Greenhouse shade-netting guide

Decide whether the greenhouse needs netting

The aim is not to keep a greenhouse dark all summer. Netting is useful when a measured temperature peak or leaf scorch persists despite working ventilation. A sunny roof panel and the side facing the strongest afternoon sun may need different treatment. The RHS ventilation and shading guidance recommends shading as a supplement to adequate air exchange, not a substitute for it.

Use a shaded max/min thermometer at plant height for a baseline. Note which plants suffer first, the time of day and whether door and roof vents were open. If a crop is healthy and temperatures are manageable, extra mesh may simply take away useful light. The broader overheating action guide sets out the order of fixes.

Understand percentage and placement

A product labelled “30% shade” does not promise that the greenhouse will be 30% cooler. Mesh specifications generally concern light exclusion; actual temperature depends on outside weather, air movement, glazing, roof height and how much area you cover. Avoid selecting by percentage alone. Measure the section to cover, allow for the fixing method and consider a trial on one elevation before wrapping the whole structure.

External mesh can intercept sunlight before it crosses the glazing. Internal netting is often easier to reach and remove but lets more solar energy into the enclosure before it is shaded. Neither should hang against a hot plant canopy or touch moving vent parts. If the greenhouse maker prohibits attaching items to glazing bars, use an approved freestanding or adjacent support rather than improvised fixings.

Fit for wind, access and airflow

Lay out the mesh so it can be tensioned without distorting the frame. Check eyelet spacing, suitable clips or cords and an accessible way to release the cover. Do not drill a greenhouse frame or tie netting to a delicate vent arm unless the manufacturer permits it. Leave the door and roof vents their entire travel. A netted roof can catch wind; check it after gusty weather and remove it if the fixings cannot remain secure.

Do not work from unsupported glass or polycarbonate, and do not lean on roof panels. If the roof cannot be safely reached, a ground-level fitting plan or professional installer may be the better choice. Keep the path to emergency access and the door clear of trailing ties.

Make the trial easy to review

+Record which elevation is covered, how much mesh is fitted, the vent positions and the maximum at crop height. Compare broadly similar sunny days rather than a hot day before fitting with an overcast day afterwards. Keep an eye on the plants behind the most shaded section: a cooler thermometer is not a success if the crop loses too much light.

If heat remains excessive, recheck the air path and whether an automatic vent actually opens fully. If the crop becomes weak or slow during dull weather, reduce coverage before adding more equipment. A removable arrangement gives you a useful seasonal adjustment; a permanently wrapped greenhouse makes it harder to respond to changing conditions.

Reassess through the season

After fitting, reset the thermometer and compare conditions on similar sunny days. Observe flowering and growth as well as heat relief. More shade is not automatically better: plants may become soft or slow under excessive cover, especially during dull UK spells. Roll the netting back when conditions change, clean it before storing, and inspect the greenhouse ventilation route. If you are also using fans, remember that a circulation fan cannot make up for blocked fresh-air openings.