Attic venting

[Christopher]

Greetings all,
I'm a newbie on this thing. My present project involves gutting the attic of my bungalow and putting in a bedroom, bath, and office. Built circa 1924, the home has little ventilation (the previous owner installed a Cobra ridge vent but no eave venting). Since I am drywalling along the rafters, I would like to get some circulation behind there and install some venting under the eaves, which are aluminum-siding-over beadboard. Any suggestions? The home stores have not been helpful. I've found some rectangular louvered vents but I thought a 4" circular vent might be available so that I could get away with using a hole saw instead of having to cut 48 rectangular slots. Thanks.
Christopher

[Rich]

There are 2" round vents that should be pretty easy to get.

[grumpydasmurf]

Check www.rollvent.com and www.airvent.com They have some good rules of thumb for intake and exhaust.

2" continuous is great for intake usually. Two passes with the circular saw and your ready to install. If you don't vent continuous then your going to have to place a vent every 16"-24" because some rafters will become blocked and un-ventilated and placing vents every 16-24" will look tacky. Go for the 2" continuous.

If you are installing a ceiling at the bottom of the rafters, I HIGHLY recommend what is called rafter baffles. The reason is you are probably going to insulate the rafter pockets and the insulation touching the bottom of the roof deck will block air flow. It will also retain mousiture and cause mold against the wood roof deck.

I am certified by AirVent and have to correct attic ventilation issues damned near weekly.

[Christopher]

Thanks much for the input. Yes, I was planning on using baffles prior to insulating.
Back to the soffit vent however, I checked out the airvent website and saw the continuous product offered. As tempting as a two swipe cut with a circular saw sounds, I would be cutting through both bead board and aluminum siding. Could this become an unsightly mess after tacking on the soffit vent? My eaves are about 17" with the aluminum siding running perpendicular to the house, so I'm not sure how aesthetic any solution might be (and the rafters are 24" on center). I appreciate your expertise, so advise away.

Christopher