[nrbq999]

Having a new roof installed on my split level house in New Jersey. My question is with regards to venting. I now have a roof fan that runs by thermostat and I have gable vent openings, no eve/soffit vents, no ridge vent. Roof contractor wants to install ridge vent and leave the roof fan. I have lived in the house for 3 years and as far as I can tell did not experience any problems from ice damning. Should I leave the roof fan on and also have the ridge vent inslalled? I have read some where that they work against each other. Or should I have them remove the fan and go with the ridge vent?
Thanks

 

[Grumpy]

I will start my response by saying... Ventilation is a science.

If your contractor wants to install ridge vent and attic fan he is nuts, and does not understand the principals of attic ventilation. Mixing two ventilation systems, especially these two, will comopletely short circuit your ventilation system and cause more harm than good.

When your fan kicks on it will suck air from the path of least resistance, that is your ridge vent because it is the closest. This means you will only be ventilating a very small area of your roof. When your fan is off, it will become an intake for the ridge vent, and again you will only be ventilating a very small portion of your roof.

http://airvent.com/professional/whyVent/evaluate.shtml check out where it says common mistakes.

I don't know the shape and size of yoru roof so I can not comment on the best method of ventilating your roof. Like I started by saing roof ventilation is a science and literally every roof has diffeent ventilation needs. If you post a pic I can comment on which method is best. Posting some approximate measurements would be nice too.

 

[Grumpy]

Oh yeah BTW I am certified by Air vent. I sat in their classroom for 6 hours on day listening to engineers explain to me what to do and not to do... and I am glad for it.

 

[Specialist]

Grump is right. You NEED intake down low(preferrably soffit). A couple of mushroom vents installed 2' up the slope won't cut it. None of the systems you mentioned will work by themselves. The gable vents will provide a crossbreeze. They will not remove all of the moist, humid, hot air with out the intakes. The fan works great - but where will it pull its air from? Gable vents, ridge vents, and power vents - if your contractor wants to mix and match - get a different contractor. The ventilation is not just for ice damming, and not just for the hot summer. People do themselves a disservice when they cover the whirlybird turbines with trash bags. Don't take any advice from these people. Google "house ventilation" or some derivative thereof. :Thumbs:
-Bill

 

[nrbq999]

re: your responses

Thank You Mr. Grumpy and The Specialists for your responses. I have had 4 contractors look at my house and none of them seem to be as knowledgable as you two.

 

[Grumpy]

Too bad you're not in the Chicago area. try this site if your looking for professionals www.contractorhunt.com

 

[warpmine]

I've read lower eve ventilation is more important then ridge. I went through this last year with a customer and determined this after reading hours upon hours. Cross breeze from the soffit is a must. Open the soffits as much as possible. After you accomplist that, install ridge vent using the pre-molded plastic from Airvent or GAF or the aluminum units. Nylon rolled vent doesn't come close to cutting it in flow numbers. The others have a lip that creates a votex effect as air passes over it by aiding the evacuation of the attic/crawl space air. Moisture from the living area is a big concern in a closed up cavity via mold. Many products on the market now to address the problems of older houses. One more thing, it was recommended that we close up the gable vents after you finish the soffit and ridge vents. By doing this, you will help the overall performance by eliminating the "vacuum leaks" as it were forcing the air to accelerate through the new system. Attic in the summer is much cooler now as well. Tested it for curiosity.

 

[minnesotaroofin]

How do you vent soffit/eave when there is only a 4inch overhang 2x4 truss construction open rafters. with a gutter on the fasia board?

 

[Grumpy]

I would say that in a ridge vent system the soffit vents are equally as important as the ridge vent. It's not likley anyone with a brain will install soffit intakes with no exhaust of some kind. It is common to not be able to install soffit vents due to the architecture of the house.

The answer, when you can't install intake, is to install static vents like mushroom vents, and install 1 sq ft of ventilation for every 150 sq ft of attic floor space.

Never install a ridge vent without equal or greater intake. As far as the flow tests go, you will see that the GAF cobra scored pretty well for being a nylon roll with no engineering to aid the evacuation of the attic air. Yes the rigid plastic vents with the lip on the side do create the burnelli effect which creates great forces of suction.

As a specifier I find myself trying to match my product with the needs of my customer. Quite often I have to balance the quality with the value. This means when comparing the Cobra rolled vent is more than adequate for most situations.

 

[minnesotaroofin]

So what you are saying is that the ridge vent is not good Idea when the architecture of the house does not permit soffit vents? To be honest I am not a real big fan of the ridge vent 9 out of 10 houses i use the turtle vents. And i do cut them low if i am unable to vent the soffits at the eave as well as high. Ridgevent is the only way to go if ceilings are vaulted. I have seen the ridgevent plug up with cotten wood as well as seen bees nests and lady bugs here in MN. The plastic Snowcountry vent is the only ridgevent i use.

 

[AaronB.]

You can intake vent a house with no overhang behind the gutter through the fascia.

 

[minnesotaroofin]

house gas gutters

 

[minnesotaroofin]

how?

 

[warpmine]

I don't want to be an advertiser for this company but DCI Products have a line of venting that can be used at the bottom of the roof. Check them out at www.dciproducts.com

 

[minnesotaroofin]

Thanks for the link i will have to check into it. I am just wondering if it will provide enough ventilation.

 

[Grumpy]

I dislike fascia vents especially if gutters are to be used. Many many manufacturers have fascia vents and I don't use any of 'em. They replace the gutter flashing so invite ice and water infiltration IMO.

We've created our own fascia vent in the past. It's a pretty nice system bust costly and really only cost effective if the roof is being replaced at the same time. We basically build out the fascia board.

 

[minnesotaroofin]

Yea i have extended the fasia a few times myself it is not cheap. More often i just cut turtle vents low up 2 feet. I know its not ideal but it does help.

 

[minnesotaroofin]

Heres one that had a bad problem with Ice dams re insulated knee wall and cut vents low added ridge vent to ridge and dormers. Has'nt had any more problems with Ice http://minnesotaroofing.com/DSC00423.JPG

This lady had no problems to begin she only had 2 gable vents we added 3 turtle vents Needless to say she could not afford much more than i gave her.
http://minnesotaroofing.com/DSC00396.JPG

 

[jkdon]

So are trurtle vents ok with gable vents? and what do you guys mean by 2' up. Is that 2' from the ridge?


thanks

jkdon

 

[AaronB.]

Take 24 ga. Kynar 500 finished steel. Fabricate a way oversized drip edge. Accommodate cobra vent to fit. cut put top of fascia board 2". Install cobra nad wood blocking for nailers. Install drip edge. Gutter gets screwed through nailers. Ice cannot get in, lots o' ventilation, aesthetically pleasing, pretty cost effective.