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 for understanding plant transpiration and human comfort in indoor environments.

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 water vapor pressure and the saturation water vapor pressure at a particular temperature.

3. Importance of VPD Calculation

Details: VPD is crucial for maintaining optimal growing conditions for plants, managing indoor air quality, and ensuring human comfort in controlled environments.

4. Using the Calculator

Tips: Enter saturation vapor pressure in kPa and relative humidity in percentage (0-100%). All values must be valid (SVP > 0, RH between 0-100).

5. Frequently Asked Questions (FAQ)

Q1: What is a good VPD range for indoor plants?
A: Most plants thrive in VPD ranges between 0.8-1.2 kPa, though optimal ranges vary by plant species and growth stage.

Q2: How does VPD affect human comfort?
A: High VPD can cause dry skin and respiratory discomfort, while low VPD can feel muggy and promote mold growth.

Q3: How is SVP determined?
A: SVP is temperature-dependent and can be calculated from temperature or found in standard tables.

Q4: What's the difference between VPD and relative humidity?
A: While RH measures current moisture relative to maximum at a given temperature, VPD measures the actual "drying power" of the air.

Q5: When is VPD most important to monitor?
A: VPD is particularly important in controlled environments like greenhouses, grow rooms, and HVAC systems.