By W. Douglas Webb
Many facility managers know basic steps they can take to protect their business from invading pests, such as keeping doors and windows closed and properly weatherized, cleaning common spaces, and communicating regularly with employees. But a common source of pest management challenges – moisture control – can prove elusive to even the most seasoned pest preventing facility manager.
Take the following quiz to put your moisture control knowledge to the test.
1. What are sources of moisture inside facilities that pests can use for survival?
a. Condensation inside walls
b. Soil moisture in a crawlspace
c. Plumbing leaks
d. Rain wetting
e. All of the above
2. Insects need a constant supply of fresh, flowing water to survive inside a structure, such as a plumbing leak.
Answer: False. Most insects can easily get the water they need from condensate on surfaces and some can get it from elevated moisture in wood.
3. Moisture problems in buildings can contribute to which of the following?
a. Insect infestations
b. Increased energy cost to operate HVAC systems
c. Discomfort to occupants
d. Answers a and b only
e. Answers a, b, and c
4. Which of the following is not one of the three states of water?
Answer: d. Mist consists of tiny droplets of liquid water, so it is still in the liquid state.
5. What happens when moist air meets any surface that is cooler than it is?
a. Evaporation occurs
b. Condensation occurs
c. Nothing happens.
d. Answers a and b above
6. Wood swells when in the presence of:
a. Liquid water
b. Water vapor
c. Lowered relative humidity
d. Wood does not swell once it is installed in a building.
e. Answers a and b above
7. In general, the moisture content of wood in a properly maintained, air conditioned structure during the summer in most areas of the United States is about:
8. Wood only swells when the moisture content (MC) changes from:
e. Answers a, b and c above
Answer: e. Wood swells from its bone dry state at 0% MC up to its saturation point which is around 26-28% MC for most species of wood. At 30 % or above, the wood fibers are saturated which means they cannot hold any more water and thus cannot get any larger by swelling.
9. Wood that is constantly in an environment with 80% relative humidity will always have a moisture content of:
Answer: b. Wood is a very consistent material and the moisture that is contained in the wood is directly relative to the moisture in the surrounding air.
10. If a 20-foot wide room with a wood floor has a problem with its air conditioning and changes from 30% relative humidity to 65% relative humidity for a few weeks, the floor will swell a total of ___ across its width.
a. 1/2 inch
b. 1 inch
c. 6 inches
d. 12 inches
Answer: c. If the relative humidity is 30%, the moisture content of the wood in the floor will be 6% and when it is 65%, the moisture content will be 12%. This is a 6% change. Between 0 and 28% moisture content, any change in the moisture content of wood of 6% (up or down) will result in a 2.5% change in its tangential plane (width of a board). 2.5% of 20 feet is 6 inches! This can cause floors to buckle when moisture goes up causing the wood to swell, or gaps to open between flooring boards when they shrink as moisture goes down.
Webb is technical services manager with Terminix International. He obtained his Master of Science degree in Wood Science and Technology from Mississippi State University, having specialized in Wood Destroying Insects and Wood Deterioration. He has served Terminix customers across the United States for over 35 years.