Roof Ventilation


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Old 12-04-22, 05:01 AM
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Roof Ventilation

I have a 20+ yo vinyl sided house in west Georgia. Nat. gas heating system with the furnace/air handler in the attic. Full ventilated soffit around the perimeter with a gable style roof. There are wall vents at each gable end of the house just under the peak.

My house has always been comfortable in the Winter. This year, not so much. Its been cold somewhat in NOV this year and the interior feels chiily and drafty. The heat seems to run a bit more than last year. At the prices we're paying for fuel this year, I don't need that especially going into the dead of winter.

So looking at what has changed this year vs. last. I had a new roof put on the house in July with the Cobra peak ventilation system. That is standard for roof replacement with GAF shingles in this area apparently. My sister had a similar roof put on her house, similar size and construction, a couple years ago and her house is not drafty like mine. The one difference I see between our houses is hers does not have the gable end vents on the side walls.

Is my roof now "over ventilated" causing it to be drafty? If so, how do I correct it?

Thanks in advance for any help.

 
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Old 12-08-22, 07:34 AM
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Not a roofer but it was always my understanding if you both gable and ridge vents the ridge vent can pull in moist air thru the gable vents. I always thought when you added ridge vents the back side of the gable vents was covered.
 
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Old 12-04-22, 05:15 AM
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With the exception of those who believe more ventilation is better, when continuois ridge vent is installed, its usually recommended that gable vents be closed off. But other than that, next thing you would look at is whether the attic floor is adequately insulated. Generally R49-R60 is recommended for your area. (See https://www.energy.gov/energysaver/insulation) Because if simply changing the roof and roof ventilation has made a big difference, my first thought is that your attic is not well insulated.

And energy prices are definitely higher this year, especially natural gas. So even if all things were the same, you'd still be seeing higher prices this year than last.
 
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Old 12-04-22, 07:42 AM
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Ventilation is a balance, between the incoming and outgoing but even with that right or wrong it should not effect the condition space. Possibly the exception would be with a lack of air sealing.

https://www.gaf.com/en-us/for-profes...ion-calculator

As noted R30 is pretty low these days and if you look at the differences between cellulose and fiberglass the cellulose is better for air sealing and overall performance.
 
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Old 12-04-22, 08:58 PM
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Yes, and the inspector should look to see if your chutes are high enough for the additional insulation and that insulation hasn't blown around... or created any thin areas. The problem with too much ventilation is that you will get wind gusts that blow insulation away from the perimeter... or blow it from one side to the other and plug up the ventilation on the leeward side of the house.
 
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Old 12-06-22, 04:49 AM
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I'm reading this with interest. I have gable end vents, soffit venting, and had my roof replaced several years ago, with continuous ridge venting. I haven't had any issues, but I never heard anything about removing the gable end vents to prevent "over-venting". hmmm-

Steve
 
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Old 12-08-22, 08:23 AM
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Thorough article on ridge vents and/or gable vents.
https://roofcritics.com/ridge-vent-vs-gable-vent/
 
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Old 12-04-22, 05:22 AM
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I have R30 rated blown in fiberglass insulation in the attic now that the builder does on all these houses. It could probably use more. The walls are supposed to be R13 plus sheathing. I have vaulted ceilings in the MBR and master bath, they're R19.
 
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Old 12-04-22, 07:13 PM
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I guess in my case they would just blow in more fiberglass? I've got someone coming out to do an assessment.
 
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Old 12-08-22, 06:02 AM
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Steve, I have the same question. My new roof came with continuous ridge vents whereas the old roof did not have them. I have full length soffit venting on the east and west face of my house and the gable end vents on the north and south face. Am I over ventilating my attic in the winter causing a drafty house and higher energy bills? The house was fine for 20 prior winters with the old roof. Should I cover the gable end vents at least for the furnace months? I'm in west Georgia.
 
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Old 12-14-22, 06:39 PM
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Thanks for the responses. My research led me to the same conclusion so I've started working on covers for both my north and south gable vents. I've got the south end 99% blocked now and the north is still open, will install the covers I made today tomorrow.

Already, I can feel the difference inside the house. The draft is gone which really made it uncomfortable on the coldest days we've had already this fall. We're forecast for 30's after tonight and even 20's leading up to Christmas. So I'll be able to compare for sure by then.

On another note, I can attest to the difference in my nat. gas bill by setting the thermostat to slightly cooler temps. I kept the house at 70 degrees night and day last year due to medical reasons. This year it was 66 day and set back to 62 overnight. Even with the attic ventilation working against me, I used 40 therms this last billing period compared to 72 therms for the same exact period last year. With energy costs up this year, this should help me not have too big an increase in my bills if any at all.

Thanks again for the advice. I'll post later after I see how the vents work out longer term.
 
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Old 12-27-22, 04:27 PM
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Got the north and south end gable vents covered and decided last THURS to cover the west facing gable vent I didn't even realize I had when I started this project. Finished this vent job THURS evening as the temp was dropping with the Arctic blast we had come through. FRI AM was a low of 16 and SAT AM it bottomed out here at 8. Covering these vents made a HUGE difference in keeping my house out of the deep freeze.

Next, I think I will work on sealing up the ceiling outlets(lights, fans, etc.) and look at blowing in some additional insulation before next winter. The builder blew in some at time of construction but that was marginal(R30 claimed) and its been settling for over 20 yrs. I'll look at increasing it to R49.

Pondering what to do about my garage. I have a 20x22 foot garage, currently no insulation in ceiling and don't think the walls have any either. Metal uninsulated door. My hot water heater(gas fired) and water supply lines are out there on the back wall next to kitchen wall. The temp went as low as 31 degrees out there during the coldest time and I ran a small utility heater I had some during the coldest time which was effective in boosting the temperature a few degrees above freezing. Never lost power thankfully like some in my county.

Any suggestions on heating that space? I would like to be able to do work out there during the winter. If I could maintain 60 out there on the coldest days, I think that would be enough?
 
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Old 12-27-22, 04:54 PM
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Since you've got gas out there you might look at putting up a small ceiling mounted unit.

I don't think I'd worry about insulation if it's just going to be occasional use here and there. Because you have a lot of space to insulate and you'd probably want new insulated doors too.

If you want to just do something temporary to the doors just glue some rigid foam to the garage doors with some spray foam. You can usually use some thin plywood braces across the foam to keep it held tight to the door until it cures. It's better than nothing. Measure what thickness would work best with your door.

If you are wanting to keep the garage 50 or 60F constantly, that's a different story. Then you'd want to insulate everything for sure. A company that blows cellulose could come drill holes and do that no problem, assuming your walls are finished.
 
 

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