The document discusses planning and design considerations for greenhouses. It covers selecting a site, orientation, interior layout, structural design loads, foundations, frames, cladding materials, roof slope, and how interior components can influence the greenhouse environment. The key factors to consider for greenhouse design are the local climate conditions, structural support needs, optimizing light transmission, and minimizing shading from interior equipment.
1. BIRSA AGRICULTURAL UNIVERSITY
Protected Cultivation and Secondary
Agriculture
LECTURE 7: PLANNING AND DESIGN OF GREENHOUSE
BY
DR. PRAMOD RAI
DEPARTMENT OF AGRICULTURAL ENGINEERING
2. The GH design must deal with the local outdoor
conditions, like :
Minimum, maximum & average temperature,
Humidity,
Solar radiation,
Clearness of the sky (clouds),
Precipitation (rain, hail and snow),
Average wind speed & wind direction.
Greenhouse Design
6. GH design based on cost of construction or
technology
Low cost or low tech GH
Medium cost or medium tech GH
High cost or hi-tech GH
7. Planning and Design of Greenhouse
1. Site Selection and Layout
2. Design Load
3. Construction
4. Safety
5. Utilities
8. 1. Site Selection and Layout
Recommendations for layout, design and
construction of GH structures (IS 14462:1997)
9. While selecting the site for construction of a GH, following points
should be considered for the optimum growth & development of
plant:
The site should be free from shadow.
The site should be at a higher level than the surrounding land with
adequate drainage facility.
Availability of good quality irrigation water and electricity to run the
fan & pad cooling system.
pH of the irrigation water should be in the range of 5.5 to 7.0 and EC
between 0.1 to 0.3 mS/cm.
pH of the soil should be in the range of 5.5 to 6.5 and EC between
0.5 to 0.7 mS/cm respectively.
Proximity to motorable road to take advantages of market for inputs
supply & sale proceeds.
Soil need to be changed or sterilized after every 3 to 4 years
preferably to avoid built up of soil pathogens. Alternatively, artificial
media can be an option for cultivation.
1.1 Site selection
10. Location with respect to highways shall be
considered.
Location on near a highway and residential area
may increase business for a retail operation.
1.2 Location
11. The following points should be considered in
developing a layout for GH structure:
Locate the head house to the north of the GH to reduce
shading;
Locate windbreaks at least 30 m away to the side of the
prevailing winter winds to reduce energy consumption;
Separate supplier & customer traffic;
Provide for convenient consumer parking;
Locate and screen any residence to insure privacy;
Place the outdoor storage area where it is convenient to
access for materials delivery and movement to the
work area
Locate the retail sales area to keep customers away
from the production area to reduce chances for disease
introduction and prevent interruption of work routines
1.3 Site layout
12. Fig. 1: Plan layout of a GH along with other support facilities
13. Correct orientation can provide good environmental
conditions inside the GH. Following points should be
considered while deciding the orientation of a GH
depending upon light intensity and direction & velocity
of wind.
Orientation of the single span GH should be directed
towards East-West.
North - South in case of multi-span for taking advantage
of available sun-shine.
Gutter should be made in North - South direction in
multi span GH.
Slope along the gutter should not be more than 2%.
Wind breaks, should be placed at least 30 meters away
on North -West side of the GH.
1.4 Orientation
14. A headhouse should be built to house the office, utilities, work areas,
employee areas, storage, and dispatch.
This value should be adjusted depending on the indoor storage needed
and the amount of mechanization used.
A good headhouse layout helps the system operate smoothly and
efficiently. Materials flow should be such that there is minimum of
handling or cross traffic in moving the components through the system.
The amount of space needed is determined by the type of operation, kind
of media being used, and the local climate. Calculate space requirements
based on the amount that is needed for one crop or a specific time period.
Locate the storage area for bulk materials and truck loads where there is
good access by all weather road.
The storage should be located close to the work area to reduce handling
time and costs. Provide drainage in the storage area.
Materials stored without cover should drain quickly, provide a paved
area for handling with a bucket loader or fork lift.
A clear span storage building allows freedom of movement for tractors
and trucks and allows arrangement of equipment to be easily changed.
1.5 Head house and storage facilities
15. Table 1: Sizing the Headhouse
GH Size (m2
Approximate Headhouse Area
Needed Per 100 m2 of GH Area
m2
1000 to 3999 14
4000 to 7999 9
Over 8000 7
16. The choice between production on the floor or on the benches
depends on the crop and the production schedule.
Benches are usually provided for pot plant production. Bedding
plants are generally grown on the floor. Beds, either ground or raised
are needed for cut flowers.
Benches may be fabricated of wood, metal, or plastic with a either
solid or mesh bottom.
Benches should be placed at a convenient height above the floor,
usually 500 to 1000 mm.
Benches improve labour efficiency, permit more effective display
and inspection, and assist air circulation.
Bench arrangement depends on dimensions of the GH, walkways &
doors and on materials handling & heating system type and location.
Total aisle space should be less that 25 percent of the total area.
Longitudinal arrangements with benches extending the length of the
house permits continuous runs of water lines, heat pipes, and plant
support systems.
1.6 Interior layout
17. Fig. 3: Cross bedding layout of GH beds
Fig. 4: Longitudinal layout of GH beds
Fig. 2: Peninsula arrangement of GH beds/benches
19. AlI fixed services equipment such as heating,
ventilating, air circulation, electrical, lighting,
watering and energy conservation blankets should
be included if supported by structural members.
Long term crops such as tomatoes & cucumbers
supported by the structure are also considered as
dead loads.
2.1 Dead Load
20. 2.2 Live Load
Live loads are temporary loads and shall include the
mass of repair crews and hanging plants.
The GH should be designed as to resist the snow load.
In area of snow, a minimum distance of 3.0 m should be
provided between GH to allow for snow accumulation
and to prevent side wall crushing from snow sliding off
the roof.
The snow load of GH structures shall be estimated as
prescribed in IS 875 (Part 4).
2.3 Snow Load
21. 2.4 Wind Load
The GH should be designed to resist the wind load.
The wind load of the GH structures shall be estimated as
prescribed in IS 875 (Part 3).
Since the deadweight of most GH structures is very
small, special attention should be given to ensure that
enough ground may be there to resist the upward lift
force created by the wind.
The minimum design loads for the GH, structures
mainframes is given in Table 2 and may be used for
reference only.
Actual design values should be calculated for each GH
structures.
22. Table 2: Minimum Design Loads for GH Mainframes
Load Description
Minimum
Value
N/m2
Dead:
Pipe frame, polyethylene cover
truss frame, lapped glass
supported crops-tomatoes, cucumbers, etc.
100
250
200
Live: workers, repair materials 250
Snow: 10oC minimum GH temperature 750
Wind: load acts perpendicular to surfaces 500
24. Pier foundation may be adequate for primary GH frame, consisting of
hoops spaced one meter or more. A curtain wall can be used to close
the area between the piers. If primary frame members are spaced less
than 1.2 m, a continuous masonry or poured concrete wall should be
used.
The footing should be set below frost level or to a minimum depth of
600 mm below the ground surface whichever is greater. Consult SP 7
building code for local requirements.
It should rest on level, undisturbed soil, or adequately compacted fill.
Individual pier footings should be sized to fit the load and soil
conditions.
The pier may be of reinforced concrete, galvanized steel, treated
wood, or concrete masonry. The wall between galvanized piers can be
poured or precast concrete, masonry, fibre reinforced cement panels,
aluminum clad insulating board, or any moisture and decay resistant
material.
A continuous foundation wall should be set on a poured concrete
footing. The wall can be concrete or masonry.
A 150 mm wall is usually sufficient for building spans up to 7.5 m.
Use a 200 mm wall for wider building spans.
3.1 Foundations
28. Gravel, pea stone and trap rock make a good floor
material. A thickness of 150 to 200 mm is needed for
drainage and weed control.
Where a hard, smooth surface is desired a 50 to 75
mm thickness of porous concrete may be used. This is
made from uniform sized aggregate and a cement
water paste.
Aisles and heavy traffic areas should be concrete.
Thickness depends on the traffic load but usually 75
to 100 mm is sufficient.
Concrete walks should have a broom finish for safety.
Floors should slope to assure surface drainage and be
sufficiently even to prevent puddling.
3.2 Floors
29. Wood, steel, aluminium, and reinforced concrete may be used to build
frames for GH.
Some frames use combinations of the materials. Wood may be painted or
otherwise preserved for protection against decay and also to improve light
conditions within the buildings.
Preservatives shall be used to protect any wood in contact with soil against
decay but they must be free of chemicals that are toxic to plants or
humans. Heartwood has natural decay resistance Wood frames include
post beam and rafter systems, postsand trusses, glued laminated arches and
rigid frames.
Steel and aluminium are used for posts, beams, girts, purlins, trusses, and
arches. Both materials shall be protected from direct contact with ground
to prevent corrosion. White paint on either material will improve the light
reflection in a GH structure.
The rate of heat loss through steel or aluminium is much higher than
through wood, so metal frames may need special insulation. To avoid such
heat loss through steel or aluminium, composite materials are sometimes
used, such as a trussed beam of wood and steel or a member made of
fibreglass reinforced plastic may be used.
Other details for GH Frames (Lecture 5)
3.3 Frames
30. Solarium or attached GH: Connected to a house
Lean-to-GH, attached even-span GH, window-mounted GH
Free standing GH: Separate from other buildings consisting
of sidewalls, end walls, and a roof
Quonset/hoop
Modified Quonset/arch
Gable even span GH
Gable uneven span GH
Connected GH: Several GH joined together
Saw tooth type
Ridge & furrow type or gutter connected
Venlo-Dutch Houses
Barrel vault
3.4 Shape of Structure
Other details for Shape of Structure (Lecture 5)
31. 3.5 Cladding materials
Glass GH
Plastic film GH
Rigid Panel GH
IS 15827:2009 Plastic films for GH-Specification
Other details for GH cladding materials (Lecture 5)
32. Transmission for global radiation (UV and PAR)
Transmission for heat radiation (NIR and FIR)
Insulating effect
Sensitivity to ageing (mainly UV degradation)
Permeability for humidity (water)
Mechanical strength (tensile and impact)
Fire behaviour
Investment costs
Available dimensions
Cladding material properties
33. UV Stabilization
Flexible GH films are usually made from LDPE, LLDPE, EVA and
similar polymers.
In their natural state these polymers deteriorate rapidly when
exposed to sunlight. The sun’s UV light transfers its energy to the
PE molecules causing them to become so energized that they are
readily subject to oxidation.
The degradation process is a series of reactions one leading to
another of which the end products are carbon dioxide and water.
Big plastics manufacturers have begun to produce tough, clear, high
PAR light transmission greenhouse films using hindered amine light
stabilizers (HALS).
Inhibit degradation of PE polymers in GH film without blocking
UV radiation. Stimulate natural bee, bumblebee and other insect
pollination.
34. Diffused film vs Clear film
The incident light can reach the plant as direct radiation or as
diffused radiation.
Diffused light does not allow the shadow formation of the top layers
of leaves to prevent essential light from reaching the lower leaves.
The end result is a facilitation of an effective dispersion of total
light to the darker areas inside the plant volume enhancing
photosynthesis and hence the production of biomass.
Break sun radiation into a multitude of rays, optimizing the even
spread of light within GH, which: Increases efficiency of
photosynthesis when covered areas of self-shading and trailing
plants receive light, decreases phototropism, decreases potential for
sunburn on blooms and leaves.
35. UV Blocker
Block UV sun rays (up to 380 nm): Causing insects to lose visual
ability inside GH, preventing viral, fungal diseases and crop
damage caused by white flies, aphids, red spiders, leaf miners,
thrips and other insects, resulting in substantial decrease in
dependence, on and use of agricultural chemicals, contributing to
Integrated Pest Management (IPM) programs. Disease control
films should not be used in GH requiring insect pollination
Blackening (or petal discoloration) of red roses is a major problem
for the rose growers. This phenomenon is caused by the UV
radiation acting together with low temperatures. A crop under UV
blocker film does not experience blackening of rose petals.
36. Infrared (IR) Additive
Minimize temperature fluctuation:
During the day, slightly decreases temperature inside GH by
blocking near infrared radiation (NIR: 700- 3000 nm). It is the part
of the solar spectral that is hardly used by the plants for
photosynthesis; it is mostly substituted into heat (sensible and
latent) in the GH. This can be an advantage in a country with a
colder climate and a disadvantage in a GH located in warm country.
During the night, increases temperature inside GH, by creating a
barrier to far infrared radiation (FIR: 3000-100000 nm) reflected by
the soil. It is not caused by direct sun radiation, but it is heat
radiation transmitted by each heat body in and on the GH. This
radiation is very important in GH; since it causes a part of the
greenhouse effect.
37. Anti-Dust Additive
Facilitate the removal of dust, soil and dirt
stuck on the outer GH surface with rain or a
simple wash.
Prevent decrease in the amount of light
transmitted through the GH cover.
An anti dust layer is always on the upper side
of the plastic. It is very important to note that
anti dust side must be facing outside.
38. 3.6 Roof Slope
Roof slope is an important parameter in GH design.
The maximum amount of light energy transmitted occurs when the
glazing surface is perpendicular to the solar rays.
Transmission of solar radiant energy is determined by the angle at
which solar rays strike the GH surface.
Figure 9: The effect of angle of incidence on transmission of solar radiant energy through GH glass
39. 3.7 Influence of Interior GH Components and Systems
With the advent of thermal screens, supplemental lighting and other
GH handling systems along with traditional overhead heating
systems concern has been expressed for obstruction of PAR lighting
which is caused by these overhead mounted components of the
growing system.
Under bench heating and in-floor heating systems have reduced the
number of overhead heating pipes necessary to meet the demand
load.
Thermal screens which are installed and move gutter to gutter can
reduce shading because the thermal screen shares the shadow
pattern with the shadow caused by the structural gutter and does not
add an additional shadow which is caused by the system which
moves from truss to truss.
There has been an attempt to reduce the size of supplemental
lighting fixtures to reduce the shadow patterns they produce. The
grower must be concerned with the adoption of new practices which
add significant overhead components.
40. 3.8 Size
The size of the GH needs to be selected based on
availability of the land.
The cost may vary depending upon the types of GH and
number of suppliers present in the region.
Depending upon the market access and experience of GH
cultivation, it is suggested to start with a naturally
ventilated GH having minimum size of 100 sqm as it
would require less initial capital investment along with
operational expenditure.
However, experienced farmers/entrepreneurs may decide
to go for larger size GH depending on their scale of
operation and project costs.
41. 3.9 Height
Height is one of the most important aspects of GH design
and it directly impacts natural ventilation, stability of the
internal environment and crop management.
The ideal centre height of naturally ventilated small GH
(up to 250 sqm) should be in the range of 3.5 m to 4.5 m
and 5.5 m to 6.5 m in case of large size GH.
The side/gutter height should be in between 2.5 m to 3 m
and 4.5 m to 5 m for small and large size GH respectively.
Both types of GH can be made in single or multi-span
structures.
A multi-span GH can be constructed for an area more than
200 sqm and is economical in terms of construction
material & required control/monitoring equipments.
Height of the GH having fan & pad cooling system should
be slightly lesser than the naturally ventilated greenhouse
and in any case not be more than 5.5 m.
43. 4.1 Fire Safety
Fire safety is important in selection & use of glazing
materials.
Flammability of plastic materials when exposed to an
igniting source shall be as prescribed in IS 11731 (Part 1
and 2 ).
4.2 Mechanical Safety
There shall not be any projections of sharp points or
edges which may cause cuts/lacerations.
Adequate guarding against entrapment of limbs in
moving and stationary equipment shall be provided.
44. 4.3 Electrical Safety
There shall be no breakdown of insulation and current
leakage in from electrical fittings inside the GH.
GH frame shall be protected from contact with parts
normally at hazardous voltage.
4.4 Chemical Safety
Inside the GH there shall he full protection against
potential injury or damage to health resulting from
inhalation, ingestation or contact with harmful
chemical agents.
46. 5.1 Electricity
An adequate electrical supply and distribution system should be
provided to serve the environment control & mechanization needs
of the GH.
To determine the size of the services, the size and the number of
motors and other electrical components should be known.
Provisions should be made for an alarm system to indicate when a
power failure has occurred or an environment control system has
failed.
An auxiliary generating system should be available and installed
with the proper transfer switch to prevent feedback of power to the
utility lines.
Utility lines should be buried to improve appearance, avoid damage,
and reduce hazards.
Electric, phone, and fuel lines should be buried at least 500 mm
deep to avoid damage from surface traffic.
Location of the utility lines should be recorded on a map for future
reference.
For distribution system within the GH structure, the National
Electrical Code may be taken in account.
47. Table 4: Electrical Power Requirement for GH of different
size (Chandra, 1992)
GH size (m2) (amp/volts) Electrical power
requirement
500 60/240 15
500 – 2000 100/240 24
2000 – 3000 150/240 36
3000 – 4000 200/240 48
4000 – 8000 400/240 96
8000 – 12000 600/240 145
48. 5.2 Watering
The amount of water requirment depends on the water requirement
of the cultivation medium, area to be irrigated, crop grown, weather
conditions and whether the heating and/or ventilating system is
operating.
Details for irrigation systems in GH (Lecture 9)
Table 5: Estimated Maximum Daily Water Requirements
Crop
Water Required
litres/m2
Bench crops 16.0
Bedding plants 20.0
Pot plants 20.0
Chrysanthenum 41.0
Roses, tomatoes 29.0
49. The water system for the GH should have the capacity to
supply the total daily needs in a 6 hour application period.
This allows the plants to be watered during the morning and
early afternoon and with time for the foliage to dry before
sunset.
Ground water is usually the most reliable source of water. It is
available from drilled wells, dug wells, etc.
Surface water ponds, lakes and streams may also be used, but
precautions shall be taken to insure against contamination
injurious to the plants.
Irrigation water may contain impurities that adversely affect
the growth of the plants. Therefore, quality of the water shall
be ensured before irrigation.
Micro irrigation system is the most suitable method for
irrigation to the GH crops. The quality of irrigation water shall
conform to IS 11624.
50. 5.3 Climate Control System in GH
Cooling of the GH is necessary wherever the outside temperature goes
beyond 30°C and also when temperate crops are to be grown.
Depending upon the glazing material and the ventilation, once the GH
structures are covered the inside temperature may be at least 5 to 10°C
higher than the outside temperature, if it is not cooled. In order to create
better growing conditions, it is necessary to cool the GH structures.
Heating required in places where the winter temperature is very low.
Similarly, in places where the climate is extreme cold and warm, both
cooling and heating are required at higher elevations, where
temperatures do not normally go above 30°C, cooling may not be
necessary, only providing proper ventilation will serve the purpose.
However, these places may require heating during winter for successful
crop production.
Heating, ventilating and the cooling of the GH structures shall be
done as prescribed in IS 14485:1998.
Details for cooling & heating of GH (Lecture 8)
51. If you have any question/suggestion
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