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Short answer: an aperture of about 1.0–1.4 mm keeps out house flies, wasps and most mosquitoes while letting air and light through. For tiny biting midges, go down to about 0.6 mm or less and accept less airflow. Use V2A stainless steel for normal sites and V4A on the coast.
Which aperture keeps which insects out?
The aperture is the clear opening between two wires. It decides what gets through:
| Aperture | Keeps out | Airflow |
|---|---|---|
| 1.2–1.4 mm | flies, wasps, moths, most mosquitoes | high |
| about 1.0 mm | also smaller mosquitoes and gnats | good |
| 0.5–0.6 mm | also biting midges | reduced |
Smaller openings always cost airflow and visibility. Start with the largest opening that stops the insects you actually have.
Why does the wire thickness matter?
A thinner wire leaves more open area, so more air and light pass through and the screen is harder to see. A thicker wire makes the mesh stiffer and more robust against pets, hail and cleaning. The open area in the table below is calculated from aperture and wire diameter, so you can compare meshes directly.
| Mesh | Aperture | Wire | Open area | Weight | Price |
|---|---|---|---|---|---|
| V2A 1.4 × 0.25 mm | 1.4 mm | 0.25 mm | 72 % | 0.6 kg/m² | 25 €/m² |
| V2A 1.25 × 0.4 mm | 1.25 mm | 0.4 mm | 57 % | 1.23 kg/m² | 36 €/m² |
| V4A 1.25 × 0.4 mm | 1.25 mm | 0.4 mm | 57 % | 1.23 kg/m² | 40 €/m² |
| V2A 1 × 0.3 mm | 1 mm | 0.3 mm | 59 % | 0.88 kg/m² | 32 €/m² |
| V2A 0.6 × 0.25 mm | 0.6 mm (600 µm) | 0.25 mm | 50 % | 1 kg/m² | 36 €/m² |
| V2A 0.5 × 0.2 mm | 0.5 mm (500 µm) | 0.2 mm | 51 % | 0.73 kg/m² | 32 €/m² |
Stainless steel or fibreglass?
Stainless steel lasts longer and stays taut. It does not sag, does not become brittle in sunlight and resists cat claws far better than fibreglass or plastic screens. The trade-off is that it is stiffer and heavier, so it needs a rigid frame. Choose V4A within reach of sea air; elsewhere V2A is sufficient. See V2A vs V4A for the details.
How do you fit a stainless steel insect screen?
Fit it in a rigid frame, under light, even tension:
- Measure the clear frame opening and add the overlap your frame profile needs.
- Order the sheet cut to that size; we cut every sheet to your width and length.
- Clamp or bead the mesh along one long side first, then tension towards the opposite side.
- Fold or cover the cut edges. Cut wire ends are sharp, so wear gloves.
For vents and air bricks, fix the mesh over the opening with stainless screws and washers so that no gap remains at the edge.
What insect screen mesh is not suited for
- Roll-up and pleated screens. These need a flexible fabric; stainless mesh would kink.
- Pollen protection. Pollen grains are far smaller than any insect screen opening and need a dedicated pollen fabric.
- Frameless fixing with tape or Velcro. The mesh is too stiff and heavy for adhesive fixing.