1. What is Vapor Pressure Deficit (VPD)?

Vapor Pressure Deficit (VPD) is the difference between the amount of moisture in the air and how much moisture the air can hold when it's saturated. It's an important metric in various fields including agriculture, HVAC, and environmental science.

2. How Does the Calculator Work?

The calculator uses the VPD equation:

Where:

• \( SVP \) — Saturation Vapor Pressure (kPa)
• \( RH \) — Relative Humidity (%)

Explanation: The equation calculates the difference between the actual and potential vapor pressure in the air, which indicates the air's drying potential.

3. Importance of VPD Calculation

Details: VPD is crucial for understanding plant transpiration rates, human comfort levels, and building humidity control. It helps optimize growing conditions in greenhouses and maintain comfortable indoor environments.

4. Using the Calculator

Tips: Enter Saturation Vapor Pressure in kPa and Relative Humidity as a percentage (0-100%). Both values must be valid (SVP > 0, RH between 0-100).

5. Frequently Asked Questions (FAQ)

Q1: What is a typical VPD range for human comfort?
A: For human comfort, VPD typically ranges between 0.5-1.5 kPa, with lower values feeling more humid and higher values feeling drier.

Q2: How does VPD affect plant growth?
A: Plants have optimal VPD ranges (usually 0.8-1.2 kPa) where transpiration and growth are balanced. Too high causes stress, too low limits nutrient uptake.

Q3: How is SVP determined?
A: SVP depends on temperature and can be calculated using the Antoine equation or looked up in standard tables for given temperatures.

Q4: Why use kPa for VPD measurement?
A: kPa (kilopascals) is the SI unit for pressure and provides a standardized measurement that's widely recognized in scientific applications.

Q5: Can VPD be negative?
A: No, VPD cannot be negative as it represents a deficit between actual and potential vapor pressure. RH cannot exceed 100% in normal conditions.