Chapter 19Chapter 19

Greenhouse and Greenhouse and Other StructuresOther Structures

Three main purposes of Three main purposes of greenhouse structure:greenhouse structure:

To provide a controlled growing To provide a controlled growing environment for plants whose environment for plants whose economic value justifies the expense.economic value justifies the expense.

To permit the growth of plants in To permit the growth of plants in regions where survival outdoors is not regions where survival outdoors is not possible.possible.

To extend the season of growth for To extend the season of growth for plants at times when they would plants at times when they would normally go dormant.normally go dormant.

Detached A-frame TrussDetached A-frame Truss

Is the most expensive to build and Is the most expensive to build and heat, but provides the best heat, but provides the best environment control.environment control.

Quonset-style Greenhouse Quonset-style Greenhouse (hoop house)(hoop house)

Requires new covering nearly every Requires new covering nearly every year.year.

Traditionally people mostly Traditionally people mostly used plastic to cover used plastic to cover greenhouses since it was greenhouses since it was cheaper than glass, but cheaper than glass, but because of the recent rise because of the recent rise in cost of all petroleum-in cost of all petroleum-based products, plastic and based products, plastic and fiberglass now rival glass in fiberglass now rival glass in initial cost.initial cost.

Eight common types of Eight common types of greenhouse Materialsgreenhouse Materials

Glass Fiberglass Glass Fiberglass

Soft-plastic* Shade fabricSoft-plastic* Shade fabric

* Three different types of soft plastic: polyethylene, * Three different types of soft plastic: polyethylene, vinyl, polyvinyl fluoride.vinyl, polyvinyl fluoride.

Polycarbonate rigid panelsPolycarbonate rigid panels

Acrylic rigid panelsAcrylic rigid panels

Hotbed: Hotbed: a low growing structure that uses a low growing structure that uses electric cables or heating pipes to electric cables or heating pipes to provide the warmth needed to provide the warmth needed to propagate, start, or harden off propagate, start, or harden off plants.plants.

Cold Frame-Cold Frame- a low growing structure a low growing structure that uses the heat of sunlight passing that uses the heat of sunlight passing through glass or plastic to provide through glass or plastic to provide the warmth needed to propagate, the warmth needed to propagate, start, or harden off plants.start, or harden off plants.

Why is the need for supplemental Why is the need for supplemental heating apparent in a greenhouse?heating apparent in a greenhouse?– A greenhouse lacks the ability to retain A greenhouse lacks the ability to retain

sufficient heat after the sun sets.sufficient heat after the sun sets.

Nearly all greenhouse systems are Nearly all greenhouse systems are automated now, and many involve automated now, and many involve both primary and back-up both primary and back-up (emergency) systems.(emergency) systems.

The even distribution of air The even distribution of air throughout the greenhouse is throughout the greenhouse is essential for consistent temperatures essential for consistent temperatures and uniform plant growth.and uniform plant growth.

Greenhouse air should move slightly Greenhouse air should move slightly as often to minimize mildew and other as often to minimize mildew and other diseases of plants that proliferate diseases of plants that proliferate under stagnant conditionsunder stagnant conditions

Ventilation SystemVentilation System Roof & Side* Exhaust FansRoof & Side* Exhaust Fans

Retractable Roof Fan & convection Retractable Roof Fan & convection tube tube

* oldest method of ventilation

Three basic approaches taken with Three basic approaches taken with a greenhouse depending on time a greenhouse depending on time of year, and geographic location:of year, and geographic location:

Shading the glass to reduce light Shading the glass to reduce light intensity.intensity.

Ventilating to allow cooler outside air Ventilating to allow cooler outside air to replace warm air inside.to replace warm air inside.

Promoting heat exchange through Promoting heat exchange through water evaporation.water evaporation.

Two ways of providing shade Two ways of providing shade in a greenhouse:in a greenhouse:

ExternallyExternally- spraying on a - spraying on a compoundcompound

InternallyInternally- Fabric or cloth - Fabric or cloth suspended above crop to reduce suspended above crop to reduce light intensity.light intensity.

Greenhouse ventilation systems Greenhouse ventilation systems bring fresh air into the greenhouse to bring fresh air into the greenhouse to replace the warm internal air.replace the warm internal air.

Especially during hot weather, Especially during hot weather, ventilation alone is not enough to ventilation alone is not enough to cool a greenhouse.cool a greenhouse.

Both fan and pad cooling and fog Both fan and pad cooling and fog evaporative cooling systems can evaporative cooling systems can reduce greenhouse temperatures reduce greenhouse temperatures from 10 degrees to 30 degrees F from 10 degrees to 30 degrees F below the outside air.below the outside air.

Cooling:Cooling:

Fan and pad Fan and pad - Uses exhaust fans and - Uses exhaust fans and continuously wet pads of excelsior (a continuously wet pads of excelsior (a fibrous porous material) cross fluted fibrous porous material) cross fluted cellulose, aluminum fibers, or glass fibers. cellulose, aluminum fibers, or glass fibers. Cools through a re-circulating water system.Cools through a re-circulating water system.

Fog evaporativeFog evaporative- Uses a high pressure - Uses a high pressure pump to create a fine mist. As the fog pump to create a fine mist. As the fog disperses through the greenhouse, the disperses through the greenhouse, the evaporation causes desired cooling without evaporation causes desired cooling without wetting plants.wetting plants.

Greenhouse and Energy Greenhouse and Energy ConservationConservation

Greenhouse management has shown Greenhouse management has shown an orientation of crop types to an orientation of crop types to geographic regions. Crops needing geographic regions. Crops needing higher temperatures are being grown higher temperatures are being grown more in southern states than in more in southern states than in northern ones and vice versa. They northern ones and vice versa. They are also constantly trying new are also constantly trying new conservation techniques.conservation techniques.

The principle disadvantage of adding The principle disadvantage of adding an extra layer of plastic to an an extra layer of plastic to an existing greenhouse is the reduction existing greenhouse is the reduction of light intensity.of light intensity.

True or False: Large amounts of heat True or False: Large amounts of heat are lost through the concrete or are lost through the concrete or wooden sides of the greenhouse?wooden sides of the greenhouse?

After DarkAfter Dark::– When most heat is lost in greenhouseWhen most heat is lost in greenhouse– When fuel consumption is greatestWhen fuel consumption is greatest

True

Automated blanket systems have Automated blanket systems have been developed for greenhouses been developed for greenhouses because they can be set on timers.because they can be set on timers.

The focus of conserving energy has The focus of conserving energy has caused the greenhouse industry to caused the greenhouse industry to enter into a period of change.enter into a period of change.

The style of benches, materials used, The style of benches, materials used, and arrangements within the and arrangements within the greenhouse depend upon the crop greenhouse depend upon the crop being grown.being grown.

Three functions a greenhouse Three functions a greenhouse must fulfillmust fulfill

Must drain quicklyMust drain quickly

Must be of a width that allows Must be of a width that allows workers to reach into their centerworkers to reach into their center

Must maximize the crops Must maximize the crops exposure to lightexposure to light

Tomatoes and lettuce require ground Tomatoes and lettuce require ground beds.beds.

Raised benches are used in the Raised benches are used in the production of pot crops as well as cut production of pot crops as well as cut flowers.flowers.

Raising the bed above the ground Raising the bed above the ground allows air to flow more freely around allows air to flow more freely around the crop and permits a warmer root-the crop and permits a warmer root-zone temperature to be maintained.zone temperature to be maintained.

A framework of pipe constructed A framework of pipe constructed above a regular bench allows for above a regular bench allows for hanging baskets to be grown above hanging baskets to be grown above another crop.another crop.

The most important quality of a bench The most important quality of a bench is its capacity for rapid drainage.is its capacity for rapid drainage.

Any wood used in the construction of Any wood used in the construction of greenhouse benches should be greenhouse benches should be preserved with some type of preserved with some type of preservative.preservative.

One determines the number and width One determines the number and width of aisles within a greenhouse by of aisles within a greenhouse by finding the width of the carts needed finding the width of the carts needed in the aisles, and whether the crop can in the aisles, and whether the crop can be worked from one side or needs to be worked from one side or needs to be accessible from both.be accessible from both.

Typical cross-bench Typical cross-bench arrangementarrangement

Different types of bench Different types of bench arrangements:arrangements:

Cross-bench arrangementCross-bench arrangement-aisles along the -aisles along the sides and between the benches, is least sides and between the benches, is least efficient use of space for growing.efficient use of space for growing.

Peninsular benchingPeninsular benching- features a wide - features a wide central aisle to accommodate carts and central aisle to accommodate carts and other equipment. The narrow aisles other equipment. The narrow aisles between benches allow access by workers between benches allow access by workers and efficient space for growing.and efficient space for growing.

Length-of-houseLength-of-house- utilizes growing space - utilizes growing space efficiently, but workers must walk the efficiently, but workers must walk the length of the house to get to the other side length of the house to get to the other side of the bench.of the bench.