What is a banner "wind vent"? Does cutting holes help in reducing the wind load and prolong the life of a banner?
Here is a common definition and thoughts concerning wind vents:
Wind Slits or Wind Vents - "Small openings cut into a banner to allow the wind to pass through the banner. A large banner without wind vents is really more of a sail. Without vents to reduce some of the wind force on a banner, the banner could rip."
These half circle vents are commonly cut into banners at the request of customer, and it is the common belief that wind vents are effective in reducing the wind load on banners. I am approaching 20 years in the industry, and I have yet to come across a single study where the effectiveness of wind vents has been demonstrated. The effectiveness is mostly in the visual effect of seeing the little flaps in a banner open up in the breeze. In reality only a very small percentage of the wind striking the banner passes through the vent. Any studies I have come across state that wind vents do not significantly reduce the wind load on a banner.
Let's think about this for a minute… If you have a 5' x 20' banner, the surface area totals 100 square feet. In order to reduce the wind load a mere 10%, You would need to effectively reduce the surface area by 1/10th or 10 square feet. That would require either (10) 1' x 1' vents or (20) 6" x 6" vents. Cutting this many vents makes the banner look like "swiss cheese" and message less legible. Each individual vent also creates 2 "stress points" in the banner that degrade the strength of that banner and can ultimately lead to premature banner failure creating a potentially more dangerous situation. Below is an example of a "well vented" difficult to read banner.
We therefore do not recommend wind vents in banners, as we feel that there are better options available. Many cities will not put banners up unless they have wind slits and often include them in all of their design specs. When this happens, we include them at the request of the customer. As they say, "The customer is always right".
We would be happy to discuss this issue if anyone has any comments or questions.