Insect Proof Net FCW-30 is the net in the photograph above: a fine HDPE mesh stretched over the arched frame of a tunnel, closing the openings a crop would otherwise be exposed through. It is quoted by mesh and by wire diameter rather than by a single "fine" or "coarse" description, because those two figures are what decide the opening in the cloth.

Two numbers describe the cloth and they should always be read together. The first is the mesh: 30 openings per inch. That sets the pitch of the weave - 25.4 mm divided by 30 gives a pitch of about 0.85 mm. The second is the wire diameter, 0.14 to 0.15 mm, which is the thickness of the HDPE thread itself, and that comes off the pitch to leave the clear opening the insects meet. Worked out on the figures above, the opening is about 0.70 mm, and a thicker wire at the same mesh would give a smaller opening with a heavier cloth.

This is why the pair matters more than a name. When you enquire, tell us the mesh the crop needs and the wire you want to hold that mesh under tension, and the net is quoted on those two figures. If you are working to a stated opening for the insects you are dealing with, give us that figure instead and the mesh and wire are matched to it.

The net is made in three standard widths - 1 m, 1.5 m and 2 m - and it is sewed to any width that a house needs, so a wide span is covered by a sewn sheet rather than by overlapping loose strips. Standard length is 450 m on a roll, and each roll is packed in one woven bag. A sewn sheet keeps the opening size uniform across the whole cover, which is the point of sewing rather than lapping.

Before ordering, measure the surface that will actually be netted rather than the floor area: the arched cover, the side walls, the gable ends and the openings, plus the allowance the frame radius takes up when the net is pulled over it. Give us the finished width and the total length, and it is worked out from the 450 m roll, with the number of rolls and the sewn width confirmed with the order. Sewed panels are supplied to that measurement, so nothing has to be cut on site.

The net carries a use time of 5 years under normal usage, and normal usage is mostly a question of how it is fixed. It is stretched over the frame - the hoops, the ridge and the bottom rail - and held under even tension, so that it does not flap and work against the tube at every gust. A net that is slack will rub itself and the frame, and abrasion is what shortens the life of a mesh long before the material is at fault.

Two more points are worth settling before the net goes on. Sharp edges, cut tube ends, bolts and wire ties are cleaned up or taped before the net touches them, because a fine mesh catches on anything proud of the frame. And the net is kept clear of the crop canopy and of stacked material, so that nothing presses against the cloth and holds a wet patch in it. The frame it is stretched over can be seen in the galvanized frame tube range, and small crops are held off the mesh with plant clips.

The net is a screen for openings, so the first job is to list them. Roof vents and side vents are the obvious ones, and they are the openings that stay open the longest through the season. Side walls and the gable ends matter where they are the only barrier between the crop and the outside. Doors and tunnel ends need it for the same reason, because an unprotected doorway is an opening the whole length of the house. Finally, wherever cooling fans and wet curtain are fitted, the fan aperture and the curtain face are openings too, and a house is only as closed as its least protected opening.

Model	Insect Proof Net FCW-30
Material	HDPE with Anti-UV Protect Addition
Standard width	1 m, 1.5 m, 2 m; sewed to any width is available
Standard length	450 m
Mesh per inch	30
Wire diameter	0.14-0.15 mm
Packing	One roll with one woven bag
Use time	5 years under normal usage

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The net is quoted from the roll, so a house is priced on the sewn width and the total length it needs. Send the mesh and wire you want, the finished width and the length, and rolls, sewing and packing are confirmed together. It sits in the same order as the rest of the planting tools and accessories and the greenhouse equipment range.

Reference material on integrated pest management in protected cultivation is published by the FAO, and commercial greenhouse practice is reported by Greenhouse Grower.

Q: What do the 30 mesh and the 0.14-0.15 mm wire add up to?
A: A pitch of about 0.85 mm and a clear opening of about 0.70 mm. The mesh sets the pitch - 25.4 mm divided by 30 - and the wire diameter comes off it, so at the same mesh a thicker wire gives a smaller opening and a heavier cloth. If you are working to a stated opening rather than to a mesh count, give us that figure and the two are matched to it.

Q: What widths and lengths are standard, and can a wider sheet be had?
A: Standard widths are 1 m, 1.5 m and 2 m, and the net is sewed to any width, so a wide span is covered by one sewn sheet instead of overlapping strips. Standard length is 450 m on a roll, packed one roll to a woven bag.

Q: How should the net be fixed so it reaches its full working life?
A: Stretched over the hoops, the ridge and the bottom rail under even tension, so that it cannot flap and rub. The use time of 5 years is quoted under normal usage, and abrasion - a slack net working against the frame - is what ends a mesh early. Sharp tube ends, bolts and wire ties are taped before the net goes on.

Q: How far does one 450 m roll go?
A: It depends on the sewn width, so the roll is planned from the surface to be netted rather than from the floor area. Measure the arched cover, the side walls, the gable ends and the openings, add the allowance the frame radius takes up, and give us the finished width with the total length; the number of rolls is then confirmed with the order.

Q: What is the net made from, and how is it packed?
A: HDPE with Anti-UV Protect Addition, so that the cloth holds its opening outdoors through the season. It is supplied as Insect Proof Net FCW-30, one roll with one woven bag.

Q: Which openings on a greenhouse should be netted?
A: Roof and side vents first, because they stay open longest. Then the side walls and gable ends where they are the only barrier, and the doors and tunnel ends, since an open doorway is an opening the whole length of the house. Fan apertures and the face of a wet curtain are openings as well, and a house is only as closed as its least protected opening.

If you need to ask a question and get some help to find the best greenhouse for you, then just call us on +86 191 5068 3942 or send E-mail to sales@cngreenhouses.com