Why intake and exhaust must be balanced
Ventilation is a flow, not a hole count. A ridge vent with blocked soffits has nothing to draw from, so instead of pulling outside air through the attic it pulls conditioned air out of the house through ceiling gaps. That wastes energy and does not cool the roof deck. Roughly balanced intake and exhaust is what makes the system work.
The ice dam connection
This is where it touches gutter work. Ice dams form when heat escaping into the attic warms the roof deck, melts snow from beneath, and that meltwater refreezes at the cold overhang — then backs up under the shingles. Working soffit ventilation keeps the deck near outside temperature so the snow does not melt from below in the first place.
That is the honest reason we do not install heat cable. Cable melts a channel through ice that ventilation would have prevented.
How they get blocked
Most often by insulation pushed too far into the eave during an attic top-up, sealing the intake completely. Also by paint on older perforated aluminum, by nests, and occasionally by a previous soffit replacement that covered the vents rather than reproducing them.
What we watch for
When we are on a fascia or soffit repair we look at whether the vents are open and whether insulation has choked the eave, and we tell you what we find. Reproducing ventilation when soffit is replaced is part of doing the job properly — a solid soffit panel where a vented one used to be creates a problem that will not show up until the following winter.