A greenhouse’s most important function is to provide the perfect environment for plant growth. Storing the sun’s energy and harnessing it to benefit your crop is the key to all good greenhouse design. Ventilation is essential for balancing an indoor climate that makes the most of the powerful solar spectrum, while keeping an optimal temperature and air quality to help your plants thrive!
Air exchange is important not only for providing the carbon dioxide and fresh air that plants need for photosynthesis. It also helps keep the temperatures inside your greenhouse regulated. In Winter, a greenhouse’s function is to store heat from the sun, creating a warmer temperature in the greenhouse versus outside of it. But in the Summer, an unventilated greenhouse can turn into a furnace, holding withering heat instead of protecting your plants from the elements.
Cooling a greenhouse on a hot day is a difficult task without a good ventilation layout. The most effective greenhouse ventilation system is will use exhaust fans, setup to blow hot, stale air out, and intake shutters mounted opposite, to bring fresh, cooler air in. (Shown in picture)
An exhaust fan system should be able to make a complete change of air in 1 to 3 minutes in summer to keep temperatures in the greenhouse at a reasonable level. One minute or less is best for small greenhouses; Two to three minutes is acceptable for large commercial-sized greenhouses.
Plants require fresh air year-round, which is why it is important to have equipment with options like louvered fans, motorized shutters, and variable speed motors that will help prevent heat loss when it is cold outside.
Roof and side vents are also helpful to supply fresh air to plants and cool your greenhouse. This is also ideal for venting during cold months, because if used with automatic vent openers, fresh air can be supplied to plants gradually, reducing any “temperature shock”. HAF circulation fans are highly recommended for use with side and/or roof mounted vent systems. These fans move air throughout the greenhouse, eliminating hot and cold spots. The increased air movement helps to expel hot air out of the window vents and provides fresh air for plants.
Air movement, cooling, and some additional humidity can be provided by an evaporative cooler. It will provide additional active ventilation, bringing in cooler air and exhausting the hotter air through existing roof vents. Evaporative coolers can be used in conjunction with exhaust shutters like in the diagram below.
A combination of shade, proper ventilation, and an evaporative cooling system, misting system, fogger, or wet wall can be very effecting for regulating high temperatures. A greenhouse allows you considerable control over your growing environment; however, even using all of the items mentioned above, you can expect a greenhouse to still not be much cooler than the outside temperature in extremely hot, humid areas.
Many plants thrive in warm, humid environments, but this is not the optimal climate for all plants. Researching your particular crops’ needs can help you to find the right combination to keep your plants healthy and happy. The effectiveness of your ventilation, your cooling, your humidity, and your outdoor ambient temperature are all very important factors to keep in mind when choosing your greenhouse crops for mid-summer. For expert advise to guide your greenhouse ventilation plan, give the experts at Gothic Arch Greenhouses a call today. We’ve got the knowledge and experience to help you make the most of your growing space, all year round.