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I work for a contractor/building science firm and we are trying to deal with the problem of ridge vents failing to operate when they are covered by snow. We believe that this contributes to severe ice dams every winter, has anyone else seen a similar problem? If so, how have you tried to prevent it in new construction. Thank you very much.
 

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Jon Boy said:
I work for a contractor/building science firm and we are trying to deal with the problem of ridge vents failing to operate when they are covered by snow. We believe that this contributes to severe ice dams every winter, has anyone else seen a similar problem? If so, how have you tried to prevent it in new construction. Thank you very much.
For starters, we don't put ridge vents on any slope less than 6:12. At that slope, snow tends to slide off our aluminum shingles. For other materials such as composition shingles, I would look for a slope of 8:12 or more (in snow country).

The coverage of the ridge vents by snow is just one of the failure points. Inappropriately arranged ventilation (ridge vents plus gable vents, as Grumpy noted in another post) or insufficient intake ventilation at the soffits are some of the other ways ridge vents don't work.

In our area (Montreal) we get lots of snow and most low-profile or mushroom vents get snowed over so the "good" roofers are using a locally-manufactured vent called the Maximum (actually there are several different models) which stands above the typical level of snow. These vents are much better than ridge vents for snow country.
 

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Specialist said:
OT - pgriz, I heard you guys kicked the Expos out.
Not really. We've had a bunch of bad owners that sold off the good players over the years, leading us to be the best farm team in the East. The location in the olympic stadium didn't help. Over the years we've had some good players, but as soon as the fans warmed up to them, they would be sold and the cycle starts all over again. You can jerk around the fan base only so long before people find better things to do with their time.
 

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I work in the ski areas of the Rockies. There must be a horizontal plenum along the ridge....this means that the rafters have to have small "notches" cut out of them. The intake must be equal or greater than the exhaust (ridge). Use the highest profile of ridge vent you can. As snow drifts over the ridge vent, the speed of the exhausting air increases in the non drifted area of the vent. Most of the vent can be drifted over while the velocity of the air venting from the remainder actually "blows" snowflakes away from the vent. I have seen cold roofs with Boston Ridges in Sun Valley, Id with 6' of snow on them and yet they will have a "funnel like" hole through the snowpack to the Boston Ridge. you can feel the air flow coming out of the hole.
Jim
 
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