Shading and Cleaning Glasshouse Roofs by Drone: Two Jobs, Two Seasons
Updated: Sep 13
Glasshouse roof work tends to get talked about as one job — "get the roof done" — when it's really two jobs at opposite ends of the season, and mixing up the timing costs a grower either light or heat, depending on which way they get it wrong.
Spring: put
ting shading on
Shading compounds go on in April to June, while conditions are warm, dry and calm enough for the coating to bond properly to the glass or polycarbonate. Applied at that point in the season, a shading layer reduces the average internal temperature by as much as 5°C during peak sun — which is the difference between a crop that copes with a hot June and one that shows heat stress, flower drop or scorch on the worst days.
That's the whole point of doing it before the heat arrives rather than during it: a coating applied in a heatwave is a coating going on too late to help with that heatwave.
Autumn: taking it back off, and cleaning at the same time
By September and October, the same coating that was protecting the crop from too much light in June is now blocking light the crop needs as day length drops. Removal restores light transmission, and it's the natural point to clean the glass itself rather than schedule a separate visit — algae, dirt and general fouling on glass reduce light transmission by up to 10% on their own, on top of whatever the old shading residue is still blocking.
That matters more than it sounds. UK horticultural guidance treats roughly every extra 1% of light reaching the crop as worth about 1% more production, and that relationship is most valuable exactly when natural light is already falling away for the winter. An autumn clean isn't cosmetic — it's recovering production capacity at the time of year growers can least afford to lose it.
Why glass changes the job
A polytunnel roof is one continuous sheet. A glasshouse roof is hundreds of individual panes, glazing bars, gutters and ridge lines — more edges for dirt and old coating residue to collect on, and a surface where a person walking across it is a genuinely different risk than on polythene. A cracked or slipped pane isn't a minor inconvenience; it's a repair bill and a gap in the structure. Working the roof from the air removes foot traffic from the equation entirely, on the structure where that matters most.
Booking it as one arrangement rather than two calls
Because shading and removal-and-clean are opposite-season jobs on the same structure, the two visits make more sense as a single annual arrangement — application booked for spring, removal and cleaning booked for autumn — than as two separate one-off enquiries months apart. It also means the site only needs describing once. We cover the polytunnel side of this on our horticulture page, alongside a real polytunnel shading job we've completed.
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