By Alina, Project Engineer, Ziyang Bozong Greenhouse Industry Co., Ltd.
That number is correct, and on its own it is nearly useless.
Why? Because the two ends of that range are decided by things you control, not by the film you bought. The same roll of film can fail in year three on one farm and still be working in year six on another. We have shipped film into more than 30 countries, and the climate is only part of what separates those two outcomes.
So the question worth asking is not how long film lasts. It is what is consuming the film on your site, and which of those things you can slow down. The rest of this page follows the film through its actual life: choosing it, installing it, living with it, and knowing when to replace it.
Three families of film get sold for greenhouses.
| Type | Construction | What it is good at |
|---|---|---|
| PE (polyethylene) | Base film with UV stabilizers | Widest price range, most common |
| EVA (ethylene vinyl acetate) | PE with EVA layers | Better light transmission, better heat retention |
| PO (polyolefin) | Multi-layer, often five layers | Best balance of transmission, strength and lifespan |
The mistake we see most often is comparing film on price per kilogram. A film that costs 30% less but lasts two years instead of four has not saved you money. It has bought you an extra replacement cycle and two years of lower light levels that nobody notices until harvest.
Multi-layer construction is where most of the real gain sits. On our gothic multi-span houses, the covering is a three-layer extruded film. The outer layer is formulated to shed dust, the inner layer is anti-dripping, and UV blocking is built into the film itself. Those are three separate problems, and they need three separate layers.
Thickness matters too, but less than people expect. A common commercial range runs from about 150 μm to 200 μm. On our smaller sunlight houses we supply 0.12 mm and 0.15 mm film, because those houses are usually used for a single crop cycle in a cold season. On a commercial multi-span house we agree the thickness with the customer rather than defaulting, because going up a thickness step is a small one-off cost against several extra years of use.
Most premature film failures we are asked about trace back to the week the film went on, not to the film itself.
Tension is the first thing. Loose film flaps. Flapping film fails at every point where it touches the frame, and it fails fast. A properly tensioned cover does not move in normal wind. This is why we fit a locking profile rather than clips on our frames: it holds tension far better over a season of thermal cycling.
The second thing is the frame surface. Run your bare hand along a frame before the film goes near it. If anything snags your skin, it will do worse to film over thousands of wind cycles. Weld spatter and sharp cut edges act like a grater, and rough galvanizing in a joint is often the last thing anyone checks.
The third is separation. Anywhere metal meets film directly, use tape or padding. Contact points are where wear starts, and padding them costs almost nothing.
Ultraviolet light. This is the primary cause of death. UV breaks the polymer chains, and the film turns brittle, discolours and then tears. Good film contains UV stabilizers, but those stabilizers are consumed as the film works. When they run out, the film goes quickly. That is why film often looks fine in the morning and shreds in an afternoon.
Heat. Interior temperatures above 40 °C are routine in summer. Heat accelerates the chemistry that consumes both the polymer and the stabilizers. A greenhouse in a hot climate simply uses up its film faster than the same house in a temperate one.
Wind. Film expands in the heat, contracts at night and flexes in every gust. Each cycle is a small mechanical load. Loose film multiplies it.
Chemicals. Sulphur-based fungicides and some fertilizers attack polyethylene. Where sulphur vaporizers are used, film life can drop sharply, and the cause is easy to miss because the film looks otherwise sound.
Most growers replace film when it tears. By then they have already lost months of production.
Film does not degrade evenly. It starts near 90% light transmission and drops as it ages, and the drop accelerates. A three-year-old film is passing noticeably less light than a new one, which means slower growth and lower yield well before the first hole appears.
There is a simple test that costs nothing. Keep one offcut of new film from the last installation. Once a year, hold it up against a panel that has been in service, in daylight, and compare. When the difference becomes obvious, the film is already costing more in lost production than a replacement cover costs to buy.
We are a factory in Ziyang, Sichuan, and we have been building greenhouses for more than 35 years. The site covers over 180,000 m² and employs 378 people, including 18 design engineers who lay out the houses and 35 installation engineers who travel to project sites.
Two choices we make on every film order.
The first is anti-dripping treatment on the inner face. Without it, condensation forms as droplets that fall onto the crop and onto the frame. Every drip is a wet leaf, and wet leaves are where fungal disease starts. Anti-drip is not a cosmetic upgrade for a hot or humid market. It is a disease management decision.
The second is UV blocking specified as a treated film, not as a claim. A supplier who tells you their film is UV resistant but cannot say how the stabilizer is loaded is telling you the film will hold long enough to be sold, and no longer.
If you are planning a greenhouse and want to know what film specification makes sense for your climate and crop, tell us your location, your crop and the months you need cover. We will tell you what we would specify, including the thickness we would not go below and why.
Alina, Project Engineer Ziyang Bozong Greenhouse Industry Co., Ltd. — Sichuan, China
