- THE MAGAZINE
There are five things I do with my inspection kit that most restorers don’t think of doing. Put these into practice and you’ll have a better understanding of what’s going on during your restorative drying projects. Also, you’ll get more for your money out of your current meters.
No. 1: Measure Surface Temperature to Evaluate Energy for DryingMany times on drying jobs, we find ourselves dealing with hard-to-dry materials; a plaster wall or a stubborn subfloor, for example. One of the best ways to help these materials dry faster is to raise their temperature. This increases the vapor pressure of moisture in the material and forces the water out faster.
The easiest way to evaluate the temperature increase is to use a handheld laser thermometer. It’s the simplest way to know how warm a surface is. Simply “point and shoot” and you can find the temperature of that surface. Another approach is to use surface temperature sensors that come with many handheld moisture meters.
During winter especially, drying subfloors over crawlspaces can be a challenge because of cold temperatures below. Using a surface temperature sensor will let you know how much of a problem you will have.
Two things you should know to use your temperature readings effectively:
- Any surface near or below the dew point temperature of the air in your drying environment will make little to no progress (in fact, the material may get wetter!), and
- Increasing surface temperature by only 20° F doubles the pressure associated with moisture in the material and will effectively reduce drying time.
No. 2: Determine the Actual Airflow of a BlowerDid you know that whenever the airflow of a blower is restricted, it actually loses airflow? Seems kind of elementary, but quite often, restorers will hook up ducting, mat systems, or other devices, and expect the blower to achieve the same airflow as it would if it were unrestricted.
If you are in a situation where you need to know the actual airflow of a blower, the tool to use is an anemometer. Simply hook up all the ducting and measure either the input or the output of the blower. Then, use a little math to find the airflow.
First, measure the size of the intake or output of the blower and convert it to square feet. Then measure the feet per minute (fpm) of airflow going into (or out of) the blower. Multiply the two, and you know airflow in cubic feet per minute (cfm).
For example: I measured the output size of an inter-air dryer as 1.5” (.125 feet). The output is circular, so my formula will be:
pi (3.14) x Radius (half the diameter) x Radius again (or, ( r2))
Put into numbers, the formula would look like this:
3.14 x .0625 x .0625 = 0.012 ft².
(Now, don’t you feel smart!)
No. 3: See if Concrete is Dry Under Commercial CarpetMany times in commercial structures, restorers are drying glue-down carpet over concrete. Many restorers simply measure the carpet with moisture sensors, and when they stop beeping, assume that the carpet and concrete are dry. This is a very dangerous assumption.
A better way to measure the concrete through the glue-down carpet is to simply use a non-invasive moisture meter. Set the meter on its most sensitive setting and test several areas. Document these readings on a daily basis and, when they reach dry standard, the concrete is dry enough to call that part of the job “done.”
Warnings and cautions: Beware that carpet in traffic lanes is crushed down and will read higher on the non-invasive meter. Also, beware of concrete that was wet for several days before the drying process started. Concrete in this state can take quite a while to dry, so this test may not be effective in these cases.
Yet another way to measure moisture in concrete, even through carpeting (as long as it is permeable), is to use your thermo-hygrometer. Simply place your thermo-hygrometer on the carpet above the concrete, then place a small section of clear, non-permeable plastic over the thermo-hygrometer. Tape the edges using a painter’s tape, and let the air and hygrometer acclimate with the concrete. This may take anywhere from several minutes up to a couple of hours. The reading is acclimated when the relative humidity on your hygrometer stops changing in a 15-minute period.
Target a relative humidity of less than 80 percent. Pretty simple. You can learn more about using a hygrometer to measure concrete at www.ASTM.org. Check out their test method F2170 for full details.
No. 4: Prove That Heat and Air Exchange Drying is Actually Removing Water From the AirHeat and air exchange drying is a useful tool in restorative drying, especially when there is cool, dry air available outside. One of the hard things about using this method of drying, though, is that many customers can’t understand where the water from their flooded structure is going. On a traditional dehumidifier, the water can be seen pumping out of dehumidifiers, but this water can’t be seen with heat and air exchange systems.
Don’t simply say, “The water is blowing out the window.” This may not be enough information for some customers. Instead, be ready with a tangible number that the customer can understand. Be ready to report the number of gallons removed in a day.
In order to know the number of gallons removed, you need three pieces of information:
- How many cubic feet of air are blowing out of the structure per minute (CFM). Use the CFM of the airmover as a rough estimate, or use Idea No. 2 above to know how much air is moving.
- The GPP inside the structure.
- The GPP outside the structure.
(CFM x Grain Depression)/568 = gallons per day
(If you’re wondering where the number “568” comes from, there is a long discussion in my article “Double the Performance of Your Dehumidifier” published in December 2006, available online at www.icsmag.com.)
For example, if we were ducting an indirect fired furnace into a structure to dry it, and the following factors were measured:
- Outside GPP is 15
- Inside GPP is 37
- Air mover blowing out the window is pushing 1300 CFM
No. 5: Measure an Effective Extraction with a Moisture SensorAhh, my much maligned moisture sensor; you once were the only meter I used to know if a structure is dry. But for the past decade or so, we’ve been saying you’re not good enough to come out of the truck, except on the emergency service of a water loss (and to find urine stains, but I won’t bring that up...).
I’ve recently realized that there is another use for the moisture sensor. When performing “in place” drying, it’s nice to be able to prove that the carpet and pad has dried within the first 24 hours of the job. This shows that the crew performing the deep extraction did their job correctly. It proves that the money you charged for deep extraction was worth it. Most importantly, it proves that vital progress is being made in the drydown.
The readings from a moisture sensor can be a little confusing on the second day of the job, though. When you touch the top of the carpet, it never “beeps.” But if you plunge it too hard into the carpet and pad, it always seems to “beep.” The reason for this is that the pins are touching the wet subfloor, and subfloor rarely dries in the first 24 hours.
So how do I know if the carpet and pad is dry? I simply plunge the moisture sensor into the carpet and pad, listen for the “beep”, and then stop pressing down. When I release pressure, the pins normally stop touching the wet subfloor. If the “beeping” stops, then I know that that spot of carpet and pad is dry.