Soffit Venting - is there such thing as too much? (roof, install)

[Shakertime]

I have read several threads here on city data about roof vents but can't find an answer to this question.
I understand that there needs to be enough soffit venting to keep the air circulating properly in an attic. But is there such a thing as having too much soffit venting? I would think that if the roof vents had enough incoming air to push the hot air out, if there were more than enough soffit vents, they would just pull in a little less air than they were capable of. Does this sound right?

I've talked to many roofers and taken estimates, but boy, some don't seem to know much about venting.

[MrRational]

Originally Posted by Shakertime

But is there such a thing as having too much soffit venting?

There can be.

You want to BALANCE the volume of air in vs out...
and EQUALIZE the intake and exhaust along the length.

[need4speed2012]

Air Vent: FAQS

[Shakertime]

Thanks to both of your for input. According to that FAQ, you cannot have too much intake ventilation. They say that once pressurized, the excess vents will change to exhaust.

I hope this turns our right. I have had roofers come over to do the vents, but say nothing about more intake vents. They don't messure it out or anything. I had one guy tell me to put in the ridge vent, keep the gables open and not to uninstall the attic fan we have attached to one gable!! I know enough to know that's not right!!

[Roman45]

Here's a question to piggyback on this one. What if there is not enough soffit venting. I have turbines on the roof. These are new turbines and they spin almost continually with just a little wind. Using the mathematical equations I have found, we probably don't have enough soffit venting. How well are the turbines actually moving the air in the attic?

[K'ledgeBldr]

Originally Posted by Roman45

Here's a question to piggyback on this one. What if there is not enough soffit venting. I have turbines on the roof. These are new turbines and they spin almost continually with just a little wind. Using the mathematical equations I have found, we probably don't have enough soffit venting. How well are the turbines actually moving the air in the attic?

It basically depends on how fast they're turning-
A 12" diameter turbine vent with a constant wind of 5mph can move approx. 350cfms from the attic space. A single 14" diameter turbine vent that is subjected to 15 mph winds can expel up to 1300+cfm of air! If the winds are still, the vents still allow air to drift up and out of the attic space, although not nearly as much. So, prevailing winds will help a lot- if they're coming from the right direction. Otherwise, you have to consider the diameter of the hole(total sq/in) for the turbine as the vent for exhaust.