Channel Drain corrugated roofing is a good design in preventing water from penetrating beyond the overlap. Any water that may get by the first ridge at the lap gets whisked down the drain channel. The result is no leaks even in driving, wind-blown downpours. With washered screws as fasteners in the flat sections, the roof should be completely waterproof, a vast improvement over what it was with nails loosening enough to expose holes to the weather.
Even Channel Drain can’t prevent ice dam leaks, but with the new venting system creating a cold roof, ice dams should be less of a problem.
To keep critters out, a contoured foam strip was added under the bottom edge of every panel. This step is often omitted but there is no need to invite wasps to live around people.