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Old 07-25-2012, 01:13 AM   #1
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Thinking of installing ridge vents...


Hello all.

First time on this forum. Came across it while searching for info about ridge vents, and have already learned alot form the members on here.

The temp in my attic at the highest point was 111F, and 99F at the floor of the attic. Temp inside the house was set at 80F. I have been thinking about having ridge vents installed, to try and keep the attic cooler as well as maybe save some money on my power bill. Ridge vents seemed to be a good way to accomplish that.

A roofing company came to give me an estimate today. They measured ~200 lineal feet of soffit vent, which they said would provide about 1200 sq inches of Net Free Vent Area for intake ventilation. They estimated my attic area as ~2600 sq ft. They are planning on using Owens Corning VentSure 4-foot Strip Ridge Vents with 20 sq inch/ft NFA. They are planning on installig 30' of ridge vent, which they say is the maximum they can install on my roof, according to a chart in the VentSure brochure. Installation will cost $750 total. They said the pitch of my roof was 4-5.

I have 8 square roof vents already in place. Do I need to have these sealed or capped ro can I leave them in place as they are, and expect them to help ventilate the attic when the ridge vents are in place? If they need to be sealed/capped, can this be done by simply laying some board across the opening from inside the attic?

Does the estimate and information provided by the roofing company sound accurate? The person did not seem to be very knowledgeable about the dynamics of airflow in an attic, and essentially read me the info straight from the brochure. I tried to search for info about VentSure ridge vents, but did not find much on the forum.

I know these may be very basic questions, but I would appreciate any recommendations from other members. Thanks in advance.

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Old 07-25-2012, 06:59 AM   #2
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Thinking of installing ridge vents...


What do you mean by "8 square roof vents", are these soffit vents? If so, you want to keep those. Air comes in through the soffitt vents and out the ridge vent. I'd be leery of a roofing company that didn't know everything about airflow. I'd get one or two more estimates. Call back the roofer and ask them, they should know.

Common sense tells me that mixing exhaust vents would be a bad thing. When we had our ridge vent installed, we closed off the gable vents and added more soffit vents. You wouldn't want your roof louvers becoming intake vents. I'm not a roofing professional though, hopefully someone else will chime in here.


Last edited by Pianolady; 07-25-2012 at 09:00 AM. Reason: add more info
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Old 07-25-2012, 07:52 AM   #3
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Thinking of installing ridge vents...


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What do you mean by "8 square roof vents", are these soffitt vents? If so, you want to keep those. Air comes in through the soffitt vents and out the ridge vent. I'd be leery of a roofing company that didn't know everything about airflow. I'd get one or two more estimates.
Roof Louvers

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calikingTX (07-29-2012)
Old 07-25-2012, 02:59 PM   #4
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Thinking of installing ridge vents...


Yes, I have the roof louvers already in place.

I am also concerned about the existing roof louvers acting as intakes and in effect "short-circuiting" my plan for attic ventilation. From the VentSure brochure (http://roofing.owenscorning.com/docs...sure-strip.pdf), page 3 has the numbers for Net Free Vent Area, etc. For installing ~30' of ridge vent, the minimum required soffit vent area is 620 sq inches of NFVA. The roofing company measured 200 lineal feet of soffit vent already in place, which they estimated to be about 1200 sq inches.

From what I understand the NFA of the ridge vents should be equal to or less than the NFVA of the soffit vents, correct? Given that the 30' of ridge vent is equal to ~620 sq inches NFVA, should I leave the roof louvers as they are, or should they definitely be sealed? Estimating that the existing roof louvers are 9" x 10" and the NFVA is 60 sq inches per vent, they provide about 480 sq in NFVA. If i have 1200 sq in NFVA from the soffit vents as intakes, would leaving the roof louvers open and adding ridge vents be ok?

I am going to try and get estimates from a couple of other companies. If anyone has any recommendations for contractors in the Houston area, please let me know
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Old 07-27-2012, 09:33 PM   #5
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Thinking of installing ridge vents...


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Yes, I have the roof louvers already in place.

I am also concerned about the existing roof louvers acting as intakes and in effect "short-circuiting" my plan for attic ventilation. From the VentSure brochure (http://roofing.owenscorning.com/docs...sure-strip.pdf), page 3 has the numbers for Net Free Vent Area, etc. For installing ~30' of ridge vent, the minimum required soffit vent area is 620 sq inches of NFVA. The roofing company measured 200 lineal feet of soffit vent already in place, which they estimated to be about 1200 sq inches.

From what I understand the NFA of the ridge vents should be equal to or less than the NFVA of the soffit vents, correct? Given that the 30' of ridge vent is equal to ~620 sq inches NFVA, should I leave the roof louvers as they are, or should they definitely be sealed? Estimating that the existing roof louvers are 9" x 10" and the NFVA is 60 sq inches per vent, they provide about 480 sq in NFVA. If i have 1200 sq in NFVA from the soffit vents as intakes, would leaving the roof louvers open and adding ridge vents be ok?

I am going to try and get estimates from a couple of other companies. If anyone has any recommendations for contractors in the Houston area, please let me know
from what i been told, installing mixed vents is a bad idea because like you said they will become intake vents also make sure your vents are installed closely to your ridge vent or they will short circuit no doubt about it meaning all vents up by the peak and not have some at the peak and some in the middle of your roof, for it to work properly they should be patched or use one or the other, another tip you shouldn't have any roof vents parallel to each other for example one on one side of your peak well there is another directly across from it on the other side of the peak

Last edited by vandel777; 07-27-2012 at 09:47 PM.
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Old 07-27-2012, 10:56 PM   #6
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Thinking of installing ridge vents...


I am a big fan of attic ventilation. It is very important for overall attic health. Your ventilation is already pretty good. If your idea here is to save money on your electricity bill I would make sure first you don't have somewhere else you can spend this money.

Your intake is great. For intake, you can't have too much. In a 4-5 sloped attic, insulation can be pushed easily over the soffit and block the air flow. Do you have some kind of baffles in each bay preventing insulation from blocking the air flow? With the baffles in place you want the insulation extending over the top plate, (exterior walls), as thick as possible.

Your existing exhaust ventilation is light and it wouldn't hurt to add a couple of more static vents. With all the intake you have, short circuiting won't be a problem if you really wanted to add the ridge vent. A proper answer would also be dependent on the complexity of your roof. You have a big attic and we are only talking about 30 feet of ridge. Also are your AC ducts running through your attic.

Also in Houston, TX, outside temp 99-100 last couple of days and the highest temp in your attic has been 111. That sounds pretty good. Ideally your attic temp would be with 10 degrees of outside temp.

I can't help but wonder if there would be someone else better to spend $750 to help save you on your electricity.
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Old 07-28-2012, 05:07 PM   #7
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Thinking of installing ridge vents...


Ah, Houston..... http://www.buildingscience.com/docum...uth-assemblies

Did you already air seal the attic and crawl space? http://www.jlconline.com/cgi-local/v...170a32100a05c7

Did you air seal the HVAC ducts and attic access? http://www.buildingscience.com/docum...sealing-guide/

http://www.joelstiburek.com/topten/south.htm

Gary
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Old 07-29-2012, 06:36 PM   #8
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Thinking of installing ridge vents...


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from what i been told, installing mixed vents is a bad idea because like you said they will become intake vents also make sure your vents are installed closely to your ridge vent or they will short circuit no doubt about it meaning all vents up by the peak and not have some at the peak and some in the middle of your roof, for it to work properly they should be patched or use one or the other, another tip you shouldn't have any roof vents parallel to each other for example one on one side of your peak well there is another directly across from it on the other side of the peak
Thanks for that tip. The current square roof louvers look like they are installed in the middle of the roof, not close to the ridge. If I go ahead with ridge vents, I am leaning towards having the roof louvers capped and sealed from the inside.
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Old 07-29-2012, 06:48 PM   #9
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Thinking of installing ridge vents...


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I am a big fan of attic ventilation. It is very important for overall attic health. Your ventilation is already pretty good. If your idea here is to save money on your electricity bill I would make sure first you don't have somewhere else you can spend this money.

Your intake is great. For intake, you can't have too much. In a 4-5 sloped attic, insulation can be pushed easily over the soffit and block the air flow. Do you have some kind of baffles in each bay preventing insulation from blocking the air flow? With the baffles in place you want the insulation extending over the top plate, (exterior walls), as thick as possible.

Your existing exhaust ventilation is light and it wouldn't hurt to add a couple of more static vents. With all the intake you have, short circuiting won't be a problem if you really wanted to add the ridge vent. A proper answer would also be dependent on the complexity of your roof. You have a big attic and we are only talking about 30 feet of ridge. Also are your AC ducts running through your attic.

Also in Houston, TX, outside temp 99-100 last couple of days and the highest temp in your attic has been 111. That sounds pretty good. Ideally your attic temp would be with 10 degrees of outside temp.

I can't help but wonder if there would be someone else better to spend $750 to help save you on your electricity.
I would prefer to take the path of least expense, but at the same time I want to take good care of my house. I'm no expert when it comes to roofing and ventilation matters, so I really appreciate the advice and info folks have given so far.

Today, when the outside temp was about 100F, the temp in the attic was 122F at the highest point. I measured 110F on the inside portion of a square static vent in the middle of the roof. However that section of the attic has the 2 water heaters for the house in it, so I wonder if that adds to the temp. And yes, I do have ducts running through the attic.

I don't know how much or how well the attic insulation was installed. I wouldn't be surprised if it was on the lighter side - I will have to look into that.

If it doesn't sound like ridge vents would add much, then I'm okay with not installing them. The money is not burning a hole in my pocket so I would love to hold on to it! From the Owens Corning pamphlet, 40 lineal feet of ridge vent is equivalent to 16 static vents, so the 30 proposed by the roofer would maybe provide the equivalent of 12 static vents (is that safe to assume?) I currently have 8 static vents/roof louvers in place, so would the ridge vents be equivalent to adding 50% more ventilation than what I currently have? I know I may have oversimplified this, but I'm just trying to understand if I will gain anything by going forward with this project.

Thanks again to all who have helped.
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Old 07-29-2012, 07:23 PM   #10
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Thanks for the articles. They made for very educational reading, especially the last one. I think I am convinced now that I was looking to install ridge vents for the wrong reasons, and that maybe I should leave things as they are. Saves me a bit of money - which I am absolutely okay with
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Old 07-29-2012, 11:02 PM   #11
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Thinking of installing ridge vents...


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Originally Posted by calikingTX View Post
Thanks for the articles. They made for very educational reading, especially the last one. I think I am convinced now that I was looking to install ridge vents for the wrong reasons, and that maybe I should leave things as they are. Saves me a bit of money - which I am absolutely okay with
if you leave the roof as is with your roof vents in the middle of your roof the top towards your peak is going to have dead air and any vents you have towards the peak wont be doing there job if they stay that way, they will just be sitting unused units causing the top half of your roof to lose YEARS! i repeat YEARS! on your roof, its clear what you should do here #1 remove all middle vents and have them install all by the peaks (most people like to have them installed on the back of the house) or #2 have ridge vent installed which is a more effective way to ventilate your roof its a continuous strip of ventilation
all the work is going to be done by your soffit vents and those middle vents if you leave it as in
please take this advise as it is the truth
this can be a "Do it yourself job" shouldnt take you to long. do a little research or asking a round for tips how to go about this if your willing to give it a go, the roof pitch is only 4-5/12 which isn't steep and pretty safe in my opinion (wipe of the bottom of your shoes)

Things you will need
Saw (cut 3-4 inches out in peak, or remove small board if there is one at peak, 1 1/2 - 2 inches each side of peak) (3inches is plenty )
Hammer
Nails (1- 1 1/4 nails , rollvent comes with longer nails)
Rollvent (peak)
Boards/Plywood (vent holes)
Hook blade for knife (cutting 3 tab shingle for peak (CAP) , cutting shingles to fill in your vent holes)
crowbar/roofing ripper (rip old shingles off, be careful when you breaking the seals so you dont damage them, you dont want to replace more shingles then you have to, (note to remove a shingle you simply break the seal of the shingle you want to remove and the shingle above it then remove the nails in both shingles you broke the seals of, if needs to be cut simply cut it in the KEY if 3 tab shingles, if laminated cut 6-8 inches back from the seam
Tape (filling holes, center rollvent

(probably left out some info because im tired and heading to bed now stop writting ha ill report back tomorrow to reread and see what i can add


Last edited by vandel777; 07-29-2012 at 11:21 PM.
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