Structures & Equipment
Putting on your summer shades
By Duane Van Alstine
A properly installed curtain system could help maintain an ideal climate inside your greenhouse.
By Duane Van Alstine
As energy and production costs continue to rise for the horticulture sector, commercial greenhouse growers need to do all they can to operate more efficiently. One way growers are doing this is by installing energy curtain systems in their greenhouses.
Many growers have already seen, or heard of, the benefits that energy curtains can provide during the winter when heating costs are high. However, growers are also beginning to realize the benefits that curtains can provide during the summer, acting as shade to their crops when the days are longer and sunlight levels are significantly higher. It doesn’t take long for the radiant heat from the summer sun to send the temperature inside the greenhouse soaring far beyond what’s desired, but a properly installed curtain system can help to maintain an ideal climate inside.
Energy curtains, also referred to as energy screens, are retractable components made from composite materials. Curtains are installed above or below the trusses, but most often above to accommodate supplemental lighting. They can be installed to open and close across the greenhouse, from gutter to gutter, or can cover and retract across the length of the greenhouse. A flat curtain system is typically the most cost-efficient choice, but how your curtains are installed depends on the needs of your crops.
The three most common categories of curtain materials are nonporous, porous, and semi-porous. Nonporous materials, such as poly film, are generally not ideal for greenhouse curtains as they don’t allow for condensation from the roof to penetrate. A semi-porous material is generally the most practical choice for both heat retention and shading. Typically made from alternating pieces of aluminized and clear polyester or acrylic fabric woven tightly together, semi-porous curtains allow condensation to pass through with little air exchange between the upper and lower sides of the curtains when they are closed.
Use in the summer
When installed and used correctly, your energy curtains will help to create and maintain an ideal growing environment for your plants. Curtains should be closed when they can improve conditions inside the greenhouse, but they can be opened when outside conditions are more favourable.
In the winter, curtains can help keep heat inside the greenhouse. For example, when the sun goes down in the winter, your curtains will likely need to be closed completely to ensure the heat doesn’t escape. But in the summer, curtains are also used to keep the heat out of the greenhouse. When daytime temperatures rise, curtains can help reduce indoor temperatures and provide shade for your crops. Orchids, for example, are an extremely sensitive plant that can burn quickly if too much sunlight is allowed in their growing area. Having shade curtains can help to reduce and disperse sunlight so plants are protected. On summer nights, slightly or completely open curtains will allow the cooler air to hit your crops.
Your curtains can also be used in conjunction with your roof vents to help manage the humidity in the greenhouse. Having your vents open while the curtains are closed, or nearly closed, will allow fresh, cooler air inside the greenhouse while still having a barrier that prevents too much colder air from hitting the crop. If the humidity is too high inside the greenhouse, the curtains can be opened slightly along with the vents to lower the humidity inside. Your curtains can also be used in conjunction with your heating system to reduce humidity. You may find that humidity buildup can be problematic on summer mornings, but turning up your under-bench heat while opening shading and vents will get rid of the humidity quickly. Once the humidity is manageable, the shading and venting can be returned to automatic settings. Using your shade curtains in conjunction with your roof vents and your heating system will help ensure your crops are benefiting from an ideal environment while saving on energy costs.
Curtains also have the potential to decrease your water use during the summer. When your curtain system is working in conjunction with your irrigation system, it will reduce your crops’ needs for water uptake. Strict water regulations and drought control takes effect in many areas during the summer months, so growers should do all they can to obtain maximum value from their water resources. Be sure to talk to an expert to see how a shade curtain system can reduce your irrigation costs.
Automate energy curtains for maximum efficiency
Your crops will see the most benefit from your curtains during the spring and summer months if they’re controlled by a central environmental computer. Automating your shade curtains is important, not only because they control the amount of natural sunlight that’s allowed into the greenhouse, but because they affect other environmental conditions including lighting, temperature, airflow and humidity. All of these factors can be a lot to keep track of if you’re only using a manual or semi-automatic system. Full automation will provide peace of mind that your curtains are providing your plants with their ideal environment. We recommend that you review your controls over as many past seasons as possible, using this information to help improve them for the current season. An automated system will make things easier but it’s equally important that you avoid becoming complacent with the parameters you have set. A day in June can be drastically different from a day in July, so it’s important that you’re paying constant attention to your controls and making the necessary changes to avoid negative effects on your crops and minimize energy wasted.
The type of curtain system and material you have installed in your greenhouse will depend on various factors including the regional climate, the style of greenhouse and the crop environment. There are numerous options available, so work with knowledgeable experts who will ensure you’re getting the best curtains at the best value for your plants.
Duane Van Alstine has been in the horticulture industry for 20 years, previously having been the operations manager of a 380,000 square foot facility. In 2011, he left the greenhouse to take on Special Projects for GGS Structures Inc. For more on energy curtains, visit ggsstructures.com