And the Answer is: Do Not Vent
The working theory for many
years was that wind vents would reduce the wind load on any given banner. In
other words, wind would blow threw instead of pulling on and possibly tearing the
banner. This theory was so widely accepted that some governments made vents
mandatory for banners installed in certain locations. Springville, Utah went as
far as to regulate that at least 20% of the area of a banner must be made up of
holes.
But, wind tunnel tests conducted by aerodynamic specialists not only disproved the theory that slits, flaps or
holes will reduce wind resistance but have scientifically proven they can be a detriment
due to vibration and fabric stress within the banner. They tended to
increase the wind load rather than reduce it. "The holes allow the fabric to
ripple and catch more wind increasing the drag factor.” [i]
The aerodynamic specialists concluded
(somewhat tongue in cheek) that “if you have a banner tied in such a way that
it will remain flat in the wind, then it seems that the benefits of adding
vents are minimal unless you want to make your banner into Swiss
cheese.”
Here in the city and county
of Denver, while permits are required for some outdoor signage, the city doesn’t
dictate vents or no vents. That stated, to recommend the best substrate we
always ask our clients about the install location of the banner and how long
it will be up. Based on the research and our professional experience, SpeedPro
Denver suggests a few materials that work with the wind without marring your
design with holes. Here are a few examples:
Scrim: Commonly used for outdoor signage
since it is scratch- and
water-resistant but can be penetrated for grommets for easy
hanging. Scrim banners are made of vinyl and reinforced with polyester cording.
The material construction is what gives it strength and durability. Its smooth,
flat finish makes this surface ideal for large-format inkjet printing.
Heavy duty:
Ideal for fluttering flags that will go
with the wind instead of fighting it, this vinyl substrate has high tear
resistance due to the multi-layer design. Typically hemmed and with grommets,
it is also ideal for prints that will be inserted into re-usable stands to
announce the current sale or holiday specials.
To read more about
the research referenced in this story, click the link below.
For a quote or to
talk about your job, give us a call at 303.426.4199, email denver@speedprodenver.com
or visit www.SpeedProDenver.net
To see and read about more banner jobs we’ve done,
check out our Studio News
and view our extensive portfolio!
[i]
“Do wind vent holes in banners make a difference? We used a wind tunnel
to find out” article
published by Novella April 2016, Matthew Mason, The University of Queensland
and Jonathan Roberts, Queensland University of Technology https://blogs.qut.edu.au/science-engineering-education-research/2016/04/25/do-wind-vent-holes-in-banners-make-a-difference-we-used-a-wind-tunnel-to-find-out/
