I just got a new roof from the hail storms in Dallas a couple months back. The roofer was supposed to install a ridge vent and turbines, but didn't install any turbines. I did some "very scientific" research thanks to google, and I read that ridge vents are largely ineffective without soffit vents. Is that true? Do turbines work without soffit vents, and are they more effective on their own than ridge vents?

I saw the other ventilation thread about 6 pages back, but wasn't exactly what I was asking.

Ridge and or turbine vent does very little without soffit vents to pull from.

[This message has been edited by JP76 (edited 8/2/2012 8:20p).]

Maybe you already have soffits but do not know it?

My own personal opinion, without a vast sceintific research base, is that ridge vents are really only good for fast, easy installation and water leaks. Soffit vents, gable vents and turbines really move air!

Ridge vents are teh way to go.
You roofer had nothing to do with soffit vents. You most likely have a hardi soffit with preforated holes in them.
A ridge vent and a turbine vent is redundant. You don't need both.

See pics for 2 types of soffit vents.

Do you have gable vents?

I do have gable vents on the two sides of my house, no soffit vents. And thank y'all for your responses.

So how does one get soffit vents, when they have none.

You can cut a bunch of holes with a saw and put them in; that's what Mr Dubi did at our rent house. I'll try to take a pic in the morning.

I have a gabled roof with large gable vents. Would it help to add soffit vents or are we getting enough airflow from the gable vents?

Adding ridge vents where there are gable vents is not recommended, as the air just "short circuits" from the gable to the ridge.

The currently-accepted formula is 1/150. Where you divide the floor area of the entire attic by 150. Thus, for 3200 sf of attic, you'd 3200 ÷ 150 = 21.33 square feet. half of that to be intake, half exhaust. Typical ridgevent is 18 square inches per lineal foot. Our putative 21.33 / 2 is 10.66 * 144 = 1536 sq. in., or about 84 lineal feet of ridgevent.
Those rectangle vents are only about 56 sq.in. each--28 in out example. Continuous soffit vents run from 12 to 120 sq.in. per foot.

However, Building Science research shows that the 1/150 ule is about like rolling your car windows down two-fingers' worth. Like rolling down the windows in your car 1-3/4 to 2" there is some effect, about 4-5º temperature reduction. In Texas, 1/150 attic ventilation produces the same result, 4-5º temperature cooler. So, instead of hitting 140º you attic drops to a frigid 135º

Given how much infrastructure we run in the attic, it's really a lot better to extend the insulation plane up the walls and under the roof. In retrofit this introduces a need for changing how combustion air is supplied, but that is a surmountable detail. One very much offset by not having ventilation ducts in 130º attics (that R5-6 blanket is only keeping the duct air down to 124-126º).

Yes you need soffit vents. Possibly more than you used to have or whatever exit vent system you use will not help.

Agree with Cap. having multiple upper vents, turbines, passive, ridge, gable, will "short circuit the purpose.

If you add soffit vents you must use the baffles to make sure the air gets past the insulation. The second picture above is more ideal. This is common in newer construction. But, again, without proper baffles, it is not helping.

Also agree with Cap that most of these measures, and the code are very slightly better than nothing. Unfortunately, the more effective solutions are generally cost prohibitive.

Check out the pics I posted in the foam thread, to see what it does to attic temps......

Interesting thread and very timely. We're about to get a new roof in Lake Highlands and I was thinking about having them add a ridge vent (we have a ridge that runs the entire horizontal span of the house). We have two gable vents and no soffits, so maybe, based on the advice here, I will scrap the ridge vent. I think we only have 3 turbines.

Dittos on needing soffit vents. Hot air rises and when the turbines turn or it exits the ridge vent, the "vacuum" will pull cooler (or less hot) in via the soffits.

"It is better to trust in the LORD than to put confidence in man," Psalm 118:8.

Yes to soffit vents / no to whirlybirds since you already have ridge vents.

My hubby installed these a few years ago when we repainted. They go the entire length of the house on both sides. We also got a thermostat controlled fan braced next to a large gable vent and force the hot air out of the attic. The attic is much cooler now.



[This message has been edited by Dubi (edited 8/10/2012 9:52p).]

I need to post pictures of the underside of my roof. the soffit is a little mesh piece that goes right up next to the attic space, but doesnt cover the majority of the overhang so I see nails everywhere on all sides of my roof. It's horribly ugly.

Guessing I should add this to my project list.

Ah, what you need is a product called Cor-A-Vent. This is a vinyl-plastic material which bears a strong resemblance to corrugated cardboard (hence the name).

It's available in a number of thicknesses and widths. The "tubes" in the corrugations are small enough to let air pass through, but not vermin so very much. Being a rigid material, it can be nailed through, and still provide ventilation.

Here were we use so much veneer face brick, a slick way to get near-continuous soffit venting, is to take down the brick mould, install the Cor-A-Vent, and re-install the moulding. The material is black, so, it mostly resembles a shadow-line rather than an overt vent.

It's about the only way to vent dormer roofs and similar low/no overhang soffit/fascia.

That is, if one is committed to ventilating such spaces.

It is not true that ridge vents are not effective without soffit vents. This set up is very effective at driving up your utility costs. Attic ventilation, when done well takes advantage of stack effect, which is the natural tendency for hot air to migrate up. If you do not have adequate soffit vents, the vented attic air will be replaced with conditioned air out of your house. In most homes there are many places that air can escape from inside the house to the attic. the 1:150 ratio is a very gross approximation of how much ridge vent you need. it does not address how much soffit vent you need. Our company does energy audits and retrofit. We recommend at least 30% more unblocked soffit vent area than ridge vent area. Do not judge your soffit vent area by the outside size of the soffit vent. We have seen builders put soffit vents up without cutting an opening and it is not uncommon for the opening to be significantly smaller than the vent.

Hugh Stearns
President
Stearns Design Build
StearnsDesignBuild.com

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The attic is much cooler now.

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That's b/c you are pulling cold air out of your house and into the attic thru the many openings in the ceiling.

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We recommend at least 30% more unblocked soffit vent area than ridge vent area.

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Can you have too many soffit vents?

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That's b/c you are pulling cold air out of your house and into the attic thru the many openings in the ceiling.

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Our A/C bill went down after we installed the soffit vents and attic fan. If we truly were pulling cold air out of the house, our bill would have gone up to keep the house the same temp.

[This message has been edited by dubi (edited 8/14/2012 12:16p).]

Nm

[This message has been edited by hotardag07 (edited 8/14/2012 4:24p).]

We just added 6 more soffits to the front for a total of 20, and along with radiant barrier and 2 turbines on a huge multi-peaked attic, it was 91 in there yesterday at 5:30 PM, not bad.

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Our A/C bill went down after we installed the soffit vents and attic fan. If we truly were pulling cold air out of the house, our bill would have gone up to keep the house the same temp.

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Not necessarily. If you had ZERO attic ventilation before, you now have some which will make it go down. But you could still be pulling air out of the house.

Air will take the path of least resistance. Go into the attic, close the attic stairs, turn on the vent fan and feel around any openings (lights or AC vents) and see if you can feel any air moving. Especially check at area's near the fan. It's much easier for air to move from a light in the ceiling to the fan than from a soffit vent 20-feet away. Also check around the attic stairs.

So i moved into an older house with no soffit vents or powered/traditional attic vents. pretty easy to install something like these:
http://www.lowes.com/ProductDisplay?partNumber=269916-228-NPSP8WW&langId=-1&storeId=10151&productId=3122395&catalogId=10051&cmRelshp=req&rel=nofollow&cId=PDIO1

plus soffit vents?

It does no good to have more soffit vents than exhaust vents. You have to have a balanced system. It won't hurt anything but your wallet putting them all in. You could put 1000 soffit vents, but if you have 10' of ridge vent it will only allow so much air to pass through.

Cap was right about the short circuit. Have 1 type of exhaust vent per section of the house. If not, the peak of your roof will be nice and cool, but there will be no air movement throughout the rest of the attic.

I have a house built in 1955 that has no ridge or attic vents or soffit vents. Just one gable vent.