Can mosquitoes get through window screens? Only through a hole, a tear, or a gap.
Total Screen repairs, rescreens, and replaces window screens across San Diego.
In this guide we explain: where a window screen fails, what the numbers on screen mesh mean, & what a no-see-um screen adds.
A window screen stops mosquitoes only while the mesh is intact, which is why the Centers for Disease Control and Prevention says to “repair holes in screens,” so get mosquito screens installed today.[1]
Can Mosquitoes Get Through Window Screens?
An intact window screen keeps mosquitoes out of a home, and the CDC says to use screens on windows and doors.[1]
A mosquito does not chew, cut, or force its way through screen mesh, and it does not fit through the square openings in the weave.
A mosquito flies in through a rip, a tear, a hole, or a gap where the frame no longer seals.
Landing on a window screen is not the same as getting past one.
The answer to can mosquitoes get through window screens depends on the condition of the window screen, not on the weave.
The CDC's instruction is to repair holes in screens to keep mosquitoes outdoors.[1]
Where A Window Screen Fails
Torn mesh is the most obvious failure, and the one the CDC names.[1]
A tear does not have to be large to matter.
A window screen frame that sags away from the window leaves a gap along the edge.
A tear is the only one of the four failures that is a hole in the mesh.
A gap at the frame lets mosquitoes in as reliably as a hole in the mesh.
“Spline” is the rubber cord that holds the mesh into the frame, and loose spline lets the mesh pull away at a corner.
A screen door that no longer closes flush leaves a gap down the latch side.
How To Check A Window Screen In Two Minutes
Checking a window screen takes about two minutes, and needs nothing but a light.
Hold a light on one side and look from the other, because a hole shows up as a bright pinpoint.
Run a finger along each edge of the frame and feel for a gap.
Press gently on the middle of the mesh and see whether the mesh has gone slack.
Check each corner, where loose spline lets the mesh lift first.
A window screen that passes all four checks is still doing its job.
For the months a window screen has to hold, read our guide: When Do Mosquitoes Come Out In San Diego.
What The Numbers On Screen Mesh Mean
Screen mesh is measured in threads per inch: a standard 18×16 mesh carries eighteen threads one way and sixteen the other.[2]
Standard mesh is what most San Diego homes already have, and standard mesh stops mosquitoes.
Strands or threads, the number on a mesh label is how many cross one inch.
A higher thread count packs more threads into the same inch, so the openings come out smaller.
20×20 is the next weave up, built for insects a mosquito screen was never sized to stop.[2]
Total Screen installs both weaves.
Does A No-See-Um Screen Keep Out Smaller Bugs?
Standard window screens do not stop no-see-ums, and the CDC says so plainly.[3]
The CDC's wording is that many commonly used window and door screens do not have holes small enough to prevent biting midges from getting inside.[3]
A biting midge, the insect behind the no-see-um nickname, is usually less than an eighth of an inch long.[4]
A midge that size passes through a weave a mosquito cannot, which is what the finer mesh is for.
The CDC's own recommendation is to look for mesh screens measuring 20×20, which is the mesh sold as a no-see-um screen.[3]
Phifer, the manufacturer, calls 20×20 a 15-to-20 percent tighter weave that keeps out most smaller flying insects, like no-see-ums, gnats, and sand flies.[5]
Which Mesh Should You Ask For?
For mosquitoes alone, an intact standard window screen is enough.[1]
For no-see-ums, gnats, or sand flies, 20×20 is the figure to ask for.[3]
The County of San Diego names a fine mesh specifically for the small Aedes mosquitoes, which include the tiger mosquito.[6]
Held to the light, the difference between an 18×16 and a 20×20 weave is visible.
Total Screen measures every opening before making the window screen, because a window screen made to the wrong size will not seat flush.
Clearing mosquitoes out of a house is a different job, and our guide explains it: How To Get Rid Of Mosquitoes In Your House.
Get Your Screens Checked Before The Season
A window screen check belongs ahead of the first warm week, before mosquito season starts.
Total Screen repairs, rescreens, and replaces window screens and door screens across San Diego, often with a same day or next day appointment.
A rescreen puts new mesh and new spline into the existing frame.
Call Total Screen at (619) 871-7610 for a free on-site estimate.
Or click here to fill out our 2-question contact-form, and we will get back to you right away.
Can mosquitoes get through window screens? Only where the mesh is torn or the frame no longer seals.
Contact Total Screen to get every window screen and door screen in your home repaired or replaced.
Disclaimer: Total Screen is not a mosquito-control or public-health authority. This article is provided for informational purposes only, and is based on our online research of publicly available documents from the Centers for Disease Control and Prevention, the County of San Diego, and the other sources listed below. To report a mosquito problem, or to ask about treatment on your property, contact the County of San Diego's Vector Control Program.
Sources
- Centers for Disease Control and Prevention — Preventing Mosquito Bites (“Use screens on windows and doors. Repair holes in screens to keep mosquitoes outdoors.”). cdc.gov
- Metro Screenworks — guide to screen mesh (mesh count = threads per inch; 18×16 standard, 20×20 no-see-um). metroscreenworks.com
- Centers for Disease Control and Prevention — Preventing Oropouche (“Many commonly used window and door screens do not have holes small enough to prevent biting midges from getting inside”; “To prevent biting midges from entering your home, look for mesh screens measuring 20x20”). cdc.gov
- Centers for Disease Control and Prevention — Meet the Midge (biting midges “usually less than an eighth of an inch (3mm) long”; “much smaller than a typical fly or mosquito”). cdc.gov
- Phifer — Bug Protection (“15 to 20 percent tighter weave than standard insect screening”; keeps out most smaller flying insects like no-see-ums, gnats, and sand flies). phifer.com
- County of San Diego, DEH — Invasive Aedes Mosquitoes (“Use a fine mesh to prevent the small Aedes mosquitoes from getting in”). sandiegocounty.gov