Venting a low pitch roof

[Dave Zellers]

I have no idea where this should be posted but I'll start here. I'm not building a workshop but a 3 season porch. It will have a 3 pitch shed roof attached to the house. I want to insulate and ventilate it but I have no knowledge of the new products available. Googling has lead me to Cor-A-Vent but I am not fully understanding how the "Roof to wall" works and would like to hear from folks here who might have some experience re these matters.

Surely lots of folks here have built low pitched shop additions.

And don't even think about telling me to stop calling you Shirley. :D

[Thomas Bank]

Here are their instructions for the product: http://www.roof-2-wall.com/

It works the same as their ridge vent. You cut a slot in the roof and their product is basically a corrugated plastic product that you then shingle over. I’ve used both their ridge and roof-to-wall products with success.

However, 3:12 pitch is their minimum requirement and I’d be a bit concerned with snow piling up over the vent and then exhausted air melting the snow and having it run back into the vent - particularly if there is just a drift at the wall and the rest of the roof is uncovered and in direct sunlight.

[Al Launier]

That Cor-A-Vent is a ridge vent used along the top of the roof's peak.
But first, is the 3/12 pitch roof going to be attached to the side of the house or to the existing house roof?
A higher pitch roof is usually better for snow load support & ice dams. However, as a 3-season room that doesn't include heating there is little danger of ice dams builing up during winters, so the 3 pitch roof, although shallow should work if the span is not too great, or is adequately supported.
What size do you intend for roof rafters & spacing?
Will there be a ceiling for this room?
If the 3-season room will be totally enclosed & unheated, then a roof vent may not be required.
What is the span of the roof? The longer the span the more support is needed for snow loads, especially at the lower roof pitches.
Any chance you could provide a sketch or provide pictures of what you intend?
​Have you discussed this with the local building inspector to get a permit & to determine the local building codes?

[Dave Zellers]

The roof is attached to the wall. Since the room is not heated, venting is not required but I want to vent since I'll be insulating and finishing the room including a wood ceiling on the rafters.

Rafters are 2x10 spanning 12 feet. I've got the structure covered and just picked up my permit. I'm totally familiar with ridge venting but not so much with roof to wall venting.

Seems like this is not much different and the Cor-A-Vent roof to wall looks like the way to go. Also, I'll be using Ice and water barrier under the shingles and I believe that requires venting.