What to look out for when installing a gable attic vent?

Question

My attic needs better ventilation. On one end of the attic it terminates to a room that has a cathedral ceiling, and the other end of the attic terminates at an exterior wall (the main gable). It is about 800 square feet with a shallow roof.There are overhangs on the sides of the house but no sofit vents yet. The only ventilation in the attic, aside from being a bit drafty after standing for ~100 years, is a ridge vent (which seems well done but is buried by snow seasonally).

With so little ventilation, right off the bat it seems more is needed. To make matters worse, there's a shower vent exhausting directly into the attic, and it needs someplace to go. (Thankfully, the attic's woods all look good with only one small and non-structural piece I've seen that aught to be replaced.)

On account of the above, a gable vent seems like a good option to vent the attic and also give me a place to vent the shower exhaust.

What should I look for when getting a gable vent installed or doing it myself? I've done some carpentry but am not confident about cutting holes in my house's shell, and even if hiring it out I want to learn what to look for in a good job. Any tips would be appreciated about what to look for in the gable vent itself, making cuts and installing the gable vent, or routing the shower exhaust out through the gable vent somehow.

Answer 1

It will permit good air circulation. I put in a large one , about 24" from roof peak to the bottom of the vent. My roof had low pitch so the lowest cedar board was over 8 ft long. I used 1X6 cedar boards at about a 30 degree angle with about a 3" overlap ( end view). A little snow would blow in on rare occasion which was handled by laying a piece of plywood on the ceiling joists.

Answer 2

I do not see you needing a big fan; 800-1000-cfm should be plenty. I think it is a good idea especially if you have not venting part of the year. I would recommend a separate and complete vent system for the bath fan through the roof. I also would recommend a clock-timer in the gable fan. In winter run it say 20-mins twice every 24-hrs. In summer it can run all the time.