# How to properly vent hip roof



## JTK (May 28, 2008)

We had a hip roof put on site when we had a pre-engineered house built 12 years ago. The roofer hired by the contractor apparently had cut corners. Unfortunately we were too busy taking care of everything else with building the new house and did not know about the problems:

1. The singles were nailed directly onto the roof plywood. There was no underlaying roofing felt paper. The nails have rusted and there is black stain running from each nail hole on the plywood, when looking up at the roof from inside. There was also condensation on the plastic channels. I discovered these when I took the insulation out to put in the skylights. The attic is unfinished and we are working on finishing it now.

2. There is no venting on the triangular sides of the hip roof. There is only one ridge vent across the top ridge. The roof is rectangular looking down from the sky. All the channels on the triangular sides between the rafters (above the insulation) are venting to a dead end, the top ridge header if that is what you call it.

Advice needed:

Should ridge vents have also been put on the sloping sides by the original contractor? If not, what venting system should have been put in to properly vent the air from the soffit, over the channels, and out somewhere on the top part of the rafters?

JTK


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## Ed the Roofer (Jan 27, 2007)

I have some photos of a roof where we installed Hip Vents, which normally goes against some of the ventilation manufacturers recomendations, but this section of the home had a vaulted/cathedral ceiling in place also.

We also had to install the Smart Vent Fresh Air Intake Ventilation System along 100 % of the gutter eave edges, or else the hip venting would have been useless.

You MUST have 100 % continuous fresh air intake for ANY venting to work on your home, with the vaulted/cathedral ceilings. Also, if you use vented aluminum soffit panels, they must be clean and have a free path of unrestricted air to the exhaust vent systems in place.

Ed

Here is a copy/paste of the photos I mentioned.

Can you guess from the photos which ones have adequate ventilation and a cold roof or which ones allow the heat to remain in the attic, causing ice dam problem potential?

FRONTAL VIEW OF HOUSE WITH HIP AND RIDGE VENTS.


RIDGE VENT AFTER FRESH 6" SNOW FALL


HIP VENTS ON SAME HOME AFTER 6" SNOW FALL


FULL HOUSE VIEW OF RIDGE VENT AND HIP VENTS.
SEE HOW THERE IS NO SNOW AT THE EXHAUST AREAS?

THIS HOUSE ALSO HAD 100% EAVE INTAKE VENTILATION PROVIDED FOR BY THE SMART VENT FROM DCI PRODUCTS INC.
THE RIDGE VENT BRAND IS THE SHINGLE VENT II FROM AIR VENT CORP.

NEIGHBORS HOUSE.


OTHER NEIGHBORS HOUSE


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## JTK (May 28, 2008)

Thanks Ed the roofer.

After lookig at the Smart Vent website, I understand what they are now. Your pictures are also proofs of the proper ventilation. So the solution to venting my hip roof is to put on Shingle Vent II ridge vents on the sloped ridges. At a 45 deg angle, would rainwater get in? As for the Smart vent, it is a fail safe idea, but I think our oversized soffit vents (14" overhange) would suffice for now. I will keep the rafter insulation back to keep the soffit opening clear. As I talked about previously, there are channels (not sure what they are properly called) running all the way up to the head rafter under the roof plywood. They maintain a 1" H x 12-14" W space above the insulation for air flow.

On my concern over the stained area around the roof nails, should I look at fixing anything before I have blue boards installed, for the cathedral ceiling? I think the moisture is from condensation inside rather than from water leaking in, as I actually saw condensation on the channels when I removed them to cut openings for the skylights. Coincidentally, the skylights are on the roof with the existing ridge vent. I wonder if the soffit/ridge vent are not doing their jobs due to restricted openings on both ends and hence reduced airflow?

JTK


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## Ed the Roofer (Jan 27, 2007)

I used a different Ridge Vent for the Hip Venting detail, since Air Vents, Shingle Vent II is not stated to be used on hips.

I used Vent Sure, from Owens Corning, which is a ridgid roll our vent that is warranted for venting hips on roofs.

Download a brochure from the Air Vent website, entitled, "Venting Hip Roofs" and on the last page of the brochure, it shows a method to ventilate the rafters below and above the Skylight that is installed in the path of air flow, which impedes the direct eave intake to roof top exhaust pathway.

Forget it. Here is the link:

http://www.airvent.com/pdf/literature/VentViews_HipRoofs.pdf

Ed


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## JTK (May 28, 2008)

Hi Ed:

Is the hip vent by Owen Corning you mentioned the VentSure Rigid Roll Ridge Vents with Weather PROtechtor Moisture Barrier? The product literature says it "is a shingle over, low profile ridge vent with Weather PROtector moisture barrier membrane. The internal membrane provides weather infiltration protection", and its "Unique design adjusts to almost any roof pitch (2/12 to 20/12)." Is this the one you used? Does the 2/12 pitch mean 2" rise per 12" run, a 15 degree angle? Is so, what is 20/12? My hip roof is somewhere between 35-45 deg, about 4.5 to 6" rise per 12" run.

JTK


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## johnk (May 1, 2007)

JTK said:


> Hi Ed:
> 
> Is the hip vent by Owen Corning you mentioned the VentSure Rigid Roll Ridge Vents with Weather PROtechtor Moisture Barrier? The product literature says it "is a shingle over, low profile ridge vent with Weather PROtector moisture barrier membrane. The internal membrane provides weather infiltration protection", and its "Unique design adjusts to almost any roof pitch (2/12 to 20/12)." Is this the one you used? Does the 2/12 pitch mean 2" rise per 12" run, a 15 degree angle? Is so, what is 20/12? My hip roof is somewhere between 35-45 deg, about 4.5 to 6" rise per 12" run.
> 
> JTK


A 20/12 pitch is the same 20"rise per 12" run


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## Ed the Roofer (Jan 27, 2007)

JTK said:


> Hi Ed:
> 
> Is the hip vent by Owen Corning you mentioned the VentSure Rigid Roll Ridge Vents with Weather PROtechtor Moisture Barrier?
> 
> ...


Yes,

I used The Owens Corning VentSure Rigid Roll Ridge Vent with the WeatherProtector Moisture Barrier for the Hip Vent Applications, installed per the manufacturers specific instructions.

A 35* sloped roof would be "About" an 8/12 pitch

A 45* sloped roof would be "Precisely" a 12/12 pitch

John answered your question correctly regarding the rise/run for the example of a 2/12 pitch.

Ed


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## JTK (May 28, 2008)

Thanks for your explanations. Somehow I had a mental block understanding the rise and run, and I took college calculus. Silly me.

JTK


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