Journal · 2026.06 · 9 min

Film, Netting, or Glass — Choosing the Right Greenhouse Covering

The covering defines a greenhouse’s light, temperature, and budget. Poly film is affordable and fast to install, netting ventilates and excludes insects, glass transmits the most light and lasts the longest — there is no absolute best, only what fits your crop and business.

Most people’s first question about covering is “which one is best?” — but there is no best covering, only the right one. Film is cheap and quick to replace, glass transmits light and lasts for decades, netting ventilates and keeps pests out; the difference isn’t quality, it’s how you plan to run the greenhouse.

The frame determines whether a greenhouse stands; the covering determines how light, heat, and moisture move in and out — directly affecting crop performance and running costs. An international literature review puts the solar transmissivity of glass at roughly 75–92% and of PE film at 70–89% — close on light alone; what really separates them is durability, insulation, and cost.

Film is light, affordable, and quick to install, conforming to arched and irregular roof shapes — making it the most common covering in Taiwan and across Asia. Its weakness is lifespan: under intense UV and typhoon wear it needs periodic replacement, so long-term operators must budget for re-covering labour, material, and downtime. And “film” is not a single material — choosing the wrong grade can cost years of service life:

• PE (polyethylene) film: the most common and cheapest, typically replaced every 1–3 years. Always specify UV-stabilised agricultural grade — otherwise it degrades much faster under Taiwan’s sun.
• PO (multi-layer co-extruded polyolefin) film: higher light transmission and mechanical strength, usually with anti-drip and anti-dust surface treatments; service life commonly 3–5+ years. Costlier per square metre, but with fewer re-coverings the long-term cost can beat PE.
• EVA film: better heat retention than PE — suited to crops that need warm nights; the trade-off is a surface that attracts dust, so watch for transmission loss.
• Functional films: diffusing (matte) films spread light more evenly and reduce leaf scorch at the canopy top; UV-blocking films suppress some pathogens and pests — but can also affect bee pollination and fruit colouring, so match them to the crop.

Netting doesn’t aim for enclosure: the mesh keeps out pest vectors, strong wind, and hail while preserving maximum natural ventilation. In a hot, humid subtropical climate a net house is often more practical — and cheaper — than a closed greenhouse for leafy greens and fruiting vegetables. The trade-off: temperature and humidity cannot be precisely controlled, and rain protection is limited. And netting has grades of its own — the wrong mesh count keeps out the pest but cooks the crop:

• Insect netting is specified by mesh count: the higher the count, the finer the holes. 16-mesh stops whiteflies and larger insects with the best airflow; stopping thrips takes 24–32 mesh, which sharply increases airflow resistance — so it must be paired with larger vent openings or forced ventilation, or heat build-up will hurt the crop.
• Shade netting is specified by shading rate: commonly 30–70%, matched to crop light needs and season. Black net is cheap and durable; silver-grey net also reflects light to repel aphids.
• Material and weave: mostly UV-stabilised HDPE; lifespan and wind resistance depend on thread gauge and weave. Typhoon-season experience: failures usually start not in the net itself but in the fixing and edge details.

Beyond the usual plastic netting, stainless-steel insect netting is worth considering in rodent-prone areas. Woven from very fine metal threads, it far outperforms plastic on rodent- and bite-resistance and on durability — and although it costs several times more upfront, it can be the better value where animal damage is a real threat. A side-by-side comparison:

Glass transmits the most light and, unlike plastics, doesn’t yellow or degrade under UV — its service life is measured in decades, which is why Dutch Venlo greenhouses use it as standard. Glass has grades too: the literature notes that glass absorption depends mainly on iron content, so higher-transmission low-iron glass is the premium option, while diffused (matte) glass scatters light evenly and reduces scorch at the canopy top; tempered glass is the norm for safety. The cost: the highest price and structural demands of any covering. Glass is heavy, so frame and foundations must be strengthened, and installation tolerances are tight. It suits growers who treat the greenhouse as a long-term production asset with year-round climate control.

Hwa-Nan will never know your crop better than you do, and engineering should never dictate farming. Our role is to model, at the planning stage, the up-front and long-term costs of different covering combinations for your crop and site — filling in the pitfalls only visible from the engineering side, while every growing decision stays with the person who knows the crop best: you.

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