There is a point every evening when the air outside finally turns pleasant, and the sensible thing to do is open the windows. The problem is that everything else outside notices at the same time. Mosquitoes, flies, moths and whatever else is drawn to a lit room all arrive together, and within ten minutes the windows are shut again and the air conditioning is back on.

Most households accept that trade-off as permanent. It is not. The reason insects get inside has less to do with open windows than people assume, and the fix is usually cheaper and less intrusive than expected.

Why sealing the house is the wrong answer

Keeping windows closed year-round solves the insect problem by creating three others. Indoor air gets stale, because nothing is diluting the cooking smells, cleaning products and general staleness that build up in a sealed room. Humidity climbs, particularly in kitchens and bathrooms, and that eventually shows up as condensation on cold surfaces and mould in the corners nobody looks at. And the cooling bill goes up, because the only thing moving air is now a machine.

Natural ventilation does real work. Even an hour of cross-breeze in the evening drops indoor humidity, clears accumulated odours and brings the temperature down enough to let the air conditioning cycle off. Giving that up to avoid mosquitoes is solving a small problem by creating a larger one.

Where insects actually get in

Here is the part that surprises people. If your windows have been shut all week and you are still finding mosquitoes in the bedroom, they did not come through the window.

The usual routes are much less obvious:

Gaps around the window frame itself, where the frame meets the wall. Sealant shrinks and cracks over time, and a gap of two or three millimetres is a comfortable doorway for most flying insects.

The track of a sliding door. Sliding patio and balcony doors almost never seal at the bottom corner of the track, and that corner is at ground level where crawling insects travel.

Under the front door. A worn threshold seal leaves a gap you can see daylight through.

Bathroom and kitchen extract vents. These vent to the outside and many have no insect grille at all, just a flap that stays open.

Air conditioning pipe penetrations. Where the refrigerant pipes pass through the wall there is usually a drilled hole, and the putty that was meant to seal it has often dried out and fallen away.

Drains and overflow pipes, particularly floor drains in bathrooms and utility areas that are rarely used and so have no water left in the trap.

It is worth walking the perimeter of the house once with a torch, at night, looking from the inside out. Anywhere light escapes, an insect can enter. Dealing with those gaps often reduces the problem more than anything you do to the windows.

Mesh types compared

Once the gaps are closed, the windows themselves can be screened. The mesh matters more than most people realise, and there are real differences.

Fibreglass mesh is the standard choice and the most common for good reason. It is coated, flexible, does not dent, and springs back if something leans into it. It is woven to roughly eighteen by sixteen strands per inch, which stops mosquitoes and flies while staying close to invisible from a few feet away.

Polyester mesh is stronger and more tear-resistant than fibreglass, which makes it a better choice for doors and for ground-floor windows that get handled a lot. The strands are slightly thicker, so visibility through it is a little lower.

Aluminium mesh is rigid and long-lasting, and holds its shape in large spans without sagging. The trade-off is that it dents permanently if knocked, and in coastal or high-humidity areas it can corrode at the edges where the coating is cut.

Fine mesh, sometimes sold as no-see-um mesh, has a much tighter weave for very small insects like sandflies and midges. It works, but a tighter weave means less open area, so airflow through the window drops noticeably. Only choose it if you actually have a problem with insects small enough to pass through standard mesh.

Pet-resistant mesh uses heavier strands and is worth considering on doors at animal height.

For most homes, standard fibreglass on windows and polyester on doors is the right combination.

Fitted screens and temporary fixes

There are two broad approaches, and they are not equivalent.

The temporary route is adhesive mesh kits, velcro strips and hanging magnetic curtains. They are inexpensive and work for a season. The weakness is always the fixing rather than the mesh. Adhesive tape loses grip in heat, velcro collects dust and stops closing properly, and sun exposure makes both brittle within a year. They also look like what they are, which matters if you intend to live with them.

The permanent route is a framed screen made to the size of the opening. Here the choice is about how the screen behaves when you do not want it: fixed panels stay in place permanently and are the simplest and cheapest; hinged screens swing open like a second window; pleated and retractable screens fold or roll away into a slim side cassette and effectively disappear when not in use; and magnetic screens sit on a light frame that lifts off entirely for cleaning.

In hotter regions where windows stay open for much of the year, made-to-measure framed screens are the normal approach rather than a luxury, and specialists such as Dubai Fly Screens will measure the opening and fit the frame without drilling into existing joinery.

For most homes a mix works best: retractable screens on the windows that get opened daily, fixed panels on the ones that rarely move, and a hinged or pleated screen on the balcony door.

What to check before you buy

Measure the opening, not the glass. Screens fit the frame, and the difference is often several centimetres.

Ask what the mesh actually is. “Insect mesh” is not a specification. Ask for the material and the weave.

Ask about the frame finish. Powder-coated aluminium holds up in sun; bare or painted finishes chalk and fade.

Ask whether fitting requires drilling. If you rent, or if your windows are aluminium or uPVC that you do not want holes in, tape-fixed or tension-fitted frames exist and work.

Ask whether the mesh can be replaced separately. Mesh is the part that eventually fails. If replacing it means replacing the whole screen, that is a design flaw, not a feature.

Ask what the warranty covers. A frame warranty and a mesh warranty are usually different lengths, and the mesh one is the one that matters.

Getting this right means the windows stay open in the evening, the air conditioning runs less, and nothing comes in that you did not invite. That is a reasonable return on a fairly small job.