Questions about attic ventilation!
 

We will be getting a new roof soon. The current ventilation consists of consists of lot of soffits and just two electric fan powered roof ventilators. I really feel the attic is under ventilated.

I am looking at a ridge vent setup. My concern is during a thunderstorm with blowing rain or during the rare winter blizzard, will the ridge vent keep the rain or snow out?

What is the best system? What says the brain trust?

I replaced metal vent with holes in it with Cobra vent ( GAF | Cobra Ridge Vent (Attic Exhaust Vent) ). When I did my roof two years ago. Under some circumstances the metal let rain/snow through. The Cobra so far has not.

metal: Google Image Result for http://www.homerestorationsmd.com/images/ridge-vent-4.JPG

I have the opposite problem, lots of roof vents and no soffits. You need both to take advantage of natural convection and get a nice flow going through the attic.

None of them are totally rain and water proof, but most are pretty good. One particularly nasty winter storm blew snow in through our roof vents, which required it to go uphill and over the internal lip inside of the vent. That's only happened to us once in 5 years. Also make sure your soffit vents are open, it's easy for them to get insulation shoved over the top of them.

I can't imagine a ridge vent letting in a lot of snow or rain. It seems everyone around here (Chicago Suburbs) but me has one and I need one. I did everything but the ridge vent a few years ago when I finished my attic. From what I understand, they're not expensive to install either.

You want continues ridge and soffits vents.

Normally a well designed and installed ridge vent won't let in a drop (in a storm most buildings, in most locations are likely to see). In a rafter type roof system (vaulted ceiling) they are particularly important. As Whipped says, it takes advantage of the natural convection, warm air exiting the ridge and cool air entering the soffit. Without a RV or mechanical aids (fans), the lighter warm and moist air, is trapped up the roof line and minimal air exchange occurs. Cheers

Must keep the forced ventilation (fan/s)...

Yup, use 'cobra' vent continuous along the ridge.

Also make sure the ceiling insulation is not blocking the soffit vent in the eaves. Depending on when your house was built, it may not have baffles to allow air to flow over the insulation.

If you have a hip roof, you'll need a power vent, as there isn't enough ridge for ridge vent. With a gable roof, you can use ridge vent or power vents.

My thought is not to use power vents with ridge vents. All you will do is pull air from the ridge vents and not circulate the air from the soffit.

Go to the cobra vent website, or look up roof ventilation. There is a ratio between roof vent and soffit vent area. Can't remember the exact ratio but, you need more soffit than roof vent area to prevent drawing a slight vacuum on your attic space, and pulling air out of your living space. I had to go with a powered fan because I lacked the required ridge length to get the proper vent area. The PO of my house also short circuited the ridge vent by installing a ride vent on a ridge that was about 3 feet lower. The poor ventilation on my newly purchased home cost me a summer's worth of my time and $7k to replace rotted rafters, sheathing, roofing etc....

My neighbor went with the Cobra Extreme Snow country ridge vent. He has been happy with that. We only get a bad snow storm once or so every other year. We get more blowing rain from thunderstorms. As some HOT summers.

I closed up my ridge vents a couple of years ago and installed 3 temp controlled roof fans. The attic area was under ventilated. Now it is much better. I would like to also install Radiant Barrier in my attic since we have so much southern exposure.

The real solution for me is about 70 x 225W solar panels which will reduce my attic heat-load by about 70%!