Home>Discussions>EXTERIORS>Roofing Ventilation with no Overhangs. Need Advice!
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isomian
Roofing Ventilation with no Overhangs. Need Advice!
isomian

Hello!

I am in the market for a new roof because our current roof has hit its lifespan. I'll try to be concise without leaving off too much information.

My Situation:

Currently, we have an attic fan and 3 gable vents. There are no roof overhangs for soffit vents. By the way, our attic is unfinished and is a large open space. I would like a passive ventilation system using ridge vents for exhaust, however I have had 4 contractors suggest 4 different solutions:

Contractor 1: Use existing set-up for ventilation
Contractor 2: Use Vented Drip Edge for Intake Ventilation
Contractor 3: Use Smart Vents by DCI
Contractor 4: Use 2 Gable fans to create airflow through the attic space with ridge vent

I have researched each solution for air intake using ridge vents and each has its pros and cons.

My quandary: What is the best solution for ventilating an attic with no roof overhangs? I am open to suggestions and maybe ridge vents and a passive ventilation system is not the solution.

Thanks for your help!!

-Ian

llmotoll
Re: Roofing Ventilation with no Overhangs. Need Advice!
llmotoll

If the gable vents are freely passing air through them and are not blocked by storage containers, insulation or heavy foliage out side the home then they should suffice. Gable vents are the best in my opinion because they are not a roof component.
Should not have any other type of vents installed like a power roof vent, hat vents or anything else that may interfere with the gable vents.

Smart Vent by DCI is good. There are similar products out on the market. Installed properly will do the trick. But you will need to close off the gable vents so they function properly.

Another option would be to build an above deck ventilation. Essentially another roof deck above the existing so you have a 1" or more of air flowing from the eve to peek.

llmotoll
Re: Roofing Ventilation with no Overhangs. Need Advice!
llmotoll

You mentioned you have an attic fan. Not good, the opening in the roof will cause air flow problems with the gable vents. It will cause areas of the attic to be stagnate/hot spots/damp spots.
The air in the attic should be within 10 degrees+/- outside air temperature.

Any type of ventilation needs to be the only type of ventilation used on a building. When more than 1 type are implemented they will interfere with each other and by the time you realize there is a venting problem it's usually to late and the damage to the wood substrate/framing has already been done.

llmotoll
Re: Roofing Ventilation with no Overhangs. Need Advice!
llmotoll

BTW.... option #4 is retarded. Just saying.:)

isomian
Re: Roofing Ventilation with no Overhangs. Need Advice!
isomian

Thanks for your comments!

Ha! I don't like the sound of Contractor #4 either for numerous reasons. One being the consumption of electricity and I've never heard of anyone doing that before.

I am leaning towards using the Smart Vent style of intake ventilation. However, I have heard that their is a "reveal" that is noticeable. I have never seen this product installed on a house before. Have you ever installed or seen a roof that used a Smart Vent style of intake and was it that noticeable..?

Thanks

ed21
Re: Roofing Ventilation with no Overhangs. Need Advice!
ed21

I would use either the smart vent or vented drip edge.
I've specified vented drip edge on new construction that had rigid insulation on a sloped roof. I see potential problems on a retrofit if not installed properly. The insulation needs to be held back for proper air flow. More modification of the fascia and gutter may be required.
To me it looks like the smart vent is high enough on the roof to keep the air flowing properly over the insulation. Existing gutter and fascia should be okay.
Definitely passive ridge and soffit (or drip edge or smart) venting is the way to go. Even with gable fans and vented soffits my attic is much cooler with just a ridge vent that I had installed with a new roof.

llmotoll
Re: Roofing Ventilation with no Overhangs. Need Advice!
llmotoll

No, never installed a Smart Vent by DCI. The only issue you could have would be ice dam leaks. even if you have a self healing membrane underlayment along the edge, you will still have an opening in the deck about 12" up slope.

If you live in an area with snowy winters you may want to invest in heat cable for the edge to prevent ice dam leaks. The ice dam can also block any ventilation until it is melted.
Heat cable systems vary quite a bit from the type that simply plugs in - to copper line systems with automatic on/off thermostat controls.

isomian
Re: Roofing Ventilation with no Overhangs. Need Advice!
isomian
ed21 wrote:

I would use either the smart vent or vented drip edge.
I've specified vented drip edge on new construction that had rigid insulation on a sloped roof. I see potential problems on a retrofit if not installed properly. The insulation needs to be held back for proper air flow. More modification of the fascia and gutter may be required.
To me it looks like the smart vent is high enough on the roof to keep the air flowing properly over the insulation. Existing gutter and fascia should be okay.
Definitely passive ridge and soffit (or drip edge or smart) venting is the way to go. Even with gable fans and vented soffits my attic is much cooler with just a ridge vent that I had installed with a new roof.

Have you experienced any issues related to moisture entering the attic space using vented drip edge or Smart Vents? There is not an overhang, so it would be installed fairly close to the gutters. Also, we get ice/snow from time to time. Would the collection of snow and ice in the gutters block any intake airflow with either the vented drip edge or the the Smart Vent?

Thanks for your help? Maybe I am over thinking this too much...

llmotoll
Re: Roofing Ventilation with no Overhangs. Need Advice!
llmotoll

Regarding snow and ice blocking the vents. if you live in an area like Canada where they get snow and it stays all winter long until spring melt. yes ventilation would be a problem. But not if your region experience freeze thaw cycles during the winter months.

Water receding back through the vents will depend on volume of water run off and slope. If your slope is greater than 3/12 than no worries during rain weather events.

ed21
Re: Roofing Ventilation with no Overhangs. Need Advice!
ed21

I would think that the gutter should be as far below a vented drip edge as practical. A clogged or ice/snow filled gutter should not be able to backup unto the vent.
That's what I meant by possible gutter/fascia modification.
Don't forget baffles may be needed over the insulation for proper airflow.

Mastercarpentry
Re: Roofing Ventilation with no Overhangs. Need Advice!
Mastercarpentry

Just an observation here (and I know that you want a passive system) but the first question should always be "What kind of problems are you experiencing with the way things are now?" That leads to the old saying about not fixing what ain't broke. Sure, there are other ways to do it but if it's working fine now and always has, what is the point of adding expense through changes which for whatever reason might not work as well for you? That said I also like things that handle themselves without outside input or moving parts which will break down someday.

I'm a big fan of soffit and ridge vent systems when they are done correctly, and the vented drip-edge should handle the lack of soffits well enough. I don't like roof penetrations anywhere downslope because they have the potential to leak which doesn't exist if they are not there. Some are inevitable like plumbing vents and perhaps power feed conduits, but why make holes downslope for vents when they work best at the top? That roof is the most important part of protecting you and your investment from the weather so make it as reliable as possible. Eliminating penetrations is just one step in that process.

On ice dams etc I'll leave it to the other guys- my roofing experience and knowledge is from the south where we don't have those worries to fret over- wind and extremely heavy rains are what we fight down here, along with a summer sun that will bake any house with a poorly ventilated attic.

Phil

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