TECHNICAL 10 · COVER

Film selection: thickness, UV life and the three grades that matter.

Film is a consumable. The frame is bought once; the cover is bought every few years, and the grade decides how often. The structural consequence is fixing detail and purlin spacing, not steel size.

Grades a buyer will be offered
Grade	Typical thickness	What it does	Where it is used
Standard UV	150–180 μm	UV stabilised, 3–4 season life	Season extension, tunnels
Heavy UV	180–200 μm	Longer UV life, stronger mechanical	Multi-season, windy sites
Thermal / IR	150–200 μm	Reduces heat loss at night	Cool-climate houses
Anti-condensation	150–200 μm	Additive reduces droplet formation	High-humidity, disease-sensitive crops
Diffused	150–200 μm	Scatters light, reduces leaf burn	High-light sites

Life figures are supplier claims, not ours. Ask for the UV stabiliser content and the manufacturer's warranty.

What film does to the frame

Purlin spacing: film needs support at 1.0–1.2 m; wider spans let the sheet flap.
Fixing: clips versus a channel profile. A channel is what survives uplift.
Vent hardware: roll-up tubes and ratchets add load and holes in the cover.
Condensation: water runs down the cover; the gutter and the detail at the post decide where it goes.

Thickness is not the only number

A 200 μm film with poor UV stabilisation fails before a 150 μm film with good stabilisation. Buyers comparing on thickness alone are comparing the wrong number. Ask for the UV stabiliser percentage and the expected service life in months at your latitude.

A practical habit

Keep one roll of spare film and a box of clips on site. Most cover failures are local, and a torn sheet with a spare roll is a morning's work; without one it is a season.

Open selection list

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