Gable vents alone are not enough. Is that what is there now? Is there insulation in the roof rafters or ceiling joists? Personally, I would use soffit vents, and ridge vent and ice and water shield the entire roof.

Only gable vents at this point, the house was built in the 60s. The roof is very old, so we need to update with a ridge vent or attic fan. Just want to make sure we have proper ventilation for our roof.

I would leave the gable vents, make sure that the screen is good on them. I dislike ridge vents, but, I do like the fans. You could also add vents to the back side of your roof.

Because of construction differences there is no single best way. When possible I go with soffit plus ridge vents. Passive trumps power any day.

Powered roof vent fans can actually harm venting of an attic. Those that jump right to using them do not understand attic ventilation. Roofers are generally not versed in it.

Standard operating procedure with re-roofs today for any roofer is adding a ridge vent, whether there is already existing ventilation and/or you need it or not. It can also have negatives, but not cause as much potential harm as powered fans can.

The best scenario of passive attic ventilation, and one you always try for, is continuous low intake air at the eave, and continuous high discharge air at the ridge. So soffit vents and a ridge vent.

What I would ask is are your existing gable vents performing appropriately, do you have eaves that would allow soffit vents, and are your roof massings positioned for ridge vents.

For a typical asphalt shingle roof slope with simple design, I would not put Ice&Water Shield over the entire roof. It is certainly for eaves and valleys, the remainder I would want the sheathing to breathe.

Turbine vents do not require power, and move a lot of air if it's windy. They are very common where I've lived in ND and MN.

Turbines are very common in my area too.

Turbines are indeed a common sight on rooftops but monkey see,monkey do isn't necessarily good policy. If you have access to rooftop turbines, I have a suggestion. Go into attic and observe volume and velocity of air movement at intake of turbine. Unless it includes a radial fan,there isn't much air movement. I dare say discharge volume would be slightly increased by removing turbine from jack. (Not necessarily a permanent arrangement due to rain intrusion but a convincing demonstration.) Ridge vents are the better choice. No method works to potential unless there's adequate soffit vents that are not COVERED by insolation. Don't laugh, you would be amazed how often insulation blocks air path between rafters above top plate.

Turbines are a poor solution to residential passive attic ventilation. They are conceived for pole barns when you want some air movement but don't need attic ventilation. A roofer that recommends those has let the industry and science pass them by.

Here's an analogy that might visualize it: Picture a 70,000 seat football stadium at capacity, and each person is a little pocket of air.

When the game's over, there are 2 turbine fans as the only exits. Each fan can move 10,000 people, but the rest have to wait to funnel through their turbine fan, sitting and waiting in the corners of the stadium.

Now, let's say those turbine fans are electrically powered fans instead. Not only do the people have to wait for the fans to turn on to get through them, so they can't exit at halftime, those fans will then suck people back into the stadium that have already reached their cars in the parking lot.

The best scenario of this stadium is many, many little doors all around the building, even though each can only pass 1000 people, everyone gets out quick and continuously like a ridge vent.

I live in the Chicagoland area, and we can have very harsh winters. When I replaced my roof, I had two courses of ice and water shield installed. While I can’t address your other concerns, I would strongly encourage you to have the whole roof covered with ice and water shield. It can give such peace of mind in preventing ice dams.

As windy as it is here (believe me, Chicago has nothing on the Red River Valley), turbines do quite well, especially in winter. Snowed over ridge vents can create ice dams.