Awnings that handle the snow
Specialty Fabrics Review | April 2010
Compiled by Juli Case
We had a lot of snow this winter, and now I have a customer who wants an awning that can ‘handle’ snow without collapsing or that can even melt snow. Do those things exist?
We’ve never heard of an awning that can melt snow. It’s an interesting concept, but an immediate concern would be how to protect a heating element (assuming there was one) from the melting snow, or how to drain the runoff that results from melting snow. There’s also the question of how much snow. There’s probably not a way to melt a foot of snow, although while researching this question we did come across a story about a homeowner who tried to melt snow off his awning by using a propane torch. We wouldn’t recommend that to anyone, especially since he set his house on fire and the snow on his awning became the least of his worries.
Rather than melting the snow, a better coping mechanism might be, as your customer put it, an awning that ‘handles’ the snow. Our first thought was to have care with the pitch of the awning: The flatter the awning, the more likely that snow will build up; a steeper awning will help the snow roll off. A second idea has to do with the construction of the frame; if you’re installing in an area prone to a lot of snow, obviously a heavier frame would be in order.
We turned to members of the Professional Awning Manufacturers Association (PAMA) for more specific suggestions.
Many suggested checking the snow load requirements for your geographic area. These can be located in Chapter 16, Structural Design, of the International Building Code.
Several awning manufacturers pointed out that snow on an awning can become a life-threatening matter should the awning collapse. We had respondents who’ve built awnings that can withstand a snow load of up to 70 pounds, but they needed an engineer to determine how to do it. There will be an initial investment to get your designs engineered to withstand a heavy snow load, but once it’s done, you can reuse the designs for future projects.
Specific fabrication techniques used by awning manufacturers in areas that receive a lot of snow include spacing the rafters closer together, using galvanized steel pipe instead of tubing, and adding trussed and welded rafter and front bars. Fabric should be tensioned or stretched tightly so that no ponding can occur. When heat-sealed, stress should be parallel to the heat-sealed seams.
While snow load is primarily an issue dealt with by the awning frame and design, it was also suggested that the type of fabric that you use can also make a difference. A fabric with a slick surface, such as a vinyl material, is difficult for snow to adhere to, and it often slides right off. The higher the tensile strength of the fabric, the less likely it will be to rupture.
As for an awning that melts snow, several PAMA members mentioned clients that use radiant heat underneath the awning to do the job. In fact, one awning manufacturer in New York mentioned that he sometimes encloses awnings for that purpose. Be careful, though, because another manufacturer mentioned that condensation issues can occur as a result of space heaters being used. One awning manufacturer mentioned that the building and planning department in his area won’t accept snow melt plans; the structure has to be built to the snow load requirements in their area.
One awning manufacturer’s spouse is a master electrician and mentioned a product called ‘heat tape’ that is used on roofing and gutters. He reports that it gets to about 40-50 degrees, but that it would need a power source, and that the fabric it’s attached to would need to be flame retardant. We’ve not heard of this being used on awnings before. If you have experience with it, let us know, and we’ll publish the information in a future column.
Not surprisingly, it was an awning manufacturer in Canada who had some experience with an awning that can potentially melt snow. They build a retractable system using two tracks that is reported to be stable in wind or snow. They think that it’s possible to modify it so that an electrical heating beam could be built in the middle of the fabric.
Other snow coping strategies include removing the awning’s fabric for the winter season (which may even be required, depending on the municipality) or to advise your clients to have retractable awnings closed should snow occur. Lastly, even after you’ve designed your awning to withstand maximum snow load, it’s still a good idea to advise your customers to clean the snow off their awnings as soon as possible. After all, as one PAMA member pointed out, even building roofs collapse under the weight of heavy snow.