[jjl3rd]

I too had an ice dam problem and my ridge vents were augmented by vents on the gable end. I never thought that the problem was that the ridge vent was blocked so I did not test to see if unblocking would help. What I did do was two fold both of which worked. first I put some of those heater wires up and down across the area where the dam formmed. that allowed the roof to drain and stopped my leaky ceiling problem. Next I added another layer of insulation to the ceiling ( being careful not to block the air flow from soffit to ridge). After adding the extra insulation I found that I no longer needed to melt the dam as it would no longer form. The addition of the insulation in my case was a long process the wires were much easier but dont save on the heating bill. Since it is already winter I would first add the wires then when time permits add more insulation.