A vent opening covered with insect net is a compromise. The finer the mesh, the more insects it stops and the less air it passes, and a house that cannot vent properly runs hotter and wetter than it needs to. This net is a 40 mesh construction in virgin HDPE, the count we supply most often for greenhouse vents, side openings and net house walls where the crop still has to be cooled. The yarn carries a UV stabiliser and we quote a five year working life on that basis. It comes as a roll up to 5 m wide, in 30, 50 or 100 m lengths, white or transparent.
Netting over a vent is doing two jobs at once, and they pull against each other: it has to keep the pest out, and it has to let the air through. Every count you choose on a greenhouse trade one against the other, and this one is a middle count in virgin HDPE for exactly that reason.
The count is the whole decision. Move to a finer mesh and it stops smaller insects, but it also puts more yarn in the way of the air, and a house that cannot dump its heat in the afternoon runs hotter and wetter than the crop wants. Move coarser and the air is easy but the insects are back. A 40 mesh is the count growers settle on for vents, side openings and doorway screens, where insect control matters but the structure still has to breathe. If thrips or whitefly are your problem rather than the larger pests, tell us and we will quote a finer construction instead of leaving you to guess.
The roll is cut to cover roof vents, side curtains and doorways on a greenhouse, and it is also used to close in the walls of a net house where the structure is open rather than glazed. It is white or transparent as standard, which keeps the light cost low when the net sits over growing plants. Growers running trays under the same cover often order a planting bag with the netting, and the wider shade net range covers the grades where light rather than insects is the problem to solve.
| Material | Virgin HDPE with UV stabilised yarn |
| Mesh | 40 x 25 and 50 x 25 |
| Weight | 80 to 130 gsm |
| Width | Up to 5 m |
| Roll length | 30 m, 50 m and 100 m, or made to request |
| Colour | White or transparent |
| Working life | 5 years |
| MOQ | 5000 m2 |
A vent screen works only if it is held tight. Loose netting flaps in the wind, chafes against the frame and opens along the fixings, so the cloth is usually run into an aluminium profile, trapped under a batten or held on wire lock channel, with the load spread along the full edge rather than carried by a few points. Because the roll runs up to 5 m wide, most vents and net house bays are covered in a single drop with no seam down the middle to fail. Where the requirement is a shade rate rather than insect control, a knitted monofilament net is the better fit.
Mesh count, width, roll length and colour are made to order, and the standard minimum order quantity is 5000 m2. Each roll is packed in one strong polybag with a label, and we run 30 m, 50 m and 100 m lengths as the usual options. The first thing to confirm on an enquiry is the vent or bay dimensions and how the net will be anchored. Buyers tracking what is going into protected cropping can follow trade coverage such as HortiDaily and FreshPlaza for what growers are installing.
Will a 40 mesh net reduce the ventilation in my house?
Any insect net reduces airflow across the opening, and a finer mesh reduces it more. 40 mesh is the count we supply most for vents and side curtains because it holds the insects out while still letting the house vent. Tell us the vent area and the crop and we will advise.
Can you supply a finer mesh for thrips or whitefly?
Yes. The range runs from 20 to 60 mesh and we make to order. The finer the count, the more air you give up for it, so it is worth sizing the vent on the finer mesh rather than changing the count alone.
How is the net fixed so it does not flap?
It is run into an aluminium profile, trapped under a batten or held on wire lock channel so the load is spread along the edge. Tell us the frame and we will confirm the width and the drop you need.
Tell us the vent or bay dimensions, the mesh count you have in mind and the roll length you buy in, and we will confirm the width, the roll sizes and the packing that suit your order.
Mark Wu, Co-founder & Technical Director, Sichuan Zhifang Net Industry. 15 years manufacturing agricultural nettings for growers in 32 countries.
