Ideal Greenhouse Temperature And Humidity

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To successfully grow crops in a greenhouse, temperature, and humidity must be controlled. The ideal greenhouse temperature ranges between 64 and 75 ºF, depending on what is being grown. As humidity is directly related to temperature, maintaining an optimal relative humidity level of around 80% is also essential. 

Do you wish you could grow your favorite fruits and vegetables all year round? Growing every type of plant is impossible outside because of temperature changes, but inside a greenhouse, you can grow all your favorites.

Every plant needs moisture, warmth, and light to grow and thrive, which is why a greenhouse makes the perfect growing environment. Inside a greenhouse, you can buffer the ambient temperature and control the humidity levels.

Ideal Temperature For Greenhouses

Whether you are maintaining a healthy garden with a hydroponic system, or you are growing plants in soil, to successfully grow plants/crops you need to provide the right temperature for optimal growth. The most common greenhouse crops require a temperature range of 64-75 ºF. This range is considered optimal for most plants grown in greenhouses around the world.

If the temperature inside your greenhouse is outside this range, photosynthesis will be reduced, inhibiting the growth of your crops, because they will not have the fuel to grow. Your crop quality will also be reduced outside the recommended temperature range, which is why growers never stray from it. 

Directly related to the temperature inside greenhouses is the humidity.

Ideal Humidity For Greenhouses

Greenhouses are so warm and humid, because, as the outside temperature increases, they can hold more moisture. Humidity plays a vital role as plants love water from the surrounding air. However, if the humidity levels become unbalanced, it can cause issues, such as encouraging pathogens and pests inside the greenhouse. 

The optimal relative humidity level for the majority of plants is around 80% (usually 65-75% during the night and around 80% in the day). If the humidity level increases or drops, your plant’s physiological processes are likely to slow down, causing slower growth and lower quality yield.

Even though the average is 80%, you should always correspond the humidity level with the type of plant or crop you are growing. However, high relative humidity levels are linked to diseases like botrytis or powdery mildew, which can quickly destroy cannabis, fruits, vegetables, or any other crop. Therefore, it is important to constantly monitor the humidity levels inside your greenhouse.

Ways To Control Temperature Inside Greenhouses

The biggest challenge to growing plants in a greenhouse is controlling consistency, transpiration, and condensation. Below are some ways you can easily control the temperature inside your greenhouse.

Location

The easiest solution is where you place your greenhouse. As the sun moves, you should select the right location when building your greenhouse. 

For example, in the summer, your greenhouse should be in the shade, but it should still be exposed to plenty of light during the day, and in the winter, you want your greenhouse to have as much sun as possible.

Automated Temperature Controls

Automated temperature controls that connect to a switch or vent opener can be installed to open or close windows or turn on a cooling or heating ventilation system when the temperature goes outside the temperature range. 

Natural Ventilation

Natural ventilation is important to prevent overheating, which can increase the humidity levels above the relative range. 

Most greenhouses have doors and windows that can be opened during the summer to reduce too much heat getting trapped inside, and let ample air flow through. In the winter, you can still open the windows slightly to allow ventilation, but be careful the temperature doesn’t drop too low. 

Ground-To-Air Heat Transfer Systems

A ground-to-air heat transfer system harnesses the temperature under the ground via pipes that allow air from the ground into the greenhouse.

These systems use a fan to push cooled air through the pipes and into the greenhouse during the day when it is hot, and during the night when it is cold, hot air (that has been stored in the ground) is pushed in. 

Fans & Heaters

Fans and heaters are generally used in large-scale operations such as farms, to extract air, or feed air into the greenhouse, which also reduces humidity. 

As air conditioners usually dry the air, humidity has to be closely monitored. 

When buying fans or heaters, check that they are the right size for your particular greenhouse, as you want to avoid overheating or over-cooling. 

Using Plants 

Adding plants to naturally shade the soil, keeps the soil moist and cool. Big leafy plants also help control humidity levels by shading the ground below, and they look great.

Misting & Fogging Systems

During hotter seasons, these systems remove heat by spraying a very fine mist into the air, removing the heat from the surrounding area via water evaporation. This is commonly seen in grow rooms

Misting and fogging systems also help control the humidity levels by temporarily raising the humidity around the plant.

Cooling With Water

To quickly cool down your greenhouse, you can spray some water on both the inside and outside. Be careful not to overwater your crops in the process, just a small amount sprayed towards the roof will be enough to cool the area. 

Using Water Tanks Or Buckets 

Like cooling with water, you can place black painted buckets to cool the temperature down. The black paint and the water will help absorb the trapped heat. 

Ways To Control Humidity Inside Greenhouses

As mentioned, temperature and humidity are directly linked, therefore, you also need to control humidity. 

Humidity can be controlled with some points listed above such as location, misting, cooling with water, using plants to shade, adding water buckets filled with water, and adding fans for air exchange. 

Alternatively, there are three other ways you can control the humidity inside your greenhouse:

  • Automated Humidity Controls
  • Proper Drainage (benches, pebbles, or rocks can be used)
  • Using Humidifiers 

How To Monitor Humidity & Temperature Inside A Greenhouse?

Many tools can help you monitor humidity and temperature levels inside your greenhouse. Although they are not essential to have, they are highly recommended to control consistency, transpiration, and condensation, particularly during your plant’s off-season, plus they will make your greenhouse-keeping much easier.

Temperature Sensors

Temperature sensors will give you the highest accuracy, stability, and reliability, which is why we recommend a platinum RTD (resistance temperature detector). Platinum RTD sensors offer a wide operating temperature range while maintaining high-temperature capabilities. 

Temperature Alarms

Installing an alarm will track potential problems inside your greenhouses, such as a power outage, temperature fluctuations, bug invasions, and water damage. With advances in technology, many alarms can be set up with your smartphone, alerting you when your temperature levels fall outside the optimal temperature range and switching on control systems. 

Temperature Control Systems

A control system can heat or cool your greenhouse when needed without you having to interfere, maintaining the temperature at an optimum level all year round for a successful yield. 

Remote Temperature Monitor

Monitoring the greenhouse temperature during the day is essential, as this is usually when the temperature fluctuates the most. An indoor air quality monitor displays temperature, humidity, and carbon dioxide (CO2) levels in real-time, letting you view it at any moment.

Humidity Sensors

A humidity sensor gives you very accurate readings for your greenhouse, detecting changes that alter the temperature or electrical currents in the air. Humidity sensors can also be connected to your air quality monitor, so you can monitor the humidity levels without having to open and close the greenhouse door. 

Summary

Growing produce in a greenhouse is very rewarding, but it doesn’t come without some challenges. One of the most difficult parts of maintaining a healthy greenhouse is controlling the ideal temperature and humidity. 

Most greenhouse crops require a temperature range of 64-75 ºF and an optimal relative humidity level of around 80%. 
If you have any questions about humidity or temperature, or what testing kits are best for your greenhouse, do not hesitate to contact our world-class team at Atlas Scientific.

Measuring Temperature & Humidity

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