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After making decisions of geographical location, proximity of market, fuel supply and investment in land for setting up green house, following points should also consider about the location of green house:
(i) It should be sunny and sunlight should not be obstructed at any time during the day.
(ii) Soil should be well drained and area should be free from flooding.
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(iii) It should not be exposed to cold, bleak, winds otherwise fuel bill may escalate for this a wind break will.be very effective in protecting from winds.
(iv) The land should be well leveled or gently sloping toward south or south east side.
(v) There should be regular water supply.
(vi) There should be sufficient land for future expansion.
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Other considerations:
1. Arrangement of houses:
It depends upon the number of houses, size of range, and purpose for which it is to be used, the arrangement should be such that it saves the movement of workers and all the houses get sunlight whole of the day without interruption. For this direction of the houses to be constructed, pitch of the houses and distances between two houses are important factors.
2. Direction:
The single houses are constructed in N-S-direction enjoying the sunlight whole of the day on both sides equally. However, during afternoon when sun light strikes obliquely, much heat and light is reflected back in the atmosphere. Frame works will also caste lot of shade, on the contrary, when houses run east and west side, the sunlight enters in the green house from the sides. In the morning and afternoon, it strikes roof obliquely. During the middle of the day, light strikes at right angle so green-house get maximum light and heat, however, southern part of green house will be comparatively more warmer then north side.
Normally attached houses run north and south so all the houses get full advantage of light and heat whereas single houses run east west side.
3. Connected houses:
Many single even span style houses are joined together so they make ridge and furrow house. In such type houses there are no side walls between individual units. The number of houses is based on requirement of crop or crops to be grown.
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According to the construction, connected houses are as follows:
i. Saw-tooth houses:
As the term indicates, these types of houses consist of a series of lean to green-houses connected together. The elevated portion of saw tooth opening is directed away from prevailing winds to aid its ventilation generally, these are covered with plastic sheet.
ii. Multi chamber:
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These types are modification of Quonset type detached green house and called as barrel vent green-house consists of Quonset type structure set on side wall. The height of side wall is about 2.10 to 3.0 m high.
iii. Shade net houses:
In tropical climatic countries where sunlight is very bright and to reduce it shading nets of different colour and density used according to the need.
Normally green coloured shade nets are very popular followed by black or white. Saran cloth made up of white plastic is also used. These are not true green-houses but are very useful where frost is not a problem. Green foliage crops are commonly green.
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iv. Lath house:
These are generally made up of wood or wood with a metal frame work. The degree of shade is determined by the distance between two laths which is generally kept about 5 cm. The width of individual lath is 5-7.5 cm and length is about 3.0 to 3.50 m. In such structures green foliage crops, ground covers or other crops are grown which require partial shade or broken sun light.
The advantages of detached type are disadvantages of attached type and vice versa.
4. Low tunnels:
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These tunnels are 1-1.6 m in height covered with clear polyethylene. Some-time very low height tunnels of 30-60 cm in height only are made keeping the height of crop and duration into consideration. These have several advantages over poly-houses and green houses and have been found very useful being simple and of low cost in nature.
These are mostly used when adverse weather conditions are limited to short duration. Such conditions are found in north-west plains from 15th Dec. to 15th March or during May to August. During winter month’s polyethylene of 100 mil is used whereas during summer months, black, white or green netlon is used to cut the sunlight and to provide partial sun light.
The selection of covering material depends upon months and duration. Structure is made of steel rods of 4 mm thickness which can be easily bended to give a desired shape. These are fixed in the ground at distance of 1-2 m, after use, the structure and covering material is stored for the next time.
