Among the standard screen mesh sizes include 18 x 16, 18 x 14, 20 x 30, 17 x 20 and 17 x 14. The numbers refer to the number of openings on the wire mesh per square inch. For instance, an 18 x 16 screen mesh has 18 openings across, also called "warp," and 16 openings down, which is referred to as "fill."
Screen mesh wires are made of different materials, including aluminum, fiberglass, brass, stainless steel, vinyl-coated polyester, bronze and copper. The different standard mesh sizes are likewise ideal for different applications. Depending on the size of the openings, screen mesh is usually installed on doors, windows, porches, patios and pool enclosures.
The primary purpose of screen mesh is to keep out small animals, insects and airborne particles, as well as block some of the harmful rays of the sun. The 18 x 16 size is the standard screen mesh on doors and windows and is the preferred size to keep out insects. For larger areas such as porches, patios and pool enclosures, the 18 x 14 size is ideal because it is stronger.
Mesh at the 20 x 20 size is ideal in locations where there is a large concentration of smaller insects. The even smaller 20 x 30 screen mesh size will not only keep smaller insects out, but will block around 65 percent of the sun's rays as well.