No-See-Um Screen for Pool Cages and Lanais in Florida

You sit down on the pool deck at dusk. Within a few minutes your ankles itch, and you slap at something you never saw. Your cage has no holes. So what is biting you? If you live near the Gulf, the answer may be a bug small enough to walk through ordinary screen, and the fix may be a no-see-um screen with a tighter weave.

This guide goes past the basics. It covers what no-see-ums are, what a 20x20 weave changes, what you give up in air and view, which towns along our coast deal with them most, and how to decide between new no-see-um screen on part of the cage or all of it. For the four screen types side by side, start with our pool cage screen types guide. This one stays on the bug.

What No-See-Ums Are

No-see-um is the common name for a biting midge. The University of Florida’s extension service (UF/IFAS) calls them tiny bloodsucking flies and says many species are less than one twenty-fourth of an inch long, about 1 millimeter. Adults are usually 1.0 to 2.0 millimeters, and the average among Florida species is about 1.5 millimeters (UF/IFAS, Biting Midges, No-See-Ums). That is a speck.

Three more facts from UF explain why they bother pool and lanai owners:

• They live where the water is. UF says several species are coastal pests that use the marshes, swamps and mangroves of coastal Florida as larval habitat. Those species can reach very high numbers and, in UF’s words, “drive even the most stout-hearted nature lovers indoors.”
• They bite at the hours you are outside. An older UF publication on coastal biting midges says the greatest biting activity is around dawn and dusk. It adds that some biting may continue through the night, but rarely during the day unless the sky is heavily overcast and the winds are calm (UF/IFAS, Biting Midges of Coastal Florida). That is your evening on the deck.
• Only the females bite. The same publication says so. They take blood to make eggs, and the feeding takes a few minutes, which is long enough for a welt.

That size is why you never see them. The older UF publication opens with the same experience: coastal residents and visitors know something is biting, but when they look for the offender, none can be found.

Why Your Screen May Not Stop Them

UF’s publication on biting midges makes a plain point about screens: regular window screens do not exclude biting midges, because the openings are too large. The openings of no-see-um screen are small enough to keep them out, UF says, though that screen is not typically used on windows and doors.

That is the reason for the product. Here is how the two pool cage weaves compare, using Phifer, the screen maker we use on rescreens.

18x14 pool and patio screen. The numbers are strands per inch in each direction. Phifer’s own FAQ explains mesh size as counting openings per inch: “If you counted 18 horizontally, and 16 vertically, your mesh size is 18x16.” So 18x14 means 18 across and 14 up. Phifer says this fiberglass screen is a traditional choice for patio and pool enclosures, designed where extra strength is wanted, and that it keeps out most tiny insects (Phifer, pool and patio screening; Phifer catalog sheet).

20x20 no-see-um screen. Phifer describes it as a tightly woven fiberglass mesh designed to control small insects, and says it protects against no-see-ums, gnats and sand flies (Phifer, No-See-Um screen). On its FAQ, Phifer says the 20x20 no-see-um screen provides the maximum protection among its fiberglass options (Phifer FAQ).

Do the arithmetic and the difference is easy to see. An 18x14 weave has 252 openings in a square inch (18 times 14). A 20x20 weave has 400 (20 times 20). That is many more openings, each one smaller. Smaller openings are what keep out an insect that is a millimeter or two long.

Now the honest part. Phifer says 18x14 keeps out “most” tiny insects. No source we read says that standard pool screen lets no-see-ums through every time. What the sources support is narrower: no-see-ums are among the smallest biting insects, regular window screen does not stop them, and the 20x20 weave is the one made to. If you are getting bitten inside a cage with tight, whole, 18x14 screen, the weave is the likely thing to change. It is a reasonable conclusion, not a promise that you will never see another bite.

Is It the Bugs or the Screen?

Before you spend money on a different weave, check the cheaper possibilities. A screen that lets in no-see-ums and a screen that has failed look the same from your chair. They are not the same problem.

Look for tears and gaps first. A torn panel, a loose edge where the spline has pulled out, or a door that does not close tight lets in anything, mosquitoes and leaves included. A different weave does not fix a hole. A walk around the cage, panel by panel, does not take long. Our screen types guide lists the signs of worn-out screen: fading, sagging, tears and bugs inside.

Think about when and where you get bitten. Bites that come at dawn and dusk, near the water, from something you cannot find, point to midges. If you see mosquitoes on the walls, or get bitten at all hours, check the cage for openings first.

Notice what the weather is doing. UF’s older publication says biting midges rarely bite in daytime unless it is heavily overcast and the winds are calm. A still, damp evening is when they come. That is also when people sit out.

If the cage is tight, the bites fit the pattern and you live near the coast, no-see-um screen is a fair thing to price. If the cage is worn, you are rescreening anyway, and the choice of weave comes along with it.

What a Tighter Weave Costs You in Air and View

Here is what the sources say, and what they do not.

Phifer says its 20x20 no-see-um screen “still allows good ventilation and visibility” while giving some daytime privacy (Phifer catalog sheet). Its product page says the screen strikes a balance between ventilation and visibility (Phifer, No-See-Um screen).

What Phifer does not give us is a percent of airflow lost, or a percent of view lost, for 20x20 against 18x14. We looked. Retail sites and blogs quote numbers, but none of them is a Phifer number, so we are not printing any. If someone tells you a tighter weave cuts the breeze by a precise amount, ask where the number came from.

What you can say honestly:

• The openings are smaller, so a little less air passes through each square foot of screen than with 18x14. Phifer’s claim is that the ventilation is still good.
• Looking through the screen, the weave is a little more noticeable. Phifer also notes some daytime privacy, which some people like on walls facing a neighbor.
• Pool cage walls and roof are big spans of screen, so the choice affects a lot of open area at once. That is one reason to consider the tighter weave only on the walls where you sit.
• How it looks against your own pool and trees is hard to judge from a page. Ask Chris at the estimate what it looks like on a cage like yours.

UF also suggests another way to move air on a screened porch: its older publication recommends increasing air movement with high-velocity fans. It is UF’s advice for screened porches, and it costs far less than a rescreen.

Where Homes Get It Worst Along Our Coast

UF’s pattern is simple: these midges are strongest near coastal marsh, swamp and mangrove, and the species that bother people most are coastal. So the places to ask about no-see-um screen are the ones near the Gulf and its tidal water. A few from our service area, using what we know of each town:

• Hernando Beach. A grid of waterfront homes along dredged canals that run out to the open Gulf near Pine Island and Bayport. Canals and open water are close to every lot.
• Hudson. Canal-front homes around Hudson Beach and Leisure Beach, low and flat, close to the water.
• Homosassa. Homes along the Homosassa and Halls rivers, where the air stays humid year round.
• Aripeka. A small fishing village in the salt marsh on the Gulf, at Hammock Creek, where Hernando and Pasco counties meet. Salt marsh is the kind of ground UF names as larval habitat.
• Weeki Wachee. The Weeki Wachee River and the canals tucked back along it.

We are not saying every house in those towns has a no-see-um problem, or that a house in Spring Hill never will. UF says the species vary and the numbers vary. What we are saying is that if you live near that kind of water and you are bitten at dusk, you are the person this screen was made for. UF also says other species breed in treeholes and in low inland grasslands, so inland cages can still get them. The pattern of bites matters more than the zip code.

No-See-Um Screen on Some Walls or All of Them

Once you decide to try it, the next question is how much of the cage. This is where a rescreen gives you a choice.

Every rescreen we do is a full rescreen: every wall and roof panel in one job, with new spline and worn hardware like screws and door closers replaced. We do not swap a single panel. That matters here, because the screen is chosen as part of the full job, and different walls can get different screen. Rain Storm offers all the types, including no-see-um, pet and privacy.

So you have three real options:

1. All no-see-um. Every wall and the roof get 20x20. This is the choice when bites are bad everywhere you sit, or you do not want to think about where the line falls.
2. No-see-um on the walls where you sit. The side near the lounge chairs, the table or the door gets 20x20. The rest stays standard.
3. No-see-um everywhere except where something else is needed. For example, pet screen on the lower panels a dog reaches, or privacy screen on lower panels that face a neighbor. Our screen types guide covers where those go.

Two things to settle at the estimate. First, ask what each option changes in the price. Pricing is done in person because every cage is different, so we do not quote it here. Second, ask Chris how 20x20 and 18x14 compare on a cage like yours, since he will be standing in front of it.

A note on lanais and screened patios. The same logic applies: the walls closest to where you sit are the obvious ones to consider. Our lanai rescreening page covers that job, and our guide to lanai, pool cage and screen room explains how they differ.

What Else Helps, Besides the Screen

A screen is one tool. UF’s publications list others, and none of them is a cure on its own.

• Avoid peak times. UF’s first recommendation is to avoid outdoor activity during peak biting times, which means dawn and dusk.
• Use a repellent labeled for biting midges. UF says to apply repellents labeled for biting midges according to the label. It points to its repellent fact sheet for details, and notes that DEET-based repellents are the main ones people use for midges.
• Move the air. Run a high-velocity fan on the lanai or deck.
• Know that spraying has limits. UF says insecticide sprays against adult midges are mediocre at best and temporary, because new ones keep emerging. It says barrier sprays on screens can give a temporary reduction in small backyard settings, applied according to the label. UF also says Florida’s mosquito control districts are not funded to control biting midges, so there is no truck coming to spray for them.

Put together, a good plan for a coastal cage looks like this: tight, whole screen, a fan or two, and repellent on the evenings you will be out at dusk.

One more thing worth knowing: a no-see-um screen cannot help while there is a hole in the cage. If you are going to put in the money for a finer weave, it should go onto a cage that is closed up properly, which is one reason it is chosen with a full rescreen. Our post on pool cage care between rescreens covers what to watch for in the years between.

How Your Estimate Will Go

Choosing a screen is easier standing in your own pool area than reading about it. We set up a visit. Chris measures the cage, looks at the screen, the frame and the hardware, and sketches what he sees. You pick the screen: standard, no-see-um, pet or privacy, wall by wall if you like. The estimate is free and in person, and it is good for 30 days. There is no rush to decide on the spot, and checking with your HOA first is fine. We help with HOA paperwork when it is needed.

If you have been bitten on your own deck and want to know whether no-see-um screen fits your cage, ask for a free estimate or call (727) 857-3714. You can also read the full job on our pool cage rescreening page. Rain Storm Solutions is a Florida Certified Specialty Contractor, license SCC131154760, and rescreens come with a 1 year warranty.