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Vapor Pressure Deficit Calculator

The VPD can be a valuable metric for growers to predict water use.

The VPD can be a valuable metric for growers to predict water use.
The VPD can be a valuable metric for growers to predict water use.

Dr. Greenhouse, a provider of HVAC design and controls solutions for indoor grows, vertical farms and greenhouses, has launched the Dr. Greenhouse VPD Calculator App. The VPD Calculator app helps growers understand their indoor grow environment and its effect on plant responses and HVAC equipment operation.

“Our website VPD calculator is the most visited resource on our website. Our team decided to build a mobile VPD Calculator App for growers and farmers to quickly calculate their environment’s VPD,” notes Dr. Nadia Sabeh, President of Dr. Greenhouse, Inc. “It is critical to know the best environment for plant steering and health to ensure optimal crop outcomes and timing are achieved.”

Vapor pressure deficit (VPD) represents the “pressure” that air puts on the plant to transpire and move water and nutrients from the roots to other parts of the plant. For example:

  • With low humidity and high VPD levels, there is more pressure on the plant to transpire and use more water. If plants are not well-watered under high VPD levels, they may begin to wilt.
  • With low humidity and low VPD levels, there will be less pressure on the plant to transpire. If plants are over-watered under low VPD levels, they are prone to pest pressures.

The VPD can be a valuable metric for growers to predict water use, steer crops for optimal growth, and operate HVAC equipment to achieve the desired indoor plant environment.

The Dr. Greenhouse VPD Calculator App supports all crop types and includes VPD lookup tables for tomatoes, leafy greens, and cannabis. The VPD Calculator App allows growers to use their existing air temperature and humidity sensors to understand if the room condition is more suitable for vegetative, flowering, or stress-induced plants. The VPD Calculator App provides color-coded results to indicate if the room is humid (blue), vegetative (green) or reproductive (yellow), or dry (purple).

For facility designers and grow house managers, the VPD Calculator App can predict evapotranspiration rates to estimate plants’ water usage and dehumidification requirements. With this information, the HVAC equipment can be designed to meet facility climate control goals.

Sabeh comments on VPD, crop production, and facility HVAC design, “When the right VPD is targeted for a given crop, variables such as light source, nutrients, water, HVAC and dehumidification can be controlled to minimize operating costs while maximizing plant growth and health.”

The Dr. Greenhouse VPD Calculator is free to download in Apple’s App Store and Google Play Store.

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