Screen Mesh Openness Factor: How to Choose 1%, 3%, 5%, 10% or 14%
Openness factor (OF) is the percentage of a screen fabric's area that is open holes between the yarns. A lower openness factor blocks more sun, glare, UV and visibility; a higher one keeps more view and airflow. For most patio and porch screens, 3-5% is the best balance; choose 1% for low western sun, strong glare or daytime privacy, and 10% or more when keeping the view and breeze matters most.
Key takeaways
- Openness is about holes, not color: a 5% charcoal and a 5% white mesh have the same open area but look and perform differently.
- Direct sun through the holes is never filtered, so the maximum UPF is roughly 100 divided by the openness percentage.
- Dark colors give the clearest view out; light colors reflect more heat but glow and reduce visibility.
- Daytime privacy works because outside is brighter than inside; at night with lights on, it reverses.
- When in doubt, go one step lower in openness and darker in color: you can recover view with color, but you cannot add shade later.
What openness factor means
Solar screen fabrics are woven from yarns of PVC-coated polyester, fiberglass or similar, with deliberately regular gaps. The openness factor is the gap area as a percentage of the total. Phifer and Twitchell are well-known US makers of these meshes; European suppliers such as Serge Ferrari, Mermet and Copaco make equivalent fabrics. Common openness steps are 1%, 3%, 5%, 10% and 14%, with some ranges offering 2% or 4%. Definition: openness factor in the glossary.
Solar mesh is not insect screen. Standard insect screening (often 18 x 16 strands per inch) is mostly open and offers little shade; tighter "no-see-um" meshes stop smaller insects but still are not shade fabrics. Many solar meshes at 5% or below also keep out most insects. The trade-offs are covered in solar screens vs insect screens.
Openness factor at a glance
| Openness | View out | Glare control | Best-case UPF | Daytime privacy | Typical use |
|---|---|---|---|---|---|
| 1% | Limited, silhouettes | Excellent | 50+ | Strong | West and southwest exposures, outdoor TV, privacy |
| 3% | Fair | Very good | About 33 | Good | South and west patios, general use in hot climates |
| 5% | Good | Good | About 20 | Moderate | The default balance for most porches and patios |
| 10% | Very good | Moderate | About 10 | Low | East and north sides, views, mild climates |
| 14% | Excellent | Low | About 7 | Minimal | Airflow and light insect control with a view |
UPF ceilings follow from the open area; real values are slightly lower in light colors. See UPF and UV protection for the reasoning.
Color changes view, heat and glare
Two screens with identical openness behave differently by color:
- Dark colors (black, charcoal, bronze, brown) absorb light, so the yarns disappear to the eye and you look through the holes. They give the clearest view out and the least glare. They absorb more solar energy, which mostly dissipates outdoors on an exterior screen.
- Light colors (white, beige, light gray) reflect more solar energy away, which helps heat rejection, especially on exterior screens over glass. But the sunlit yarns glow, which reduces view-through and can raise glare inside.
- Mixed or two-tone yarns (gray/white, charcoal/beige) blend the two behaviors and often match house trim better.
Privacy by day and by night
Screens give privacy through brightness contrast, like a one-way mirror. In daylight the outside is often many times brighter than inside, so people outside see the bright reflection of the mesh, while you see out through the holes. After dark, with lights on inside, the effect flips: neighbors can see in, and you see mostly your own reflection.
- For daytime privacy from a street or neighbor: 1-3%, light or mid color on the outside face.
- For night privacy: no solar mesh is enough; add a blackout or "privacy" fabric, or a second screen.
- For a covered porch used mostly in the evening: openness matters less than lighting placement. Lights aimed down and away from the screen reduce the see-in effect.
Choosing by orientation and latitude
Low sun is the hardest sun to stop with an overhead awning, and it is exactly what vertical screens handle well. In the Northern Hemisphere:
- West and southwest: intense, low afternoon sun at the hottest time of day. Choose 1-3%.
- South: high sun in summer that an overhang or awning partly blocks. 3-5% usually suffices; see the shade calculator to check how much the roof or awning already covers.
- East: morning sun when air is cooler. 5-10% works for most.
- North: little direct sun. 10-14% for view and air, or insect screen only.
The screen selector walks through these choices with your site details.
Wind and airflow
A lower openness factor makes the screen behave more like a sail. A 1% mesh passes little air and takes a higher wind load than a 10% mesh, and it cuts breeze through a porch noticeably. For tall or wide screens in exposed spots, the fabric edge retention matters more than openness: zip-track systems lock the fabric edges into the side channels so the screen does not blow out. See zip-track screens and wind resistance.
Worked example: a west-facing lanai
For screen types and drive options, see the retractable screen guide and motorized patio screens.
Frequently asked questions
What openness factor is best for a patio screen?
For most patios, 3-5% in a dark color. Use 1% for harsh west sun, outdoor TVs or daytime privacy, and 10% if you mainly want insect control and a view.
Does a lower openness factor keep it cooler?
Yes, mainly by blocking more direct sun. On exterior screens over windows, a lighter color at the same openness also reflects more heat away from the glass.
Can I see through a 1% screen?
You can see shapes and movement outside in daylight, but detail is limited. It is closer to a sheer curtain than a window.
Do solar screens keep bugs out?
Most solar meshes at 5% or lower keep out typical insects when the screen seals at the edges and bottom. Very small insects may pass larger openings, and gaps at the edges matter more than the mesh.
Is openness factor the same as the percent of heat blocked?
No. Openness is open area only. Heat blocked also depends on how much the yarns reflect and absorb, so a light 5% mesh can reject more heat than a dark 5% mesh even though both have the same holes.
Can I use screen mesh as awning fabric?
Yes, on drop-arm awnings and some vertical or angled shades. On lateral arm awnings it is less common because mesh lets rain straight through and gives lighter shade.
Sources and standards consulted
- AATCC TM183, Transmittance or Blocking of Erythemally Weighted UV Radiation through Fabrics (AATCC)
- AS/NZS 4399, Sun protective clothing: evaluation and classification (UPF) (Standards Australia)
- ASTM D6603, Standard Guide for Labeling of UV-Protective Textiles (ASTM International)
- EN 14501 and EN 13363, Solar protection devices: thermal and visual comfort, solar transmittance (CEN)
- Awning fabric technical data sheets from major acrylic and polyester mills (manufacturer documentation)
See how we research for our sourcing and verification process.