In an ideal world, we’d open our windows all summer and close them all winter, worried only about saving money on our energy bills and feeling comfortable in our homes.

But we do not live in this ideal world. We have pests here. A lot of them. And leaving the window open typically means that some bugs are going to get inside.

Most of us try to prevent this by using mesh window screens, which are designed to allow air flow while also keeping bugs out. But you may have noticed that these screens do not always work.

Why?

Common Ways Bugs Get Through a Window Screen

Even if a mesh screen is brand new, it does not guarantee complete protection against insects. Bugs can enter in many ways including:

• Gaps Around the Frame – One of the most common reasons bugs get inside is small gaps between the window frame and the screen. Even a slight misalignment in installation can leave enough space for tiny insects to squeeze through.
• Mesh Size and Bug Size Mismatch – Not all screens are designed to block the same types of insects. Standard window screens typically have a mesh size of 18×16 (18 strands per inch in one direction, 16 in the other), which is enough to block larger bugs like mosquitoes. However, smaller insects like gnats and no-see-ums can slip through finer openings.
• Torn or Stretched Mesh – Even though the screen is new, slight damage can occur during installation or everyday use. A small tear, stretched mesh, or frayed edge may create an opening that insects can exploit.
• Improper Sealing Around the Edges – Some window screens use a rubber spline or adhesive to secure the mesh within the frame. If this seal is not tight or has minor gaps, bugs may crawl through the space where the screen meets the frame.
• Bugs Entering When the Window is Opened – Even if the screen itself is secure, insects can enter through other means. Bugs may cling to clothing, enter when the door is open, or find their way through small openings around the window frame or vents.

Often times, you can’t see that there are small openings around the window screen, or you assume that the hole in the mesh is not big enough for pests. But a spider needs only a few millimeters to get inside. A fruit fly can be small enough to get through the mesh, let alone a tiny, barely perceptible opening around the edges of the screen. Bugs are less likely to get in, but they absolutely can get in.

Preventing Bugs from Entering Through a Window Screen

While a new window screen reduces the number of insects that enter, additional steps may be necessary to improve protection. For example:

• Checking for Gaps and Sealing Openings – Inspecting the edges of the screen and window frame for small gaps and sealing them with caulk or weatherstripping can prevent insects from squeezing through.
• Using a Finer Mesh Screen – If smaller insects are getting through, replacing the screen with a finer mesh, such as 20×20 or higher, can help block smaller bugs like gnats and midges.
• Installing Bug-Proof Window Seals – Some window designs allow small gaps where bugs can enter even if the screen is intact. Applying foam weatherstripping or additional sealing around window edges can minimize these openings.
• Keeping the Surrounding Area Clean – Bugs are attracted to light, food, and moisture. Keeping lights dim at night, removing food sources near windows, and using insect-repelling plants or sprays can reduce the presence of bugs near the screen.

A new mesh window screen provides a strong barrier against insects, but it is not always a perfect seal. Regardless, there is simply no substitute for professional pest control, and while we can’t stop all bugs from going through an open window, we can make sure they won’t survive. Contact us today to learn more.