Ridge Vent vs. Power Attic Ventilator


#1

I have a hip roof with asphalt shingles on my house. The roof is 3 years old and I live in South Florida. They took down the whirly turbines and gave me a Cobra ridge vent. I also have 30 soffit vents that are screened 8" x 16" each. When it’s hot, I notice hot air flowing out from the soffit vents. In looking at the 20 feet of Cobra ridge vent, I am not too impressed with it’s ability to allow outflow of air. A neighbor suggested a power attic ventilator be mounted just below the ridge vent. I’m a little reluctant to cut a hole in the roof. I have also read that a power ventilator is not a good idea with central air conditioning which we use alot of the year here. And I read it’s not a good idea with a ridge vent. The house measures 47’ x 64" and it appears I have good intake NFA but not as good output NFA. Should I add the ventilator or consider upgrading the ridge vent? Nina


#2

If you have a hip roof then chances are that ridge vent is going to give you inadequate exhuast. Depends on the roof but hip roof ridges tend to be too short for ridge vent. I’ve never been a big fan of Cobra vent myself, stuff is like an african american toupee. We normally use Snow Country by GAF. In your case, without seeing pictures, I would go with a power ventilator. Which means tearing off the old ridge vent. Cutting the hole and installing the power vent is no big deal, 1 man can do it in an hour. Need an electrician too though. If you have hot air pushing out the soffit vent you have serious exhaust issues. Always a chance the roofers did not cut away the roofing materials before they installed the ridge vent too; I’ve seen that before.


#3

Little Red,

Where in South Florida are you? What town?

Here’s an idea:

  1. Go to maps.google.com & look up your house.
  2. Use the “satellite view” to see an aerial view of your house as close up as you can get.
  3. With your house centered on the image (you can L click, hold the button & scroll around to put the image where you want it, then release the button)… with the image centered, press “Print Screen” on your keyboard.
  4. Open MS Paint if you’re on a “non Mac” product.
  5. Press ctrl+v @ the same time; you just inserted the image from your Google map.
  6. L click & drag the image to the upper L so all we see is the house.
  7. Save the image as a .jpg (NOT a .bmp - too large) & insert it here on a message.

That may seem like a lot to do, but it will give us an aerial view of your ridge.

Back to the question if you don’t post an image here:

Ridge vent & a power fan will work in a tight circle where the fan sucks in from the nearest air source, i.e. the ridge vent.

Tar is right, though - some people make a mistake or are lazy & don’t cut out the slot on the ridge. Go into the attic during daylight hours & with the attic light off, look up. Do you see some sunlight coming through? If not, you need to have the slot opened & the contractor who did your most recent roof needs to take care of this.

You mention the Cobra ridge vent, but there are 3 types of Cobra products. The “Cobra”, “Cobra II” & “Cobra III” (I like the III & along with Tar think the original Cobra is junk). Tell us what it looks like if you’re up close to the ridge cap (or if it’s not too difficult for you, get a photo of the ridge vent from the side view, up close).

If you only have about 12’ or less of useable space on your ridge line, then it’s possible that a powered attic fan IS the way to go.

That means to remove the ridge cap & ridge vent, then put new shingles down on the ridge.

Next is to install the fan & here’s where I have a difference with Tar; use the GAF solar powered exhaust fan. 500 cubic feet per minute & no electrician required. The sun (or even some sun) is out & the fan is working for you. Even if it’s a cooler day, the sun will pull condensed air out of the attic space. I probably install about 20 to 30 of these a year.

The ony hard part is if you have a tight area @ the top of your hip roof; you may be competing for space with other pipes & bathroom fan components.

The other thing is to get the fan up high. If your street view is to the South, then use the remote solar cell option; there is a bundled up wire that you can untie & the fan comes with a foot mounting kit to take the solar patch off the fan & put on the South side while the fan can go up on the North (or back or wherever). This lets you run the wires through the attic.

You can also paint the fan the same color as your shingles; it’s always best to remove the solar cell before you do this (it’s held on with wingnuts, so this is a fast operation). I usually use the small cardboard solar part that comes in the box & keep it on the collector while I paint the fan that is about 1 ft. away - no sense in getting any overspray.

Hope this helps.


#4

I am in Boca Raton. I’m sure they cut the slit for the ridge vent. I have been up in the attic and on the roof and looked at it. It does look like a brillo pad. And it’s fastened tightly to the roof not really raised up much. Do I really have to seal off the ridge vent if I add the power ventilator? I can do the installation myself with my neighbors help who is an electrician. Or would replacing the ridge vent with a better model suffice? My house is a classic hip roof. I tried to get a copy but was unsuccessful. I did try to copy the url here. When you look at the picture. I don’t have that solar panel anymore or those whirly turbines you see in the picture.

maps.google.com/maps?f=q&hl=en&g … 7&t=h&z=20


#5

Yes, as I suspected your ridge is too short. No way you could put enough ridge vent (of any type) up there to adequately vent that roof. Yes, you should rip off the existing ridge vent and close it off with roofing materials. Yes, install a power ventilator. Good luck. Good call on the SAT photo, Ranch.


#6

Tar, I’ve started using Google Maps to look @ houses (as best as I can what with trees & older sattelite fly by’s) before I go out.

In some cases (like this house) I can actually do a roof sketch before I even go out & all I have to do is fill in the blanks on measurements.

I suggest a solar powered exhaust unit or two; you have a direct E / W ridge line, so the street view is to the South. Put the solar unit high on the N slope, there should be enough sun that high on the roof to collect OK. If not, you can also use the remote option as described /.

Little Red, back in '88 - '89, I used to clean pools in your area. Worked for a co. out of Deerfield Beach. If you ever go to a little Tex Mex joint on A1A in DFB across from The Whale’s Rib, Rattlesnake Jake’s, look for the large bald guy who owns it; tell Junior that Mark in Texas says “hi”.


#7

Thanks so much guys for your interest and advice. Now, any recommendations of a brand for the attic ventilator? I can get one thru Costco for $79.99 including shipping called Ventimatic Galvanized Roof Mounted with 1600 CFM and a 5 amp motor. It also has a thermostat. Is that one any good? It says I need 600 inches of intake which I have. But it’s only for a 2000 sq ft attic and mine’s bigger. I also wonder if it’s going to be loud with that 5 amp motor. Any quieter one’s? I know not to get one with a plastic cover because of the cracking it will do in the Florida heat. Anything else I should consider when buying one? And what else to avoid? Here’s a picture.

costco.com/Browse/Product.as … opnav=&s=1


#8

I am not familiar with that product.

http://www.homedepot.com/catalog/productImage/2071f561-ff3f-4841-8690-e2ca9d231368_300.jpg
If you insist on the hardwired version, then I suggest you use a name brand like the GAF MasterFlow @ 1,600 cfm’s.

$ 99.00 & it’s got their best warranty. I have no idea what an electrician will charge in your area, but a friend from high school is an electrical contractor in Davie & I could see what the going rate is for something like that.

If you DO want the hardwired version, I would suggest you get it installed NOW before the attic temps get too hot for someone to work up there.

http://www.homedepot.com/catalog/productImage/580fdf85-ed94-48ba-8d30-a6cfd2dbcaf8_300.jpg

This is the solar powered unit; they typically cost around 180.00 @ the Big Orange Box & my local supplier has a similar price point. For the solar unit & installation on a 'walkable' 4:12 to 6:12, I usually charge 400.00 to start, total.


#9

Thanks again. You guys have been so great about this. I’ve got an electric junction box already set up and available in the attic to run the motor so electric is my choice of a attic ventilator. The GAF MasterFlow is available for $99 at H.D. so I’ll get that. The question I have is can I seal off that ridge vent from inside the attic instead of on the roof. I don’t want to tear anything off outside if I can avoid it. Can I staple gun some felt (or plastic) over the ridge vent from inside the attic? Then when I get a reroof job, I should have them fill that ridge vent in? Nina


#10

Can I staple gun some felt (or plastic) over the ridge vent from inside the attic? Then when I get a reroof job, I should have them fill that ridge vent in? Nina

You could do that I guess. Not the best solution, but yes, the end result is to block the exhaust you currently have…which seems to be blocked anyways, lol.


#11

Blocking would be a cost effective, and a good short term remedy.


#12

I agree with the blocking option; get some of the reflective solar bubble wrap looking stuff & tack it to the underside of the ridge slot.

If you have any leftover product, go ahead & staple it to the underside of the deck & help out your heat island effect / energy signature. Can’t hurt… will last about as long as an exposed 15 # felt would…


#13

Sheeeesh, you guys are so…yesterday.

There is no good reason to block off the ridge vent. It will not interfere with the operation of the power vent. That source of air (the ridge vent) is restricted.

Furthermore, on a day when it is not hot enough to activate the power vent, the ridge vent will help to exhaust hot air from the attic along with the power vent.
roofersreview.com/PowerVentilators

roofersreview.com/ShortCircuitMyth


#14

A solar powered unit will operate no matter what the temperature is, provided there is even marginal sunlight, it will spin.


#15

:smiley:

Just curious ranch, what is the max cfm for that solar powered vent?


#16

I have stated before on this very thread & on lots others that the solar GAF unit moves up to 500 cfm’s(rated max, anyhow, which is possibly much like the bogus EPA mileage ratings for cars).