Turbines vs Powered Attic Fan

I own a construction company, we started out as just roofing and gutters and still do them weekly.

In 6 years I have not installed a single power vent. I have replaced about 100 broken/not working ones though. I wouldn't put one on my house.

I prefer a ridge vent but your roofer is right, ridge vents are best on longer runs. They can be fine on shorter runs but a turbine is the better option on short runs. I've seen numerous roofers not cut the osb back far enough on ridge vents though and that is what is causing the issue, not the ridge vent itself.

Turbines are perfectly fine and work good, but I wouldn't install one while keeping ridge vents. They will work against one another if you have ridge vents near your turbines. If you are putting them on the same slope of your house, I'd get him to quote you on removing the ridge vents and installing ridge shingles.

Just the opinion of another roofing contractor.

Yea I mean I like the look of ridge vents the best, and they work the best imo. But they can easily be installed wrong (although they are pretty simple to install). Roofing is a mindless job and unless you have a project manager on the job overseeing, they will cut corners because all they care about is getting the job done as quick as possible.

As far as the hurricane goes. If a hurricane rips your turbine off you're most likely filing an insurance claim and getting a new roof and turbines anyway

Honestly, I don't think ridge vents work well.
Intuition tells me a power ventilator move air out better.

I’ve got a gable roof with 3 turbines on it. Only complaint is they squeak every now and then and one leaks a little with a really hard rain.

Have you done the calculation to determine if you have sufficient passive attic ventilation with the area of your soffit intakes and ridge vent area? Building codes usually require a minimum ratio of 300:1, i.e., 1 sq ft of ventilation area to 300 sq ft of attic area, equally divided between area of ridge vent (exhaust) and soffit vents (intake). For example, 3000 sq ft of attic area = 10 sq ft of ventilation, 5 sq ft of ridge vent and 5 sq ft of soffit intake. Some jurisdictions require a 150:1 ratio.

I also have an Acadian style house with steep roof, relative short ridge vents on the main facade, not the wings, and I found I far exceeded the 300:1 and 150:1 guideline ratio for attic ventilation. FWIW, I paid $27 to have this company to determine my ridge vent lengths LINK, and got up in the attic to determine the width of the ridge vent opening, and just did the arithmetic to calculate the area. Calculating soffit intake area was easy enough by counting the number of soffit vents and their area.

Anyway, most building science literature I’ve read recommends against electrically powered attic ventilators. When operating you are putting the attic under negative air pressure and though the make up air is supposed to come from the outside soffit vents, unless you have a tightly sealed attic (drywall plates sealed, all electric and plumbing vents sealed, etc), some of that make up air being drawn into the attic is going to be from your cooler conditioned living area below - so you are potentially using at least part of the AC cooling your living area to cool your attic. Additionally, the power ventilators can draw make up air from the existing ridge vent area - hence the often seen recommendation of use one or the other but not both. So as Garcia said, placement of additional attic ventilation devices is important so as to not interfere with function of the existing ridge vents.

Anyway, something to think about before you pull the trigger on adding additional attic ventilation. But I hear you - the short ridge vent lengths on some Acadian style homes can be a problem with attic ventilation.

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I wonder if they are doing much more than I can measure with google maps?

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Google maps is fine - I actually used the aerial service more to determine roof area for a potential DYI radiant barrier install which I’ve not decided on.

You do have short ridges but I’d run the numbers any way just see where you stand relative to ventilation guidelines. But based on what I’ve read, you’d be better off with turbines vs power ventilators, but what I don’t know is if you block/close the ridge vents on your main roof ridges - you don’t want turbines to be pulling through those vents into the attic as those are attic air exhaust areas - seems that’s what Garcia was referring to relative to placement.

The main takeaway is that attic ventilation, and where air is pulled from to “cool” it, can bit more complex than most people realize, and there is potential for pulling conditioned air inside your home into the attic when the attic is under negative air pressure - you want to prevent that.

Is it Ever Helpful to Use a Powered Attic Ventilator . The author has bonafides - does this for a living in Atlanta, Ph.D. In Physics, and happens to be from south Louisiana. He recently published a book “A House Needs to Breathe…Or Does It?” that I’m reading now.

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Is there a profession that specializes in attic ventilation? Or is it just roofing companies winging it? This topic always gets my attention because I have a hip roof and I know my ridge vents + soffits aren't ventilating enough.

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Seems like the best information/adviceon this subject, from what I gather, comes from residential building energy consultants/forensic building consultants. They come in evaluate problems - they’ll identify problem, suggest solutions, they often don’t do the work themselves, but suggest those that do.

This guy Paul LaGrange in New Orleans has had a call in radio program on WWL 870 for years, this subject comes up all the time on his program. LINK. In a nutshell, he likes ridge vents on roofs with longer ridge lines, turbines on roofs with short ridges, and does not recommend electrically operated power ventilators.

I know this doesn't address your question at all, but has anyone ever tried a false chimney that vents the attic? The "stack" would serve the same purpose as it does in normal fireplaces and stoves, that is - to induce more draft. seems like it would be an aesthetically pleasing way to keep the attic space cooler.

Closing up ridge vents when adding turbines is a bad idea. The idea that the ridge vents will short circuit the air flow is wrong. What's important is the sum of open area through all vents. Cooler air enters through the soffit vents, warms in the attic which decreases density, and rises through the open vent areas. With more vent area, air flow volume increases and attic air temperatures are reduced. I have both ridge vents and turbines for this reason. Short circuiting is a myth. Air flow is always from soffit vent up through all vent openings.