Maintaining Optimum Climate Control in the Greenhouse for Plant Success - Gothic Arch

Greenhouses
The warming weather is a reminder to

greenhouse owners to examine

climate control strategies inside the structure so as to ensure crops grow strong and

healthy throughout the warmer days and nights ahead. Without such consistency, plant

damage and even death can occur.
The experts at Gothic Arch Greenhouses, a family owned and operated greenhouse and

supply business for nearly 70 years, can partner particular circumstance with quality,

affordable, easy to use equipment needed to help ensure optimum climate control inside the

greenhouse.
“It boils down to three things,” says William H. “Buzz Sierke, third generation

president of the Gulf Coast based business, “correct lighting, temperature and humidity.

To know those, you first must know what conditions are needed for the particular plants

being grown in the greenhouse.” Sierke encourages all growers, commercial or hobbyist, to

think about where a particular plant originates. Take ornamentals and tropicals for

example.
Ornamentals can tolerate nighttime temps as low as the mid-50’s while that

temperature can damage tender tropicals that don’t want it below 60 degrees. On the other

hand, temperature needs for successful seed germination varies as do those of cool or warm

weather vegetables. “It all depends on what you’re trying to grow, and under what

circumstances,” Sierke says.
Rising temps means higher humidity which, for some crops like Tropicals, is good, for

others like some ornamentals, it could be deadly. If the circumstance calls for decreasing

humidity levels inside the greenhouse, venting or exhausting the humid air is in order.

That means air movement. A closed greenhouse needs a fan to blow hot stale air out of the

structure and bring fresh cooler air inside via intake shutters mounted on the opposite

end of the structure to create consistent environmental control.
Gothic Arch Greenhouses offers a huge selection of greenhouse ventilation fans like

our favorite, the Air Flow HAF fan, a specialized greenhouse fan that allows adjustable

air patterns to create a uniform temperature throughout the structure to suit any growing

need. According to Sierke, the Air Flow HAF is by far, the most versatile, energy

efficient, best valued HAF fan available.
For larger greenhouses, Sierke says the same optimum growing conditions can be

maintained by using greenhouse cooling system which utilizes the hot

air inside the greenhouse to evaporate the moisture from plant surfaces thus cooling the

inside temps by up to 20 degrees.
Whatever environmental control system you choose, you’ll need control.

Arch Greenhouse

can help you choose from a wide selection of the most reliable automatic one, two,

or manual variable speed thermostat controls available on the market today, designed

especially for greenhouses.
And no environmental control plan would be complete without a timer to give freedom

over how much or how little light plants get and when. The right automatic timer allows

control over automated watering and mist systems, fans, heaters, and other equipment too,

allowing one time for other activities.
So, as the days grow longer and warmer, take the time now to plan how to create and

maintain consistent optimum growing conditions needed for successful healthy plant growth

inside the greenhouse during the days ahead. Gothic Arch Greenhouses is the most trusted

name in greenhouses with over 70 years of dependable service providing made in the USA,

do-it-yourself greenhouse kits, related accessories, and the right environmental control

systems to fit any need.
Most of the greenhouses in the Netherlands are so-called Venlo greenhouses. This

construction is strong, allows a lot of light to pass through, is relatively inexpensive.

The Venlo

greenhouse is ideal for the Dutch climate conditions. But which design fits in

another climate, such as a desert or a humid climate? The Greenhouse Horticulture & Flower

Bulbs Business Unit of Wageningen University & Research developed a method for designing

one based on local conditions: Adaptive Greenhouse Design. An interactive tool

demonstrates the operation and benefits of this method.
The Freshteq Fieldlab offers companies and organizations a breeding ground for the

development of innovative applications for international horticulture. Within the Freshteq

Fieldlab – based in the World Horti Center in Naaldwijk – there are various activities

and initiatives. ERDF Freshteq is made possible in part by the European Regional

Development Fund (ERDF).
A tool to predict how a crop will grow under certain conditions
An example of the Freshteq initiatives is the Adaptive Greenhouse Design tool, an online

tool developed by WUR. With the tool, an optimal greenhouse design can be made for a

specific region.
Today, more than two-thirds of new greenhouse construction is covered with film

plastic. Besides the obvious advantages of low-cost, low taxes, ease of covering, four

year life and additives such as anti-drip and light diffusion, there are other properties

that should be considered when purchasing the material.
Manufactures have worked hard to

provide a material that will give good service, high light transmission and properties

that improve plant production. Most greenhouse polyethylene film is manufactured as a

coextrusion of three or more layers with different polymers and additives. Each of these

layers contributes to the quality of the film by adding tear and puncture resistance, high

light transmission, IR retention, UV blocking, dust control and color pigments.
The following reviews some of these often overlooked properties that could influence

your purchase decision.
Thermicity
A plastic film is considered an infrared film (IR) if less than 25% of the heat

generated within the greenhouse is allowed to escape. The lower the percentage, the lower

the winter heating bill. Regular greenhouse grade polyethylene film allows 30% to 60% of

the IR heat to escape.
Plastic manufacturers have found that mineral based additives, such as ethyl vinyl

acetate (EVA), calcined kaolin clay or synthetic aluminum silicate can reduce the

radiation loss. This material is usually added as one of the inner layers in the

copolymer.
These additives may reduce light transmittance slightly but they also diffuse the

light spreading it evenly inside the greenhouse reducing shadows and allowing more light

to reach lower into the canopy. It also helps to average out leaf temperatures at the top

of the plant canopy reducing the amount of shading needed.
Flammability
Often building officials question a grower applying for a building permit as to the

flammability of the film plastic. Section 3102.3 of the International Building Code states

that “Plastic less than 20 mil thickness or located less than 30 feet above the floor as

used in greenhouses where occupancy by the general public is not authorized is not

required to meet the fire propagation performance criteria of NFPA 701 (National Fire

Protection Association)”.
Low density polyethylene plastic is an oil-based product with a high heat value of

about 20,000 Btu/pound. It will burn if in contact with an external flame but does not

maintain a flame by itself for very long. The additives used in copolymers could affect

this some so obtaining the test results from the manufacturer may be necessary. Also

copolymer film may not get building official approval for retail greenhouses.
Photoselective films
This

greenhouse film absorbs or reflects specific wavelengths of light. They can enhance

plant growth, suppress insects and diseases and affect flower development. Red films such

as Dupont IR and Smartlite Red film reduce PAR light and create a shading effect. They

have also been shown to improve rose yield and quality.
Disease Control
Plastic film manufacturers have developed disease control films that absorb UV

radiation in the 340 to 390 nm wavelengths. These have been found to reduce the population

of insects such as whiteflies, thrips miners and aphids. The material can also control the

spread of certain diseases such as botrytis.
As bees need UV to navigate, if you are using bees to pollinate plants in the

greenhouse, purchasing a film that allows some of the UV part of the light energy spectrum

to pass through may be important.
Off-gassing from film
Recent research by Dr Sarah-Jeanne Royer at the University of Hawaii in Manoa has

found that LDPE film produces methane and ethylene gas when exposed to sunlight. In large

poly covered ranges the amount of gas produced may be significant. As these gases can

affect plant growth, additional research is needed to determine the level that may have an

effect.