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amazer 09-17-2007 01:41 PM

Turbine Vents- a good idea?
We just signed a contract with a roofer to install asphalt shingles on our 22 year old cape here in southern NH. The subject of attic ventilation came up, and I have a question for you knowledgeable folks out there.

Our attic is about 40' x 24' and has neither soffit vents nor a ridge vent. All it has is two medium-sized gable vents-- I've attached an electric fan with a thermostat to one of them. The options we are considering are:

1. Doing nothing to change the ventilation.
2. Installing full soffit vents and a ridge vent and removing the fan (which makes a racket when it's on) -- cost about $1,400
3. Adding two turbine vents to augment air flow ($330)

I am wondering which option to pursue. The roofer says that what we have now is probably adequate, but that installing soffit and ridge vents would help keep the lower part of the roof colder in winter, helping avoid ice dams. This makes sense to me, and we have had some ice dams in past winters... but at least I haven't notice actual water intrusion the last 5 winters we've lived here.

I am not sure whether we need both a ridge vent and 2 turbine vents to augment the gable vents. The roofer is a bit ambivalent on this point, essentially saying that the soffit and ridge vent system would be a significant improvement by itself, and the turbine vents would further improve on that.

Also, if we do install both a ridge and soffit venting system, should we plug up the gable vents? I read elsewhere in this site that you don't want open gable vents if you have a ridge vent system, presumably because you want to encourage maximum air intake thru the soffits to keep the lower part of the roof cold in winter.

Can there be too much of a good thing? Should I consider installing two turbines but no ridge vent (which would save me $550)? Or is a ridge vent that much better than a couple of turbines?

That's it for today's conundrum-- any feedback would be greatly appreciated!


FatAugie 09-22-2007 06:56 AM

Let me preface this by saying I'm not a roofer and I did NOT stay at a Holiday Inn last take it for what it's worth.

I just finished replacing my roof and asked a lot of questions in here about ventilation and what have you. The general consensus is if possible, the ridge/soffit combo is a good solution. IF you go that route, you will need to close off the gable ends to avoid a condition where you "short circuit" the airflow from the soffit area through the gable ends. There's some argument as to how much it screws things up, but I wouldn't take the chance.

I had a partially vented soffit where only some of the panels were perforated. I opted to add more ventilation through a product called Smart Vents by DCI products. This was much easier than replacing the panels with vented ones. Check out the website for instructions on how to install.

The thing I would worry about with any mechanical vent solution is maintenance over the life of the item. Motors wear out, bearings seize, etc. and they rarely do it when it's convenient to work on.

Good luck


redline 09-22-2007 12:54 PM

How much insulation is in the attic? What R-value?

Ed the Roofer 09-22-2007 09:57 PM


You learned alot during your short time here! :thumbup:

The roofer doesn't know the proper answer for the ridge vent plus the turbines, but he did provide a valid working scenario with 100 % vented soffits or Smart Vent as Augie linked to and also 100 % continuous ridge vent, preferably, Shingle Vent II, with external wind deflecting baffles.

Read the installation instructions yourself and ensure he is using long enough nails to secure firstly, the ridge vent down and then the shingle ridge caps. I use 2 1/2" hand roofing nails for the ridge vent if the old shingles are removed, but 3" would be acceptable too.

For the longest life of your new shingle roof investment, please do yourself the favor and install the intake and the exhaust vetilation 100 % continuously, and close off the gable vents and eliminate any thought of adding additional whirlybird or turbine vents.


the roofing god 09-22-2007 11:42 PM

do the ridge and soffit vents,but forget about the turbines as they`ll just draw air from the ridge vent openings and defeat the cross ventilation you want:yes:

amazer 09-24-2007 08:24 AM

Thanks guys for the feedback. After doing some more reading and consulting with my roofer, we decided on an approach.

It was clear from comments in this forum that gable vents would short-circuit our soffit/ridge vent system, so we're gonna plug them up. We're also not going to use a turbine vent, since it shouldn't be necessary with our full ridge vent and the mechanisms are subject to needing maintenance, as was pointed out earlier in this thread.

I printed out some pages from the DCI Products site (makers of SmartVent) and my roofer liked their design for soffit intake, so if we can find a local distributor, I guess we'll go with that product. If not, he'll install conventional vents along the soffits.

Thanks for your help!

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