CLIMATE CONTROL SYSTEMS

With your greenhouse sealed and ready to endure the elements, you now can focus on making the climate inside your greenhouse ideal for the plants you want to grow. While the main idea of the greenhouse is to capture the light and warmth from the sun, you can’t rely on sunlight alone if you plan to grow year round. That’s why the use of environmental controls is important. When you use them, you give your plants an environment that doesn’t exist where you live.

THE FIVE FACTORS OF ENVIRONMENTAL CONTROL

You learned about what the plants need at the beginning of this article, but now is the time to revisit and expand on those needs. These five factors will change the way your plants grow dramatically, and putting control of them in your hands will give you so many growing advantages.

1. Temperature

The ideal temperature for growth is going to vary from plant to plant. Some like it hot, and others will prefer cooler temperatures. So before bringing plants into your greenhouse, it is important to know their preferences. While you might not give each one the perfect temperature, you will find a great range for multiple plants to thrive.

This is when maintaining control of those temperatures becomes vital. As plants grow, they will start giving off their own heat, and when you mix that with the temperature being provided by the sun, it can turn a warm climate into something more akin to a tropical one. Your plants at the lower end of your temperature range are going to suffer at this point.

2. Humidity

Plants will not only produce heat but they give off moisture as well. Like temperature, there will be plants that love the excess humidity, but others will start becoming prone to molds and diseases, which can then spread to your other crops.

While you can maintain control over the humidity levels in the greenhouse, it is going to be a delicate balance between avoiding molds and diseases while not drying out your plants.

3. Sunlight

Some plants thrive with intense sunlight but others will prefer less intensity.

When you control this factor, you give all of your plants their preferred lighting arrangements. You can use shade cloths, curtains, and UV filtering covers during the summer months. During the winter, you can control this with grow lights to mimic the sunlight that just isn’t there at this time of year.

4. Ventilation

This one factor plays the most critical role as it can affect all the other factors except sunlight. It can cool things down, regulate humidity, and provide airflow, which gives your plants the carbon dioxide they need.

Therefore, it’s important to have something in place in your greenhouse where you can let fresh air come in and move around the greenhouse.

5. CO₂ enrichment

You might not get too invested in CO₂ enrichment when you’re starting out, but as time goes on, start monitoring the carbon dioxide that is in your greenhouse.

You see that too much or too little CO₂ isn’t good for your plants. By monitoring this, you will control it. If levels are dropping, you can open your vents to get some fresh air and CO₂ into your greenhouse. And if it rises, you can close up your greenhouse.

By giving your plants the right amount of CO₂, you will see crops mature faster, and you will harvest more throughout the year.

While that covers the basics of controlling this created climate, you probably want to know what other solutions are available for heating, ventilation, humidity, and even CO₂ enrichment.

HEATING

You may have assumed that there is a “perfect” temperature for your greenhouse. While there are plants that will appreciate it a little cooler, you didn’t buy a greenhouse to keep it cool. That means there is an ideal temperature, and that is roughly between 80 and 85 °F. So it’s going to be plenty warm in your greenhouse.

This temperature is pretty easy to reach once the growing season is in full swing, but once the days get shorter and the temperatures fall, you’re going to need to get your greenhouse warm again. But what’s available to you?

• Thermal mass: This is a large object that will absorb and hold heat. Many greenhouse hobbyists will use large barrels filled with water as a thermal mass.

• Insulation: Just like you learned in the weatherproofing section, insulating your greenhouse is a fairly inexpensive way to hold on to heat. This also means that when those colder months set in, you can insulate the entire north-facing wall to catch more heat. .Compost: It can give your plants a lot of nutrients but can also generate heat, especially if it is composed of manure.

• Electric heaters: This is when things will factor in with costs. However, a lot of electric heaters will have their own thermostat, so you don’t have to worry about them running all day. Please note that you don’t want to use a regular household heater. There are greenhouse heaters that are built for the task, or you can use a heater made for outdoor use. You should just ensure that the heater is built to meet the requirements of your greenhouse.

• Gas heaters: If your greenhouse is freestanding, it means you probably don’t have access to the natural gas supply that goes to your home. There are propane heaters, and all you need is a tank like what you’d use for your outdoor grill. Just remember that you will have to make sure that there is some ventilation to let the fire burn properly and keep harmful gases out of your greenhouse. .Kerosene heaters: These operate the same way as gas heaters, and they need ventilation, too.

While they aren’t the best idea because they are impractical in terms of the labor you’d do, you can use a wood stove or a rocket mass heater.

Again, they work great, but they require a lot more effort than they’re worth, especially when you have the other options.

VENTILATION

It’s been mentioned a few times throughout the book the importance of ventilation and the reason, but how can you get that crucial airflow to your plants?

• Vents: Vents alone would be “passive ventilation,” where openings (vents) bring air in naturally.

The most popular vents for greenhouses are roof vents and side-wall vents. Heat rises, while cooler air settles near your foundation. This makes roof vents the most effective, albeit more expensive. This can also be done with windows or even a screen door attached to the greenhouse.

With a low profile greenhouse, you would need to have forced cooling to get the same effect that taller structures have.

• Fans: If vents are passive, then fans would be “active ventilations” because they require an outside force to create the same effect.

Fans are the major tool for getting that active ventilation, and they can circulate air within the greenhouse. While this is a great idea anyway, get serious about fans if your building is in a place with poor ventilation.

Knowing what fan to get and where to place it is the tricky part. If fans are placed higher, then you get better circulation. But your greenhouse may be too large or the design may not be ideal, so you should always check the fans’ capacity. You may have to get a couple or more to provide the much-needed airflow.

COOLING

Keep in mind that ventilation is going to be a major step in cooling your greenhouse. Some greenhouses can be retrofitted with a blind system that can shade your plants when the sunlight is too intense. You can also use shade cloth or shade paint. The problem with the latter is that while it is easy to clean off, it can be a long process when you just need to shade your plants for a few hours in the day.

CO₂ ENRICHMENT

CO2 levels will change by time of day and season, but in a well-ventilated greenhouse, you usually get all the CO2 your plants need. However, your greenhouse might not be in an area where you get that ventilation. This is where your fans should be able to do the work for you.

You can do CO2 supplementation by bringing carbon dioxide tanks into your greenhouse and giving your plants the amount they need to thrive. While supplementation sounds like a great idea because CO2 will provide additional heat in the winter and you will get more bountiful crops, it is better to rely on the natural air.

CO2 can come with a higher production cost, and you will have to modify your greenhouse even further in order to use supplementation. Even with extra CO2, not every plant is going to respond well, and it’s really only beneficial to younger plants. You also can’t forget that higher levels of CO2 can be toxic to plants and humans, so it’s better to leave supplementation to commercial greenhouse gardening.

HUMIDITY

Giving your plants the right heat can give them a push, but when they have humidity as well, then they will really thrive. Much like your heating requirements, every plant is going to have its own needs, but your optimal level is going to be 80%. This is when your plants will reach their highest growth rates and give you the best yields. Of course, tropical plants will need significantly more humidity, while plants like succulents and cacti will prefer dryer conditions, so keep that in mind when bringing plants in.

Getting your greenhouse humid enough will come from your watering routines and maintaining the proper temperatures in your greenhouse. There will be times that you will have a struggle with trying to vent your greenhouse without drying out your plants but providing moisture is still relatively easy. The real challenge will come with trying to prevent excess humidity. Higher humidity levels will put your plants at risk for diseases and fungal infections.

Controlling Your Humidity

You are going to be looking for ways to get your humidity levels down. Luckily, there are a lot of ways that you can do this that just require some monitoring and good greenhouse practices, as mentioned below.

• Avoid leaving moisture on plants: Certain plants don’t like top watering methods, and this will spike your humidity levels, too. Try using drip irrigation or watering at the base of the plant instead.

• Water during the day: At night, moisture is just going to linger in the air as temperatures drop.

• Keep excess water out: Sometimes water will just get everywhere, and that’s why it’s important to have a floor that will provide drainage. You also want to eliminate any pools of water in any container that isn’t being used for plants. They not only provide excess moisture, but also they’re ideal breeding grounds for pathogens and pests.

• Make sure you ventilate: This is one of the most critical factors for a successful greenhouse.

• Turn the heat up: Higher temperatures will promote evaporation, so in the winter, make sure you are using alternative heat. Just don’t forget to turn it down at night to prevent condensation.

• Use desiccants: These use a chemical process that pulls excess moisture in. While these can help, it will become expensive in larger greenhouses.

• Buy a dehumidifier: There are two types of dehumidifiers-chemical and mechanical. Mechanical dehumidifiers will use the same techniques as refrigerators or heat pump systems, and chemical dehumidifiers will work more like desiccants.

This is a wise investment if you are plagued with high humidity levels, and they will also have humidistats that allow you to keep the right amount of moisture in the greenhouse.