Lesson-2 Function and Features of Greenhouse


Greenhouses are framed or inflated structures covered with transparent or translucent material large enough to grow crops under partial or fully controlled environmental conditions to get optimum growth and productivity.

  • The yield may be 10-12 times higher than that of outdoor cultivation depending upon the type of greenhouse, type of crop, environmental control facilities.

  • Reliability of crop increases under greenhouse cultivation.

  • Ideally suited for vegetables and flower crops.

  • Year round production of floricultural crops.

  • Off-season production of vegetable and fruit crops.

  • Disease-free and genetically superior transplants can be produced continuously.

  • Efficient utilization of chemicals, pesticides to control pest and diseases.

  • Water requirement of crops very limited and easy to control.

  • Maintenance of stock plants, cultivating grafted plant-lets and micro propagated plant-lets.

  • Hardening of tissue cultured plants

  • Production of quality produce free of blemishes.

  • Most useful in monitoring and controlling the instability of various ecological system.

  • Modern techniques of Hydroponic (Soil less culture), Aeroponics and Nutrient film techniques are possible only under greenhouse cultivation.


Although greenhouses look like simple structures, there's more to them than meets the eye. A reliable frame, covering, flooring and ventilation are all necessary for basic operation. To sustain the environment, a heating system and some automated processes, like irrigation via a dedicated water supply, may also be necessary.

2.2.1 The Frame:

A sturdy frame is necessary to maintain the plastic or glass panels that let in precious light and capture heat in the greenhouse. Larger greenhouses also need a foundation. The frame can be made of any number of materials, the most common of which are aluminum, wood, rigid PVC and galvanized steel. Aluminum lets in more light and can also support clip-on panels, making it the most common choice.

2.2.2 The Coverings:

Often referred to as glazing, the panels that cover greenhouses are specially designed to let in as much of the sun's radiation as possible. Ideally, they also provide insulation, are impervious to deterioration from ultraviolet radiation and are shatterproof. The panels can be made of heavy glass or any of a number of synthetic materials designed to maximize light exposure and help reduce heat loss. Glass lets in about 90 percent of the sun's radiation, helping to retain heat and hold up to ultraviolet light. Synthetics, while cheaper and sometimes stronger than glass, let in less of the sun's rays.

2.2.3 The Flooring:

Greenhouse floors need to have excellent drainage. Floors can be made of concrete, stone slabs, brick, sand or even dirt. Gravel floors provide excellent drainage and can be used in conjunction with a weed barrier to keep weeds from growing up through the rocks.

2.2.4 Greenhouse ventilation:

Ventilation is one of the most important components in a successful greenhouse. If there is no proper ventilation, greenhouses and their plants can become prone to problems. The main purpose of ventilation is to regulate the temperature to the optimal level, and to ensure movement of air and thus prevent build-up of plant pathogens (such as Botrytis cinerea) that prefer still air conditions. Ventilation also ensures a supply of fresh air for photosynthesis and plant respiration, and may enable important pollinators to access the greenhouse crop.Ventilation can be achieved via use of vents - often controlled automatically - and recirculation fans.

2.2.5 Greenhouse heating:

Heating is one of the most considerable factors in the operation of greenhouses across the globe, especially in colder climates. The main problem with heating a greenhouse as opposed to a building that has solid opaque walls is the amount of heat lost through the greenhouse covering. Since the coverings need to allow light to filter into the structure, they conversely cannot insulate very well. With traditional plastic greenhouse coverings having an R-Value of around 2, a great amount of money is therefore spent to continually replace the heat lost. Most greenhouses, when supplemental heat is needed use natural gas or electrical furnaces.

Passive heating methods exist which seek heat using low energy input. Solar energy can be captured from periods of relative abundance (day time/ summer), and released boost the temperature during cooler periods (night time/winter). Waste heat from livestock can also be used to heat greenhouses; e.g. placing a chicken coop inside a greenhouse recovers the heat generated by the chickens, which would otherwise be wasted.

Electronic controllers are often used to monitor the temperature and adjust the furnace operation to the conditions. This can be as simple as a basic thermostat, but can be more complicated in larger greenhouse operations.

2.2.6 Automated Watering System used in greenhouse:

Water is the most important element for plant growth. Without it, plant cannot survive. The manual system to watering is inefficient. When we water manually, the possibility to over watering is high. Some plant can drown when we supply too much water to them.

In order to overcome this problem, automatic greenhouse watering system is used. Sensors such as temperature sensor and soil moisture detector are used to control the watering system in a greenhouse

The system also has the capability to control the water level. In Drought prone area, a tank is used that acts as a reservoir tank in case of water problem. In this tank a sensor is used to ensure that water level is at its maximum level.


1. http://agritech.tnau.ac.in :  Low Cost Green Houses for Vegetable Production

2. http://home.howstuffworks.com : Greenhouse Features.

3. http://www.hgtv.com

4.  http://en.wikipedia.org/wiki/Greenhouse    

Last modified: Monday, 3 March 2014, 10:06 AM