Plexiglass, a common trade name for polymethyl methacrylate (PMMA) acrylic sheeting, is a popular alternative glazing material for greenhouses. The development of plastics like acrylic and polycarbonate introduced options that balance strength, clarity, and cost, moving beyond traditional glass. Acrylic presents a compelling middle ground between the fragility of glass and the superior toughness of polycarbonate. Evaluating its suitability requires a close look at how it manages the light and heat plants need to thrive, alongside its practical lifespan and installation requirements.
Plexiglass Performance: Light Transmission and Thermal Efficiency
Acrylic boasts exceptional optical clarity, transmitting a very high percentage of visible light, often reaching up to 92% of Photosynthetically Active Radiation (PAR). This high transmission rate is comparable to standard horticultural glass, making it highly effective for maximizing photosynthesis. The material is naturally UV-stable and resists yellowing more effectively than some untreated plastics, maintaining high light clarity over a long service life.
Standard acrylic inherently blocks most harmful, short-wavelength ultraviolet (UV) radiation, protecting both the plants and the material. However, specialized acrylic products are available that transmit the full spectrum of light, including UV, which some growers prefer for promoting specific growth characteristics like vibrant bloom color. A single pane of Plexiglass offers only modest insulation, though it is an improvement over single-pane glass. To achieve better heat retention, acrylic is often manufactured in multi-skin or multi-wall configurations, creating insulating air pockets that significantly increase its R-value.
Durability and Maintenance Considerations
Plexiglass exhibits significantly greater impact resistance compared to traditional glass, being approximately 17 to 20 times stronger and far less prone to shattering from hail or debris. This resilience offers a safety advantage over glass, though it does not match the virtually unbreakable nature of polycarbonate, which can be up to 250 times stronger. The primary drawback of acrylic is its vulnerability to scratching; its surface is easily marred by abrasive materials, potentially clouding the material and reducing light transmission.
High-quality acrylic is naturally UV-stable and resists the yellowing that plagues many plastics, though untreated or lower-grade sheets can still degrade over decades of sun exposure. Many manufacturers offer non-yellowing guarantees, with acrylic’s expected lifespan often reaching 30 years before significant degradation. For cleaning, users must strictly avoid harsh chemical cleaners and abrasive cloths, as these damage the surface finish and compromise clarity. Mild soap and water with a soft cloth are recommended to maintain the optimal transparency of the glazing.
Cost and Installation Logistics
The cost of Plexiglass positions it in the mid-range of greenhouse glazing materials, typically falling between standard glass and the higher expense of premium, multi-wall polycarbonate sheeting. Its moderate price point makes it an appealing choice for hobbyists seeking a durable upgrade. The material’s lightweight nature is a major logistical advantage, weighing about half as much as glass and simplifying transportation and on-site handling.
Installation is easier for do-it-yourself builders because the light panels require less robust framing compared to heavy glass. Acrylic is also easy to cut and shape on-site to fit custom frame dimensions, which streamlines the construction process. Care must be taken during framing, as acrylic is more rigid than polycarbonate and can crack if handled roughly or drilled incorrectly. Proper sealing and allowing for thermal expansion are necessary to ensure the panels remain secure and watertight.