How Greenhouses are constructed
Modern greenhouses are steel structure with a transparent cover. Shapes
as follows. In California we generally use plastics rather than glass.
Greenhouse structure:
- Various styles
- lean-to:
- single span
- ridge and furrow
- A-frame
- Quonset (plastic glazing)
- high-profile
vs low-profile
- Support structure: wood aluminum steel
- stronger materials can be spread farther apart - less light loss
Greenhouse glazing material:
- Criteria for electing glazing material:
- heat versus light penetration
- can they tolerate the forces of the environment: snow, wind
- fire hazard
- construction costs / maintenance costs
- life expectancy
- condensation / light environ. & dripping on plants
- glass
- the only material used prior to 1950
- heavy - requires lots of structure
- expensive
- very durable
- its now possible to get large panes so light interception is less
serious problem
- double-paning is possible - obviously even more expensive
- films
- polyethylene
- cheap to buy (cost effective for do-it-yourself)
- short life (3 years)
- with various filters (3-5 years)
- good light penetration when new
- double layering - inflate with fan (use air from outside)
- problems with crud between layers
- frequent replacement represents high labor (maint. cost)
- rigid panels
- fiberglass-reinforced panels
- acrylic and polycarbonate