This document discusses different types of greenhouse coverings including glass, plastic films, and double layer options. Glass greenhouses can be made with annealed, tempered, or laminated glass but have higher costs. Film plastic like polyethylene is a common low-cost option in India. Double layer coverings provide improved insulation over single layers. Gutter-connected and quonset designs are described for plastic film structures.

1. FILM PLASTIC GREEN HOUSE-
GLASS HOUSE-
GREEN HOUSE WITH DOUBLE LAYER
COVERING

2. GLASS GREENHOUSE
• Glass as glazing materiel
• High light transmission
• Higher air infiltration
• High initial cost
• Low thermal resistance- high heating cost

3. • 3 type glasses
1. Annealed glass
• Cheapest glass
• very weak and prone to cracking
• Broke into sharp pieces

4. 2. Tempered glass
• Heat-treated glass
• Very clear
• six times stronger than
annealed glass
• Expensive than annealed type
• Broke into granular pieces

5. 3. Laminated glass
• Two or more sheets of glass bonded using
ethylene-vinyl acetate (EVA) or polyvinyl butyral
(PVB)
• Do not break
• Block 99% UV radiation
• Resistant to high load
• Highly expensive

7. Single Pane Glass
• Low energy efficiency
• High heating cost
• Glass 3mm -Light transmission - 95%
- R-Value- 0.96

8. Double Pane Glass
• Energy efficient
• Low heating cost
• “Low-E” reflective coating
on the inner pane of
glass- insulator
• Double Glass 16mm- R Value -2.1
-light transmission -90%
• “Low-E” glass - R Value- 3.45
-light transmission- 70%

9. Designs for glasshouse
• Lean-to type
• Even span type
• Ridges and furrow type
-Less working cost
-Energy efficient

10. Ridges and furrow type greenhouse Even span greenhouse

11. Sash bar

12. FILM PLASTIC GREEN HOUSE
• Flexible plastic films- polyethylene,
polyester, polyvinyl chloride, polyvinyl
fluoride
• Polyethylene- since 1930s
• Most common type in India

13. Advantages
• Easier for covering- less time, less labour
• Low initial cost
• Cost of heating-40% lower than single layer
glass and FRP greenhouse
• Low cost of management

14. Polyethylene
• Most popular
• Thickness -200 micron
• Transmittance- 88-89%
• Susceptible to UV light-
-reduce light transmission
-become brittle
• polyethylene - 1-2 year

15. Cont…
• UV stabilized polyethylene -3-4 year
• Condensation of vapour on film
• Thermal resistance incorporated by IR
blocking chemicals

16. Polyvinyl chloride
• 8 mil - 4 year
• 12 mil – 5 year
• Transmittance-86%
• Vinyl film-static charge –attract dust-reduce
light transmittance
• Costlier than polyethylene

17. Polyester
• Higher life
• 5 mil on roof – 4 year
• 3 mil on wall – 7 year
• High light transmittance- same as glass
• Free from static electricity
• Heat retention curtains- capacity to block
radiant energy

18. Polyvinyl fluoride(PVF)
• Life- 10 year or more
• Light transmission- 4 mil- 92%
• 4 mil PVF- tensile strength-4 times of 6 mil
polyethylene

19. • Film plastic greenhouse designs are mainly
of two styles
1. Quonset-style greenhouse
2. Gutter-connected green house

20. Quonset-style greenhouse
• Less expensive
• Trusses- 0.75 inch pipe for 20 feet wide
greenhouse
-1 inch- 30 foot wide greenhouse
• Trusses - 30-36 inches apart
• Width of covering material -32 feet for 20
feet wide greenhouse
-40-42 feet for 30 feet greenhouse

21. Cont…
• Wooden frame- film is nailed to frame
• Metal frame-metal channel lock screwed to
frame –film tightened in it using wiggle wire

23. Gutter-connected greenhouse
• Gutter -12-40 foot apart
• Columns –in each or alternate gutter
-11 m row spacing
• Minimum exposed surface area-low heating
cost
• For 17 foot wide bay- 20 foot wide film

25. Greenhouse with double layer
covering
• Two layer film –dead space, in between
• Supporting upper layer-plastic strips, wood
strips ,metal channel lock
• 2 layer-outer layer 6 mil, inner layer 4 mil
• Squirrel cage fan- to inflate the space
between two layer (49-68 Pa)

26. Squirrel cage fan
metal channel lock

27. Advantages
• High energy efficient
• Improved insulation properties
• Light transmission can be controlled