How to Design an Energy Efficient Greenhouse

Growing in a greenhouse has many benefits. The ability to harness natural sunlight, while still controlling the environment is critical for modern cultivation. But operating a greenhouse is energy intensive, especially when they aren’t designed to be energy efficient.

Designing a greenhouse is complicated, especially an energy efficient greenhouse. There are numerous factors to consider, and most of them affect each other, making the design much more complex. For most new or retrofitted greenhouses, it’s recommended to consult with professionals, to ensure an energetically efficient, profitable operation.

This post breaks down the different factors necessary to building an energy efficient greenhouse.

8 Considerations for an Energy Efficient Greenhouse

These are the main factors to consider for energy efficiency, before designing or retrofitting a greenhouse:

  1. Location and geography

  2. Greenhouse type, size and cover

  3. Crop type and density

  4. Desired greenhouse climate

  5. Thermal screens, shading and blackout screens

  6. Lighting and radiation

  7. Heating and cooling

  8. Humidity control

1. Location and Geography

Before designing a greenhouse it’s important to understand the local climate. Outdoor weather plays a huge role in determining the conditions inside the greenhouse. In order to achieve optimal conditions, it’s critical to know what the starting point is.

The length of day and radiation determine the amount of lighting needed. Temperature and humidity determine the need for heating, cooling and dehumidification.

To make the right decisions in the design stage, it’s best to fully understand local weather patterns, including temperature, humidity, wind and day length.

2. Greenhouse Type, Size and Cover

Greenhouse size determines the necessary capacity of climate control equipment such as HVAC, boilers, or dehumidifiers. The bigger the area, the larger the capacity must be in order to be effective.

The build, cover, materials and type of greenhouse also have an effect on the conditions inside. Different covers will provide different characteristics when it comes to isolation and radiation penetration.

3. Crop Type and Density

The crops inside a greenhouse have a great effect on conditions as well.

First, the plants dictate the conditions you’ll need in your greenhouse. Growing peppers will require different conditions than growing cannabis. Understanding the plants’ needs is at the heart of greenhouse growing.

Second, the plants themselves affect the conditions in the greenhouse. Plants are living beings that constantly interact with their environment. They affect the temperature and humidity in the space and need to be taken into consideration. The amount of plant matter and density (often measured as leaf area index – LAI) play a large role in determining the amount of dehumidification necessary.

4. Desired Greenhouse Climate

Before you start adjusting your greenhouse climate, and in order to make sure you do so efficiently, it’s important to know what your set points are.

The desired climate, including temperature, humidity and lighting must be tailored to the plants in the greenhouse.

Growers must consider their current environment – location, climate, greenhouse size and cover, and understand what climate control equipment is needed to adjust their greenhouse environment accordingly.

5. Thermal Screens, Shading and Blackout Screens

Screens are a critical part of greenhouse growing. Using a combination of thermal, shading or blackout screens drastically increases growers’ control over the environment.

Using thermal screens lets growers trap the warm air inside when necessary, reducing the need for heating. One thermal screen can reduce heat loss by as much as 60%. Combining 2-3 screens can reduce up to 90%.

When using dehumidifiers, thermal screens can be kept closed even longer, while the climate inside the greenhouse remains within ideal range.

Blackout and shading screens give growers greater control over lighting. The length of the day doesn’t always match with the plants’ desired day length. Some plants are very particular about their day-night cycle and require a strict regimen.

Cannabis, for example, requires 8-12 hours of complete darkness in order to grow optimally, depending on cultivar and growth stage.

6. Lighting and Radiation

Supplementary lighting is used to increase radiation, measured as kWh/m2, when there’s insufficient sunlight, as well as to increase the day length.

Using artificial light is crucial in most areas, as days get short and cloudy weather blocks out radiation. So, it’s important to make sure your lights are energetically efficient.

Though HPS lights are as much as 5 times cheaper to install, choosing LED lights can save up to 70% of the energy, making it a smart investment in most greenhouses.

LED lights are more efficient because they emit less heat, utilizing more energy for light. This also helps growers control their greenhouse temperature more efficiently and is especially necessary in warm climates, where greenhouses often require cooling.

7. Heating and Cooling

After considering the conditions, both outside and inside the greenhouse, growers need to determine the amount of heating and/or cooling they’ll need.

There are many methods to heat or cool. From intricate piping systems to HVACs. These methods differ in their capacity, efficiency, infrastructure and cost.

Heating and cooling are some of the biggest sources of energy consumption in greenhouse cultivation. So, tailoring their performance to your greenhouse is critical, both for effectiveness and for efficiency.

8. Humidity Control

One of the least understood factors affecting energy is greenhouse humidity.

Humidity is a major issue in greenhouses. To deal with high humidity, growers turn to one, or a combination of several methods.

The most commonly used method is heating and venting. Growers open the greenhouse in order to release water vapor and decrease humidity. In a heated greenhouse, this requires re-heating, as the heat escapes as well. This is one of the greatest energy consumers in traditional greenhouse growing.

A much more efficient option is using a greenhouse dehumidifier. With dehumidification, growers can keep the greenhouse closed, retaining heat and energy.

Like with temperature, growers should know what relative humidity level their crops desire. They should also be aware of the humidity and temperature outdoors, in order to decide on the best method and equipment for their needs.

The capacity of a dehumidifier needs to match the rate of evaporation, or humidity will continue to rise. Plant density, radiation, temperature and humidity all affect the rate of water evaporation.

At DryGair, we ask potential customers to fill out a questionnaire before purchasing our products. The questionnaire covers all of the factors described in this article. This ensures your dehumidification matches the greenhouse’s needs, in terms of coverage and capacity.

Using the correct equipment for your greenhouse provides the best conditions for the crops and saves energy.

Consult with Professionals to Design an Energy Efficient Greenhouse

Designing an energy efficient greenhouse isn’t a simple task. For most growers, it’s recommended to seek out help from professionals. Expereinced engineers can better understand the intricacies of greenhouse physics and design it optimally, using the right equipment.

Companies like Hortinergy provide energy and climate analysis for greenhouse projects. They do so by collecting data and creating a detailed energy report based on calculations and models.

Energy efficient greenhouse -- Hortinergy

The models can take several scenarios into consideration, providing reports for each. Comparing different greenhouse designs and equipment, before building a new greenhouse or retrofitting existing facilities, lets growers make the best decisions.

Designing a greenhouse or introducing new equipment wisely, based on calculations, makes cultivation much more efficient. Growers can grow with less energy consumption, smaller utility bills and better results.