When insects come in, and when they do not
Insects rarely drift in by chance during the day. They come in when the rooflight is open, the air outside is warm and still, and the room below is brighter than the sky.
In daylight a rooflight is the brightest thing in the room, so a fly that has found its way indoors tends to head up towards the glass and back out again. After dark the picture reverses. The lit room becomes the bright patch in a dark landscape, and moths, crane flies and midges are drawn towards it through any gap they can find. A rooflight left open for night cooling above a kitchen with the downlights on is about as inviting as a house gets.
Cambridge adds its own twist. The city sits low beside the Cam, with the Fens, water meadows and garden ponds all around, and still summer evenings suit midges and mosquitoes. Homes near Grantchester Meadows, the river at Chesterton or the drains out towards Ely will notice this more than a house on higher, breezier ground. Wasps are a daytime nuisance in late summer, and a kitchen rooflight above a fruit bowl or a bin will interest them.
Height helps, but less than people expect. A flat rooflight on a single-storey rear extension is only a few metres above the garden, where insects are busiest, and a loft roof window in a terrace is not much higher. When the rooflight is closed, of course, nothing gets in at all: the seals that keep out wind and rain keep out insects too.
How an insect screen fits each type of rooflight
The screen always sits on the room side of the opening sash, so the rooflight can open and close outside it without touching the mesh.
That arrangement is what makes screens practical on electric units. The motor moves the glazing up and away from the frame, while the screen stays drawn across the reveal below. You can leave the screen closed all summer and still open and shut the rooflight from a switch, a timer or an app. How each design takes a screen differs, and it is worth deciding before the reveal is lined, not after.
| Rooflight type | Usual screen | Point to plan |
|---|---|---|
| Pitched roof window | Roller screen in the lining | Shares space with a blind |
| Hinged flat rooflight | Screen within the kerb | Needs a deep enough upstand |
| Sliding rooflight | Pleated or roller screen below | Wide spans need support |
| Access hatch | Removable or pleated screen | Must clear the way out |
On a pitched roof window, screens are made to size for the frame and run in side channels in the lining, pulled down to a catch at the bottom. On a hinged opening flat rooflight the screen fits inside the upstand, which is why the depth and finish of the kerb matter when the rooflight is first specified. Sliding rooflights open a large section of roof, so the screen has to span a wide gap and is usually pleated so it folds into a slim pack. On a roof access hatch the screen must never block the route onto the roof, so it either pleats fully clear or lifts out.
When a screen is worth fitting
A screen earns its place wherever the rooflight will be open for long spells, at night, or over a room where an insect is more than a minor annoyance.
- Bedrooms and loft rooms. A loft bedroom in a Romsey or Mill Road terrace is where people most want the window open overnight, and where a mosquito is least welcome. Our answer on whether a rooflight can be left open at night covers the security and rain side.
- Kitchens. Food, sweet smells and bright task lighting draw wasps by day and moths by night.
- Night cooling. If you plan to use the rooflight for stack ventilation on summer nights, it will be open when insects are most drawn to light.
- Homes near water or open land. Riverside streets, village cottages by the Fens and new homes beside parkland and balancing ponds.
- Anyone with an allergy to stings. A screen turns an open rooflight from a worry into a non-issue.
A screen matters less on a rooflight you open for ten minutes to clear steam, or over a stairwell you pass through. There, turning the lights down before opening, or airing the room in daylight, does most of the job.
What a screen changes in the room
A screen costs you a little airflow and a little light while it is drawn, and nothing at all once it is rolled away.
Mesh fine enough to stop midges also slows the air passing through it. The effect is modest for background airing but noticeable for purge ventilation, where you want the largest possible open area to clear heat quickly. Our guide to using rooflights for ventilation explains free area and why it matters. If a rooflight is your main route for purge ventilation, we allow for the screen when we size the opening.
Light is the other trade. Mesh is a dark, fine weave, and drawn across a north-facing rooflight it takes a little of the soft, even light the room depends on. On an east or south slope, where you may already want to temper the morning or midday sun, that slight shading is hardly felt. This is the kind of detail we cover in the written light plan: where the rooflight sits, which way it faces, what glass and blind it has, and whether a screen will be drawn for most of the summer. How we plan the light sets out the approach.
Questions people also ask
Can an insect screen be added to an existing rooflight?
Often, yes. Roof windows usually take a screen made for their frame size, and flat rooflights can take one if the upstand is deep enough to hold it. Where it will not fit neatly, it can make sense to plan it into a replacement unit. Our electric and opening rooflight installation page explains how we approach both.
Will a screen stop an electric rooflight from opening?
No. The screen sits below the sash on the room side, so the rooflight opens outward above it. You can operate the rooflight with the screen drawn or rolled away.
Do opening skylights let in spiders?
Spiders tend to arrive by walking in along frames and walls rather than flying, so a screen that fits snugly in its channels helps, and a closed rooflight with sound seals keeps them out.
Is a screen the same as a blind?
No. A blind controls light and privacy; a screen stops insects while letting air through. Some units combine the two, and electric blinds for opening rooflights explains the options. To plan either, book a light survey.
