Do electric rooflights come with insect screens? Some ranges offer a fly screen

Warm air rises and leaves by the highest opening. That is the reason an opening rooflight ventilates so well, and the same reason insects find it.

A rooflight set in a pitched or flat roof is often the highest opening in the house. On a still summer evening, the light from the room below and the warmth rising through the gap draw flying insects towards it. In Crawley and the wooded country to the south, around the Weald and the Downs, that means moths, gnats, flies and the odd wasp wandering in through a gap you opened to cool the room.

For a kitchen, the concern is food and cooking smells. For a bedroom, it is a whine at the ear at two in the morning. Either way, the same thing happens: people shut the rooflight, and then the room runs warm. A screen lets the rooflight do the job it was bought for.

There is a knock-on effect for noise. A room you can leave open at night, because the screen keeps the bugs out, is also a room that hears the night. Near the Gatwick approach paths or beside the A23, the question of how wide and for how long to open the unit gets a second answer. Our page on night ventilation without the noise deals with that side.

Screens for overhead glazing are not the same as the flyscreen on a garden door. They hang, slide or roll, depending on the rooflight.

• Roll-up screen. A mesh on a roller in a slim cassette, pulled across the opening on side guides and retracted when not needed. It stores out of sight, which suits a room where the rooflight is also meant to be a clean feature.
• Pleated screen. A folded mesh that concertinas along a track and gathers to one side. It copes well with longer openings.
• Fixed frame screen. A mesh panel in a light frame that clips or slots into place over the opening. It is the simplest, and because it does not move it has little to go wrong.

Any of these can sit inside the room, on the underside of the rooflight, or be integrated into the frame by the maker. The integrated version looks best and fits best, but it is only available on ranges that design for it. A screen bought separately has to match the depth and the opening.

For a hinged rooflight, the screen has to sit below the sash and stay clear of its swing. For a sliding rooflight, it has to work with the track and the stack, the point where the moving glass parks. Our page on hinged or sliding rooflights helps you picture where the space is.

A fine mesh stops insects, and it also slows air and dims light a little. Both effects are small, and both are worth knowing.

Air first. Mesh is an obstacle, however thin. A rooflight with a screen moves slightly less air than the same rooflight without one. On a warm night you will not notice it, but if you are relying on a rooflight to help a room purge heat, the screen is one more reason to size the opening with a little to spare. Our answer on cooling a house with an opening rooflight explains how the airflow works.

Light second. A screen takes a little of the daylight that comes through the glass. Darker mesh takes a little more, and a finer weave takes a little more again. For a rooflight whose whole purpose is daylight, choose a light mesh, and keep the screen retracted when the unit is shut.

Then there is the sound of the thing. A loose mesh can flutter in a draught, and a hard frame can tap against the sash in wind. That is an installation detail, and it belongs on the list of things to check. A screen that hums or ticks at night defeats the point of a quiet room.

Under an electric opening rooflight there is only so much space, and the motor, the blind and the screen all want it.

The actuator takes one corner. A blind takes the underside of the glass. A screen wants to sit close to the opening, which is also where the blind wants to roll. Sort these out on paper and everything fits. Leave them to chance and one of the three ends up working badly.

If you want both a blind and a screen, ask the maker whether they are designed to work together. Some systems share side guides, which saves depth and looks tidy. Others do not, and then the order of layers matters: screen nearest the glass, blind below it, is a common arrangement, but it depends on the range. Our answer on fitting a blind to an electric rooflight covers that half of the planning.

Then look at the control. A screen on a motor can share the same remote or panel as the sash. A manual one is pulled by hand, and at ceiling height that can be awkward. Our page on controls for electric rooflights shows how each is set up.

A screen is one line on the quote that saves a summer of frustration.

When you say a screen matters, we record the type, the mesh, where it sits and how it clears the sash, in the written note that comes with every quote. It is the same note described on the quiet spec page, and it lets you compare two quotes on like terms. If a range does not offer a screen, we will say so at the survey rather than fit something that does not belong. For a kitchen extension, the wider picture is in electric rooflights over a kitchen extension. To have a screen specified for your room, get a quote.

The same few come up every summer.

Can a screen be added to a rooflight I already have?

Sometimes. It depends on whether the maker offers one for that model, and how much clear depth there is under the sash. Measure it with the glass fully open. A fixed frame screen is the most likely to work as an afterthought.

Does a screen spoil the light?

Slightly. A light, fine mesh keeps the effect small, and a roll-up screen can be retracted when the rooflight is closed, so it costs nothing when you do not need it.

Will a screen keep out leaves and pollen?

It keeps out leaves and larger debris. Very fine pollen can pass through a standard mesh, so do not treat a screen as a filter. The page on ventilating a room with an opening rooflight explains what a screen can and cannot do for air quality.

Does a screen matter if the rooflight only opens a little?

Often yes, because a small gap at the top of a room still draws insects towards the light. Whether you need one depends on how long the rooflight stays open, and on which room it serves. The hub page on electric and opening rooflight installation lists the options side by side.