Replies

1. 
   Dana1 | Apr 02, 2016 02:25pm | #1

   Active ventilation would be more likely to create rather than solve ice dam problems, and may even cause other problems.

   Ice damming is a symptom of heat leaks. It could be air leaking into loose insulation from the drywall cracks, insufficient insulation at the top of the walls, or insufficient insulation in the vaulted roof, air leaks from conditioned space into the rafter bays via other paths, such as wall cavities, flue/plumbing chases, etc.

   A common solution is to put sufficient insulation above the roof deck, and dense-pack the rafter bays with fiber insulation. To advise more specifically required more information, such as the location (or US climate zone), the rafter depth, the insulation levels, the presence or absence of any vapor barriers in the ceiling, etc.

2. GBA Editor
   Martin Holladay | Apr 03, 2016 04:39am | #2

   Rick,
   I agree with Dana Dorsett -- we need more information about how your roof assemblies are insulated, and where your house is located.

   It's possible to build an unvented roof (one without soffit vents or ridge vents) that performs well. Here is a link to an article that explains the right way to build an unvented insulated roof assembly: How to Build an Insulated Cathedral Ceiling.

   Since your roof is plagued by ice dams, however, it's clear that your roof does not perform well. Here is a link to an article that explains what you need to know about ice dams: Prevent Ice Dams With Air Sealing and Insulation.

   Until you tell us more about your roof, it's going to be hard to give advice. But the usual remedy for an unvented roof plagued by ice dams is to install one or more layers of rigid foam above the roof sheathing, followed by another layer of sheathing (plywood or OSB) and new roofing. Here is a link to an article with more information on that work: How to Install Rigid Foam On Top of Roof Sheathing.