Greenhouse Covering Materials Compared: Film, Polycarbonate, and Glass

The covering is the largest single surface of any greenhouse, and it decides how much light reaches the crop, how much heat escapes at night, and how often you will be replacing materials. Choosing wrong means years of high energy bills or a covering that fails after a single harsh season. We supply the lock channels, springs, film clamps, and hardware used to mount and tension greenhouse coverings worldwide, so we see every type of covering in daily commercial use. This comparison covers cost, light transmission, insulation, and lifespan, so you can match the material to your climate and budget.

What Defines a Good Greenhouse Covering

Four properties matter most. Light transmission determines photosynthetic potential — PAR light in the 400 to 700 nm range is what plants use, so a covering that transmits 90 percent PAR outperforms one that transmits 80 percent regardless of how bright it looks. Insulation value, expressed as a U-value, controls nighttime heat loss; lower is better. Durability sets the replacement interval, and diffusion matters because scattered light penetrates the canopy deeper than direct sunlight. Finally, UV stabilization determines how quickly the material degrades under sunlight — the most common reason cheap film fails early.

Polyethylene Film — Affordable and Versatile

Polyethylene (PE) film covers the majority of commercial greenhouses worldwide because it is inexpensive, lightweight, and easy to install and replace. Good quality UV-stabilized film lasts three to five years, transmits roughly 85 to 90 percent of light when new, and, in double-layer inflated form, provides insulation comparable to rigid panels at a fraction of the cost. The weak points are lifespan and wind resistance — flapping film abrades against the frame and fails at stress points. That is why proper tensioning hardware matters: lock channels and springs, like the card lock and spring sets we manufacture, hold film firmly and make replacement a fast, two-person job rather than a full-day struggle.

Polycarbonate Panels — Durable Multi-Wall Construction

Twin-wall and multi-wall polycarbonate panels are the standard for long-life hoop houses and greenhouse side walls. A 6 mm twin-wall panel transmits about 75 to 85 percent of light while providing roughly double the insulation of single-layer film, and panels typically last ten to fifteen years with a UV-protected coating on the sun-facing side. Polycarbonate shrugs off hail and wind, which makes it popular in storm-prone regions. The downsides are higher upfront cost and gradual yellowing and loss of transmission over a decade. Installing panels with the UV side facing outward and sealing the channels properly prevents premature degradation.

Glass — Maximum Light and Longevity

Glass remains the premium covering for high-value crops because it transmits over 90 percent of light, does not yellow, and lasts twenty-five years or more when properly glazed. Tempered or laminated safety glass resists hail, and aluminum glazing bars hold panes securely. The trade-offs are weight, which demands a stronger frame, and poor insulation unless double glazing is used — standard single glass loses heat rapidly at night. In cold climates, glasshouses pair with thermal screens to offset this. For growers who plan decades of operation and need maximum winter light, glass often wins the long-term cost comparison despite the initial investment.

EVA and Co-Polymer Films — Enhanced Performance

Beyond standard PE, specialty films improve specific problems. Ethylene vinyl acetate (EVA) and co-polymer films offer better elasticity, puncture resistance, and anti-drip behavior. Anti-condensation films contain surfactants that spread condensation into a thin layer instead of dripping droplets onto the crop — important for disease control in humid climates. IR-blocking films reflect long-wave radiation back into the house at night, raising nighttime temperatures by 1 to 3°C and saving meaningful heating fuel in winter. Three-layer co-extruded films combine UV stabilization, anti-drip, and IR blocking in one product, and while they cost more per square meter, their longer life and energy savings often reduce the true cost per year.

Matching Covering to Climate Zone

Climate should drive the decision. In cold northern regions, double-layer inflated film or multi-wall polycarbonate cuts heating costs dramatically; glass without thermal screens is hard to justify. In hot, sunny regions, prioritize high transmission only if you can also shade — otherwise combine a moderate-transmission covering with ventilation and shade cloth. In coastal or hail-prone areas, impact resistance and wind anchoring take priority, favoring polycarbonate or glass with strong clamps. And in every climate, remember that the covering is only as good as its attachment: budget for quality lock channels, springs, and edge seals from the start, because a poorly secured covering fails early no matter which material you choose.