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-   -   Ridge Vent and Power Vent? (http://www.diychatroom.com/f9/ridge-vent-power-vent-82819/)

etern33 10-01-2010 07:04 PM

Ridge Vent and Power Vent?
 
I've read that different types of roof vents shouldn't be used in conjunction, as this may cause short-circuiting of air flow, but I haven't found a definitive answer. Should a Cobra ridge vent be installed if a power vent and a gable louver already exist? Or, must the power vent and gable louver be removed along with the roof louvers before a Cobra ridge vent is installed?

Gary in WA 10-05-2010 11:54 PM

http://www.ronhungarter.com/ventilation_repairs.html

http://www.ronhungarter.com/black_mold.html

Gary

handy man88 10-07-2010 05:41 PM

Quote:

Originally Posted by etern33 (Post 510041)
I've read that different types of roof vents shouldn't be used in conjunction, as this may cause short-circuiting of air flow, but I haven't found a definitive answer. Should a Cobra ridge vent be installed if a power vent and a gable louver already exist? Or, must the power vent and gable louver be removed along with the roof louvers before a Cobra ridge vent is installed?

Why do you think you need to add a ridge vent if you have a power vent and gable louvers already?

During the summer, the power vent will pull the heat out. Intake will come from your soffits, if you have them, and the gable louver. Heat will continue to exit via the power vent hole and the gable louver at nighttime when the fan will be off.

During the winter, the power vent will not turn on, so any heat will exit via your gable louvers, assuming you have soffits.

RoofDiagnostics 10-17-2010 04:45 PM

In my option this is an issue that often results in people making absolute statements when they are dealing with unique situations.

The above referenced link showing a mold ridden attic because of faulty ventilation installation is an example of this. While that situation is most likely 100% accurate - it does not mean that all homes with multiple sources of roof ventilation will result in condensation issues.

See, if you were in a vacuum conducting a scientific experiment a roof possessing a power attic fan and a cobra ridge vent - would most likely result in a decreased efficiency of ventilation. BUT - that is a vacum - your home is not a science experiment.

From my experience, i think the result of an attic fan and ridge vent is "competition" for air flow in a specific area. So in the area around the fan, the air might be pulled from two sources...but the area 25 ft across from the attic fan, i believe the cobra ridge vent is effective. The overall result in most of the homes with multiple sources of ventilation is a well ventilated attic/roof.

Of course there will always be scenarios where i am wrong but i know there are many cases where multiple sources of ventilation do not result in the air "short circuiting"


My recommendation: Install the Cobra Vent, pay attention to the attic area... if you believe you are experiencing "short circuiting" - get rid of the power vent.

Hope it goes well!

Ed the Roofer 10-18-2010 03:35 PM

I attempt to firstly use best practices and instructions per the ventilation manufacturers, along with the HVI, (Home Ventilation Institute), and seasoned with practical on hands experiences.

In your situation, I would advise following the manufacturers recommendations to NOT Short-Circuit the Exhaust Ventilation Flowage, so as to be in stricter accordance with their approved methods of installation practices.

But, at times I will allow for a considered alternative strategy that makes sense in a unique or particular situation if logic seems to follow with previous experiences.

Ed

rkpatt 06-04-2011 05:33 AM

My house has a hip roof. The roofer installed a ridge vent (relatively short since it is a hip roof) and left the power vent but told me to disable it (disconnect the wiring). The attic is hotter now . So, if I reconnect the wiring and use the power vent also , it will short circuit the flow if I don't stop the flow through the ridge vent ? Any suggestions on how to accomplish disabling of the ridge vent (short of removing it entirely) ? -Thanks

handy man88 06-04-2011 11:58 AM

Quote:

Originally Posted by rkpatt (Post 660813)
My house has a hip roof. The roofer installed a ridge vent (relatively short since it is a hip roof) and left the power vent but told me to disable it (disconnect the wiring). The attic is hotter now . So, if I reconnect the wiring and use the power vent also , it will short circuit the flow if I don't stop the flow through the ridge vent ? Any suggestions on how to accomplish disabling of the ridge vent (short of removing it entirely) ? -Thanks

Instead of disconnecting the wiring, you should have added an on/off switch and put it in the living space if possible, so that you can control the fan.

Given that, I would leave the fan on as "short circuiting the flow" is really overrated. If anything, the ridge vent will act like a soffit (intake) and add to the flow of the hot air out of the attic. Remember....warm air rises and as the temperature in the attic increases, so does the pressure.

If you insist on disabling the ridge vent, what you can do is use Tyvek tape and take the ridge slot from inside the attic to prevent air flow, but personally, I would not do it.

rkpatt 06-06-2011 07:06 AM

I got the power vent operating again (connected through a switch). The attic temperature measured with my min/max hygrometer/thermometer located 3 ft from the top of insulation /4ft from the peak was lowered about 8 degrees with the fan on (132degF fan off -
124degF fan on =8 deg F difference . The max outside temperature was 95degF ) .

That temperature ( 125 deg F ) seems excessive and I am think that I need to increase the flow . I believe that I need to add more intake vents as well as bigger power ventilator . Do to access problems (2 and 3 stories), it will be be difficult to add more soffit vents. I would have to add some passive "turtle" vents on the non-street sides of the house a few feet up from the lower edge of the roof . Any recommendations on installing these (spacing, layout, straddle rafters, etc) are appreciated.

ref-
http://www.gaf.com/Roofing/Residenti...f-Louvers.aspx



- Thanks


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