Power vent and ridge vent?


#1

As a followup from my other post, a question about ventilation.

My house has a cathedral ceiling in one half of the house and an atticed celing in the other side.

My current roof has a ridge vent and one gable vent at the end of the attic side of the house…also, there is a power roof ventilator on that side of the house.

One contractor told me that the power vent is messing up vetilation and that he would take it out and cover up the hole, letting the ridge vent and soffit vents (perforated soffit) do the work…

The other guys all want to leave the power vent in.

Thoughts on this?


#2

Take out the power vent.


#3

So, can you clue me in a bit on the “whys” on this?

Out of the 5 guys we have had look at our place, only the first one said to pull it…

This is the same guy who did our neighbors house about 6 years ago…he took their fan out too…then, a year later, when they had their AC and furnace replaced, the HVAC compnay suggested stronly reinstalling a ventilated fan and they did…

My fan is on a thermostat…it only kicks on when it is really warm and sunny out…My theory is that if the ridgevent were working properly, it wouldnt kick on at all…or maybe not.

What is the real scoop on how this should work?


#4

roofing.com/forum/search.php?mode=results

Enter “roof ventilation” in the search area and you will find over 1300 entries.


#5

well ill tell ya shadango,
if ya live were it doesnt snow then you can put as many power vents in as you want.
but evidently, in cold climates, ventalation
has to work a certian way as to not create condensation build up in attic due to the drastic temp difference form inside to outside.

all i can tell ya is if you live in a cold climate,
ya better listen to these guys about ventlation and insulation, or it will be raining in your attic without rainin outside.

gweedo


#6

Out of 5 contractors, you have only one that understands the principles of ventilation.

Also, you stated that a portion of your roof was a cathedral/vaulted ceiling. Each individual space between every set of rafters, called rafter bays, need to be ventilated directly, which one or only several powered attic ventilators would not be capable of doing.

Ed


#7

Hey ETR…

The cathedral’ed section of the house doesnt have the ventilator…The whole roof has a rdige vent…I assume the cathedral’ed part is using the soffit vents…

The attic’ed part of the house (also ridge vented) has a gable vent and a roof ventilator.

During the winter, the fan doesnt run at all…so no problem there, unless you are saying I shouldnt have the gable vent either?

Now in the summer, the power vent does run at times.


#8

The PAV on the roof could potentially draw in air and exterior weather elements into the attic if it is running and drawing in the air through the path of least resistance, such as a nearby ridge vented section.

Ed


#9

Hello,
If the power fan is working, why remove it. It is helping with the air flow.

Since one section of your house has a vaulted ceiling, the air in this area is not moving around as much, the venting in other areas of the house are doing the extra work for this, as long as there is soffit venting, to allow intake of air, roof venting to assit with exhausting it you should be fine.

For an example: (to much venting? not on my roof!)

I have a one story ranch with a low to walkable roof pitch with attic space through out except, vaulted sun room, We have installed, continuous soffit venting, Cap over ridge venting, 3 thermostatic controlled Power fans, and box vents . I have two Ac/Unit systems.

Even with all this at times it still is hot in the attic but now is bearable. The air flows much better inside the house to all parts and rooms.

Pending on where you are, I would keep the venting.

N.Carolina (where is seldom snows but still gets cold ,and hot summers.)


#10

Hello Goddess
Did you ever stop and think about the principals of all the exhaust vents you have? Every piece of literature I have read clearly states no to short circut the system, In other words, Your power vents will pull air from the slosest source of intake, in your case would be the box vents, and ridge vent. Doesn’ it make sense to not have those other 2 exhaust, and let the fans pull air from the intake vents? It does seem to make more sense to me, but I would be curious to know if there have actually been any tests to show the airflow in all 3 scenarios and the affect on attic temps with the different systems.Any thoughts Ed?


#11

Air will be drawn in form the nearest available source. Simple physics apply here, no smoke tests needed.


#12

On one hand I get that…

On the other hand, lets assume for a second that is the case…my power fan will suck air from the ridge vent and gable vent then, causing a negative air pressure near the ridge vent…and creating a space for the warmer air in the attic to rise into

If hot air rises, wouldnt it make sens that the warm air towards the floor of the attic would therefore rise to the ridgevent area and along with it bring air in from the soffits and in trun get sucked out the power vent?


#13

Enough of this poppycock. You CAN NOT use a ridge vent with a power vent. It will pull air from the closest source just like tar said. Path of least resistance.

If you have any questions drop me an email and i will call you and answer all of them for you.

Drag70buickgs@att.net


#14

Agreed.

Power vent creates vortex effect choking house and restricting flow.

Take out the power vent…Gables and Ridge vents alone work great.

Or…powered gable vent(s) + ridge vent.


#15

In this case, I even think that our detractor, Dennis, who proclaims the fallacy of short-circuiting of an attic ventilation with a combination of Gable Vents and Ridge Vents, would probably agree that the addition of a PAV, (Powered Attic Vent), would obviously contribute to pulling air IN through the closest portals, which would be the closest section of Ridge Venting.

At this point, I do know of studies related to Gable Vents being an intake source for external inclement weather, but any engineers whom I have requested information from specifically relating to “Short-Circuiting” have not graced me with any scientific and unbiased studies relating to short-circuiting.

Ed


#16

shadango - If your power vent causes a negative pressure at the ridge vent? How would warm air travel to and thru the ridge vent?


#17

Maybe I am using the wrong terminology…what I mean is that if the power vent is sucking out air at the top of the roof, it is creating a low pressure area for the warmer air in the rest of the roof cavity to flow into…

Our roof lasted 23 years with the ridge vent, gable vent and power vent all at once on that side of the house.

We are replacing the shingles because the front side of the house, the shingles have worn…(the front sees the most wind and weather)…the back side of the house is actually like new compared to the front…and we need the skylights replaced…The shingles are not curled or torn up at all…we did lose a few pieces in a storm over the winter…

If ventilation was a issue in our setup, I would think that there would be a visible difference in the shingle on the attic’d side versus the cathedral ceiling side…???


#18

The issue of “short-circuting” would only occur if the ridge vent and power fan occupied the same venting area. If they are partitioned then you have nothing to worry about. Also keep in mind that you woould get some ventilation even with a ridge vent and power vent in the same area, you just would not be optimizing. Everyone here tries to show the absolute best situation to do the task at hand. There are always lesser choices.

Obviously you had venting of some sort before. Could it be improved? Probably.


#19

[quote=“shadango”]Maybe I am using the wrong terminology…what I mean is that if the power vent is sucking out air at the top of the roof, it is creating a low pressure area for the warmer air in the rest of the roof cavity to flow into…

Our roof lasted 23 years with the ridge vent, gable vent and power vent all at once on that side of the house.

We are replacing the shingles because the front side of the house, the shingles have worn…(the front sees the most wind and weather)…the back side of the house is actually like new compared to the front…and we need the skylights replaced…The shingles are not curled or torn up at all…we did lose a few pieces in a storm over the winter…

If ventilation was a issue in our setup, I would think that there would be a visible difference in the shingle on the attic’d side versus the cathedral ceiling side…???[/quote]

Do you still have the original power vent?
They tend to burn out before the roof has served its useful life.

It is your house, if you want power vents in it you can have them.
Ridge vents and soffit vents are the preferred method for good reasons.


#20

Ok, so I just craweled around in my attic so I could install a junction box for the electric skylights going in…going to run it off the line that is feeding the electric roof vent, which seems to be on a virtually otherwsie unused circuit…

I realized that my soffit vents are completely covered by insulation…20" or more of insulation…there is inulation between the joists and then another layer running perpendicular to those…

I started to try and clear one of them but then realized that since all of my soffit andfacia are coming off anyways, it might be easier to just cut that insulation out while that is happeing…

Am I on track here?

Or is it possible to sneak in baffles from the ground outside?

If not, and I have to go up and remove it from the attic, it will be a real PITA…the pitch of the roof is not real steep so its doing a belly crawl to get to it…or should I just man up and clear the vents thru the attic?