November 08, 2013

What is Better to Build a Glass or Polycarbonate Greenhouses?

Which is the Best Choice, of Greenhouse Building & Construction Planning, Glass Greenhouse Plans or Polycarbonate Greenhouses Plan?

Post Category: Greenhouse Articles > Building Greenhouses > Greenhouse Components & Parts > Glass and Polycarbonate > Material and Cost Comparison

Greenhouses are classically made from aluminum and glass, but recently, some people are substituting the glass for twin wall polycarbonate.
  • The mega trend toward producing your own vegetables is leading more growers to experiment with different materials and expand beyond traditional options.
  • Plastic greenhouse construction materials include fiberglass, polyethylene film, and polycarbonate.

Polycarbonate has numerous advantages over glass, including:

1. Greenhouse Insulation Ability:

Successful greenhouse plant growing is a matter of keeping the plants at the right temperature.

  • Glass is not a very efficient material when it comes to heating, because it transmits heat and cold too rapidly.
  • People have made use of glass’s difficulty retaining heat in other structures, from thermometers to spoons, but it is a disadvantage in other areas.
  • Greenhouse glass panels are usually double or triple the normal thickness of glass to provide enough insulation, which can be problematic.

Manual Polycarbonate Greenhouse Window and Vent Opener Picture

At the right thickness, polycarbonate sheets retain heat better than horticulture glass.

  1. Polycarbonate sheets can lengthen the plants’ growing season, which can make all the difference in plant production.
  2. Twin polycarbonate sheets are structurally similar to thermal windows, and provide a similar benefit.
  3. They can reduce heating costs when compared to glass-paneled greenhouses, due to their greater heat retention abilities.

Polycarbonate Greenhouse Glazing on Basic EarthCare 6x8 Greenhouse Picture

A material’s thermal insulation value is its ‘R’ value: Horticulture glass that’s three millimeters thick has a lower R-value than four-millimeter twin-wall polycarbonate sheets.

Single layer polycarbonate sheets have a reduced R-value compared to glass, so it is important to take grades and measurements into account, and not to substitute single layer polycarbonate sheets for twin layer polycarbonate sheets.
  • A higher R-value can make all the difference for the plants, particularly when growing during the autumn and winter.
  • The R-value will increase in proportion to the thickness of the twin panel polycarbonate walls.

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2. Greenhouse Structural Durability:

Glass is famously fragile. 

  1. Polycarbonate sheets can withstand far more pressure and shocks than glass, including fallen tree branches, hail, heavy storms, and the impact from incoming tennis balls.
  2. Growers with nearby trees, active wildlife, or bustling neighbors may want to invest in polycarbonate sheets.
  3. Twin polycarbonate sheets are also highly flame resistant, in case of emergencies.
  4. On average, twin polycarbonate sheets last for fifteen years under ideal conditions.
  5. Greenhouses made from glass require substantial repairs over the course of their own lifetimes.
Pretty Pink Flowers Growing Wild in a Commercial Glass Greenhouse

3. Ease of Greenhouses Assembly:

Polycarbonate sheets are not as heavy as glass, and do not have to be cut specially to fit the greenhouse specifications. 

Glass is heavier than many other building materials, and needs the sort of significant framing structure polycarbonate sheets do not. Glass also must be kept completely rigid during construction. Often times, amateur growers cannot construct glass greenhouses themselves, and must procure the services of a contractor. Polycarbonate sheets are more conducive to individual assembly.
EarthCare Grow Wise Double Cold Frame Greenhouse: Available at

4. Internal Light Penetration:

There is a risk of burning plants when using glass-paneled greenhouses, because glass does not effectively diffuse light.

  1. Polycarbonate sheets are constructed to have a ribbed texture that breaks ultraviolet rays.
  2. The texture of polycarbonate sheets diffuses the incoming ultraviolet light, all the better for plant growth.
  3. The diffused light minimizes shadow, so growers can take full advantage of incoming light and not have to compensate on behalf of the plants.
  4. Some plant species need more or less light, and could be most efficiently grown in a greenhouse made from twin-walled polycarbonate.
Internal Twin-Walled Polycarbonate Greenhouse Light Difusion R Value
Fully Built and Constructed Glass Commercial Greenhouses Picture
Materials: Made with Glass

5. Reduction in Inside Greenhouses Condensation Levels:

Twin polycarbonate sheets have been tested in conditions of eighty percent humidity, with a fifty degree temperature differential between the outside and the inside of the greenhouse.

  1. There was still no condensation on the greenhouse glass. 
  2. Greenhouse condensation is more important in regards to aesthetics, but a buildup of moisture can still be problematic.
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Growers can also take advantage of both materials, and get greenhouses constructed from a combination of glass and polycarbonate.
  • Some growers still prefer glass greenhouses for sentimental reasons.
  • Advances in materials science will create a portfolio of options for greenhouse growers and hobbyists.

Garden Earth Worm Soil and Grass Compost Picture

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