The Facts About Wind Slits in Banners
What You Need to Know about Adding Wind Slits to Vinyl Banners
We are often asked for recommendations on the topic of wind holes or wind slits in banners. These slits, usually made in the shape of a half circle or half-moon, are typically added with the idea that they wind to pass through the banners, thus reducing the total banner wind load. But this is not the case, particularly for light pole banners and wall mounted banners.
Testing Wind Slits
In 1984 and in 2002, we set up two, full-size wind tunnel tests where we tested the effectiveness of our KBW BannerFlex hardware. During that time, we tested banners with wind slits as well as non-vented banners. In both cases, it was visually obvious wind holes became detrimental to the banners due to vibration and fabric stress within the banner. The wind slits tended to increase the wind load rather than reduce it.
How Can Wind slits Increase Load?
- The holes set up vibrations when the wind goes through the holes, similar to organ pipes. The vibrations can affect the life of the lighting fixture or light pole and may well be detrimental to the pole and its base over the long term. However, using fiberglass arms WITHOUT wind slits deflected more wind indicating more force on the system with the holes than without.
- Wrinkles are created in the banners between the holes that actually capture more wind which puts greater force on the mounting brackets and light pole.
- Wind holes typically put into banners are usually 3 to 5% of the banner surface area. For example, six (6) 6”diameter “half-moons” cut into a 30” x 94” banner represent 3% of the surface area. The greater number of slits, the more vibrations and more wind is captured.
Based on these findings, we do NOT recommend wind holes or slits to our customers for wall mount and light pole banner installations. For maximum wind reduction, choose a fiberglass arm with an adjustable bracket.
Want to know more about our wind testing? Check out our Wind Test Calculator.