Metal roof

[mneck1814]

I never have to shovel my roof. The guards are just to control the snow dumping in front of the doors, the small area (maybe 10 feet of roof) melts pretty quickly after a storm and everything else slides off. I don't have the problem with snow getting stuck in the valleys, the snow slides from those, too. Where the snow comes off onto the deck I do have to shovel that relatively soon after it comes off the roof before it freezes solid, I have always shoveled the deck after a storm anyway.

[SIKSUKR]

Shoveling snow off your roof is one of the biggest mis-hypes by the media. Most homes in this part of the country have to be built for snow load. While not true in all cases, it pretty much depends on the pitch and the size of the framing. Very flat roofs should at least be cause for concern but the normal northeast pitched roofs are just fine. I prefer to have that snow on my roof as it is great free insulation. And as has been addressed prior in this thread, another big misinformation by the media is after big snowfall they love to tell you that the warm temps will be adding weight so get that snow off now. Rain, of course is a different story but for those with flatter roofs, be happy if warm weather follows because any melting will lighten the load.

[Happy Gourmand]

Originally Posted by SIKSUKR

Shoveling snow off your roof is one of the biggest mis-hypes by the media. Most homes in this part of the country have to be built for snow load. While not true in all cases, it pretty much depends on the pitch and the size of the framing. Very flat roofs should at least be cause for concern but the normal northeast pitched roofs are just fine. I prefer to have that snow on my roof as it is great free insulation. And as has been addressed prior in this thread, another big misinformation by the media is after big snowfall they love to tell you that the warm temps will be adding weight so get that snow off now. Rain, of course is a different story but for those with flatter roofs, be happy if warm weather follows because any melting will lighten the load.

I agree. For the most part, I think you are likely to cause damage to a roof by shoveling it. Not only by hitting it with the shovel or anything else, but by possible damaging the shingles by walking on them when they are cold and brittle.
Of course there are exceptions...flat or near flat roofs built before current standards could be cause for concern. Otherwise, like Siksukr said, take advantage of the extra insulating value of the snow cover.

[DickR]

While the durability of metal roofing is one thing, there are the issues of snow sliding off it to places you'd rather it not pile up. If you are building a new house and think that you ought to have a metal roof so you can avoid having to shovel snow off it, think again. As pointed out, the roof must be designed for a heavy snow load, so for a new house there isn't anything particularly wrong with letting the snow stay there.

If the intent is to avoid ice dam formation and excessive icicle formation, bear in mind that in nearly every instance the formation of ice dams and icicles is an indication of heat leaking into the space under the roof deck. For a new house, there is no reason why this ought to happen, if care is taken to avoid this sort of heat leakage. Take care to seal the upper level ceiling against air leakage into the attic space. Avoid can lights there; they are a bad idea, from a building science point of view. Provide adequate soffit and ridge ventilation. Keep the heat out of the attic and you avoid roof ice issues.

For a lot of good information on this sort of thing, a good site to browse is www.greenbuildingadvisor.com.