What Is a Psychrometric Chart in Water Damage Drying?

A psychrometric chart plots air properties on a graph. The horizontal axis shows dry bulb temperature, which is the regular air temperature you feel. The vertical axis shows humidity ratio, or the actual weight of water vapor in the air. Curved lines represent relative humidity, and diagonal lines show wet bulb temperature.

Pros use these readings to understand the air's capacity to hold moisture. Warm air holds more water vapor than cool air. When the chart shows low relative humidity and warm temperatures, the air can absorb more moisture from wet materials. When conditions are humid or cool, drying slows down.

• Dry bulb temperature: the air's actual temperature
• Wet bulb temperature: reflects evaporation cooling
• Relative humidity: percentage of moisture in the air
• Humidity ratio: actual water vapor weight
• Dew point: temperature where condensation forms

Pros take readings at several points in the drying area. They measure air temperature, relative humidity, and sometimes surface temperatures of wet materials. These numbers get plotted on the psychrometric chart to show the current drying conditions.

They also compare readings from different locations. A crawl space might have different conditions than an open living room. By mapping these variations, pros can decide where to place drying equipment for the right effect.

A psychrometric chart is a tool that shows air conditions, but it does not measure moisture inside walls or under flooring. Pros still need moisture meters and visual inspections to confirm drying progress. The chart helps guide the work, yet it does not control the outcome.

The chart works well when combined with regular monitoring. Conditions change as drying proceeds, so pros take new readings periodically and update their analysis. This ongoing check helps them adjust equipment as needed.