clearly indicated that the greatest moisture concentration was at the base of the two walls facing the outside. The carpet was also measured with the same meter: readings showed the moisture increased toward the two outside walls. To see if any changes in the high moisture levels occurred, the third transmitter was installed in the wettest corner of the room. The transmitter measured the relative humidity and the temperature, the moisture content of the drywall and the surface temperature. Moisture readings in the drywall stayed at a constant high level for months; relative humidity readings in the wet corner were always between 80%-90% and did not change much, even during the summer. The structure and the ground around the building had soaked up too much moisture during the wet winter. Proper drainage needed to be installed around the building, and the outside walls needed to be sealed to prohibit moisture migration. Then the basement could be dried out successfully and hopefully will stay dry. To preserve the health of a building and of the people living inside, moisture problems need to be addressed as soon as they are noticed. It does not help – and in fact, only exacerbates – the problem to cover it with paint, install a new floor or perform any number of cosmetic fixes if the source of the excess moisture has not been removed.