Greenhouse Structural Materials
Greenhouse can be constructed from several types of materials including aluminum, galvanized steel and wood. There's a wide selection of commercial greenhouse framing materials available. Plastic materials are not the best framing material and often fail to meet the minimum snow and wind load requirements.

Greenhouse Frames
The deciding factor in selecting a greenhouse frame is engineering requirements and personal design ideas. Below are several common greenhouse frames.

• Quonset - Low sidewall height restrict storage space and headroom, however, construction is simple. Electrical conduit or galvanized steel pipe frame
  
  

• Gothic - Construction is similar to the Quonset but with a different structural shape and allows more headroom at sidewalls. Wood arches can be used and joined at the ridgeline.
  
  

• Rigid-frame - Gable roof and sidewalls allows maximum interior space and air circulation. Requires a soild foundation to support the laterial load on the sidewalls. No columns or trusses to support the roof. Clear-span construction utilizing vertical sidewalls and rafters.
  

• Post and rafter - Simple construction utilizing embedded post and rafters, requires more structural materials such as wood or metal than other designs. Requires sturdy, deeply embedded posts to tolerate outward rafter forces and wind pressure. Allows more space along sidewalls. Efficient air circulation.
  

• A-frame - Similar to post and rafter, however, a collar beam joins the upper part of the rafters

Greenhouse Coverings
The type of covering used must correspond with the type of frame used. Different coverings have different lifespan. Film plastic have a 1-3 year lifespan. Other types of coverings includes glass, rigid double-wall plastics and fiberglass.

• Glass - Traditional greenhouse cover material. Inexpensive to maintain. With combined with an aluminum frame, glass is easily maintained with a weather proof structure that minimize heat cost and reatins humidity well. Glass is a flexible cover option as it's suitable of almost any style frame. Tempered glass is two-three times stronger than reqular glass. If using glass, have the manufacturer build the greenhouse as they can be difficult to DIY (Do it Yourself).
  
  Glass is a great option, however, it's start-up cost can be expensive, requires solid frame and foundation to support the heavy glass covering.
  
  

• Fiberglass - Lightweight, strong material. Only strong, clear, high-grade fiberglass is recommended because lower grades discolor and reduce light. Tedlar-coated fiberglass may last up to 20 years. A new coat of resin should be applied after 10-15 years to maintain light penetration and prevent dirt and residues from building up on fiberglass.
  
  

• Double-wall plastic - Double layer sheets of plastic acrylic or polycarbonate. Long-life, energy-saving rigid covering seperated by webs. Acrylic is long lasting covering that do not yellow easily. Polycarbonate yellows faster than acrylic, however, it's protected by a UV protector coating. Each sheet or layer of plastic will reduce light by up to 10%.
  
  

• Film plastic - available in various grade, quality and material. Requires more frequent replacement than other cover options. Low structural cost because it dosen't require a heavy frame. Additionally, plastic film is inexpensive, making start-up cost relatively low compared to the previous options. 
  
  Made from polyethylene (PE), polyvinyl chloride (PVC), copolymers and other materials, film plastic offers comparable light penetration to glass.
  
  Although film plastic cost less than other options, they need to be changed more frequent. Utility grade PE will last about a year and has UV inhibitor to protect against UV Rays and last about a year and a half.
  
  PVC or vinly film cost up to 5 times as much as PE, however, they may last up to 5 years. They do, however, attract dirt and needs frequent cleaning.