Temperature and humidity measurements were made with an Accurite indoor-outdoor thermomenter positioned some distance from our dehumidifier.

The first task was to determine whether the dehumidifier placed at one location in the crawl space corrected the humidity in a different location. After running our dehumidifier about 10 days, I made temperature and humidity measurements with the door fan off and the dehumidifier set for about 45%. Front location: 73°/38%, rear location 75°/43%, dehumidifier console display 70°/42%.

Next I monitored our crawl space for 13 days with the dehumidifier off and recorded humidity each day at 8am and 5pm. I began with the door fans off, then switched them on. The results are shown below.

The measurements suggest that little moisture was coming from the ground, since humidity was constant most evenings when the fan in the A/C was not operating. During the day, however, the fans in the A/C system drew in outside air from the furnace vent and air from the upstairs air returns. When the door fans were turned on continuously, there was a significant humidity increase. As a result we are using our dehumidifier and have turned the door fans off during the summer.

Humidity August-September 2022)