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-   -   vents for a hip roof (http://www.diychatroom.com/f9/vents-hip-roof-100856/)

ratherbefishing 04-07-2011 11:10 PM

vents for a hip roof
 
I am adding a small addition to my house. Framing's done, so it's time for a roof. It's been 20 years since this one was installed.

I'm in Atlanta, so snow isn't really a concern. 100 degree days are.

The single story house is approx 1000 sq ft, plus the 80sq ft addition. Overhang/soffits are about 23 inches deep. The main house has a hip roof, 2.5 in 12. The adddition is the same pitch, but has a gable end. Rise at the ridge of the addition is only about 2 feet or so. About 3.5 feet in the main house.

I've never been satisfied with the venting. Soffit vents, plus 3 or 4 turtle backs. Blown in cellulose for insulation. The holes cut under the turtle backs are tiny. They could be tripled in size. A ridge vent would only be 20 or so feet long. I've read (online) good things about dormer vents, but am unsure if they'll work on such a flat roof.

What do you think?

BigJim 04-08-2011 11:00 AM

I would go with the dormer vent and with all vents I could get including the ridge vent and hope they would all do the job, every little bit helps.

Clutchcargo 04-08-2011 11:38 AM

You could use a power vent. It's probably the most effective way to vent the attic space with such a shallow pitch.

seeyou 04-08-2011 02:07 PM

1 Attachment(s)
OK, 1st, I build and sell dormer vents. A lot of them. The problem with using them on a low pitch roof like yours, is the steeper the pitch is the smaller they (and less expensive) they are. See the attached drawing.

On a 12/12 roof, a 2' tall dormer vent would be 2' long. The same face size would be over 9' long on a 2.5/12.

There are other types of vents available beside the standard type "turtle" vents that are more decorative and have much more free air space. Some sort of custom dormer vent that tapers back toward the roof might also be an option. I've never had this question come up before and I've got some ideas, but I'd have to sketch a little to figure out how to make it work.

The power fan idea has some merit, but only if the attic has been air sealed. Otherwise, it can cool the attic down by pulling conditioned air from inside. Probably not the effect you're going for.

ratherbefishing 04-08-2011 02:35 PM

Thanks for the advice so far. I've been doing a little research myself, and found this site. http://roofvents.com. A good phone conversation yielded a recommendation of a few of these: http://roofvents.com/roof-vent.html, combined with enough soffit vents.

I'm thinking about their bathroom fans, too. http://www.roofvents.com/bath-fan.html

Am I heading in the right direction?

ratherbefishing 04-12-2011 08:24 AM

I've been doing my research, and am still a bit confused. None of the ridge vent manufacturers I've called (GAF/Cobra and Shingle Vent) recommend their products for a 2.5/12 roof. The turtlebacks I have up there now don't leak, but don't vent much either. The folks at roofvents.com recommend their Aura Vent on a 6" riser for my application. But I can't find much more info on the Aura Vent. All the local roofers I've spoken to recommend the products they've used before, regardless of the pitch.

It's time to put on some shingles. Help!

seeyou 04-12-2011 08:34 AM

You say the roof is gabled. Can you add a gable vent?

I'd go with what you know works. Re-cut the turtle vent holes and maybe add more of the same model.

ratherbefishing 04-12-2011 09:04 AM

Seeyou,
The main house has a hip roof. The addition is very small (6x13) and has a gable, but the air space above the addition is not connected to the main roof. The ridge on the addition is quite long, as you drew in your diagram, so there's plenty of ridge and roof to vent a 80 sq ft space. Are the turtle vents effective, if installed correctly? I realize that the holes cut under them are too small, but is proper installation and a couple more a good solution?

They sure are cheaper than the Aura Vent. But I have an opportunity to do it right, and would like to solve the problem.

seeyou 04-12-2011 09:15 AM

Quote:

Originally Posted by ratherbefishing (Post 627842)
Seeyou,
The main house has a hip roof. The addition is very small (6x13) and has a gable, but the air space above the addition is not connected to the main roof. The ridge on the addition is quite long, as you drew in your diagram, so there's plenty of ridge and roof to vent a 80 sq ft space. Are the turtle vents effective, if installed correctly? I realize that the holes cut under them are too small, but is proper installation and a couple more a good solution?

They sure are cheaper than the Aura Vent. But I have an opportunity to do it right, and would like to solve the problem.

Yes and yes. Never used the Auravent, so I can't comment on it. Gable vent, ridge vent, turtle vents are all fine if installed properly. Since you can't use the 1st two, it looks like turtles are in your future. But make sure to use plenty. The minimum venting you should have is 1/150 of your attic square footage equally divided between intake and exhaust. More is better.

ratherbefishing 04-12-2011 09:37 AM

Thanks, Seeyou.


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