huangyhg

snow melt systems for snow drift on existing roofs?
hello,
do any of you have experience using radiant heat cables or other means of eliminating snow drift loading on an existing building roof? does it work? do codes allow this? any links to websites?
i'd like to use this type of solution, if possible, to avoid extensive joist and deck reinforcement of a very large area with many interferences.
thanks.
-jcali
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we've done similar projects in the past where snow drifting was a problem. what we discovered was that the code has no language allowing you to elminate snow drifting from roofs via melting.
you can melt the snow to avoid drifting that blocks views, exposes windows to snow, etc., but not to avoid the load structurally. this makes sense because in a severe snowstorm you run the risk of power loss and subsequent overload of a non-drift capacity roof.
we have used heat tracing as a method in the past, but only as a last resort. we hook it up to an emergency generator though, to cover the power outage issue. is it a large area or small area? what we have also done is build a "deck" structure directly above the existing structure to offload the existing, with acccessways installed to allow for maintenance etc.
the only code provision i have seen that somewhat addresses this is 1997 ubc 1643. for snow accumulation at eaves, the code says "heat strips or other exposed heat methods may not be used in lieu of this design criterion".
what an early engineer mentor told me, "there is always a bigger one coming". bigger one referring to snow storm, rain storm, earthquake, hurricane, etc.
i think jae said it well. during power outage, likely due to heavy snow and ice!, you will have problems. can you provide temporary supports for the winter season? this is somtimes used in the unheated sunrooms before they are closed for the winter.
do what they did in the older days in new enland, pitch your roofs instead of this "florida" flat roof construction junk, cheap initially but expensive in the long run.
when confronted with your situation, we often design a new platform to go over the top of the existing roof, especially if it is a large area and reinforcing the joists is made more difficult by mech and electrical lines.
when adding on to a building, sometimes we have been able to get the architect to have the addition macth the existing roof height for a distance equal to the drift length and then increase the height of the new roof. that way all of your snow drift stays on new construction.
i agree with jae. if you rely on snow melt, there is an excellent chance you will lose power when you need it the most. i doubt you would get approval from a building official.
melt systems are not allowed to be used to reduce design live loads due to snow, in canada anyways. we have some experience with snow.
thank you all. i appreciate your comments and insight.
-jcali

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