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Old 07-10-2019, 08:01 PM   #1
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problems with attic ventilation


Wasnt quite sure which area to post this question in so if any mods see a problem, please feel free to move to the appropriate area. 😀

My 1250sqft house stays pretty warm so I finally figured out that it's a couple of problems in the attic area. 1 problem is that the insulation in the attic is almost nonexistent. I currently working on getting that fixed. The second problem is that the attic stays super hot. I put a digital hygrometer probe in the artic opening and left the display out where I could see it. The temp in the attic around 5 this afternoon was about 120⁰. It's an old house built in '72 so theres some spider webs up there and I noticed the dangling spider webs weren't moving at all meaning theres no draft from air getting pulled in the soffits and exiting the areas for exhaust. The house has 10 total soffits that measure about 10x6'. I can also see 3 areas that look like ventilation exhaust. I.e. the house has a gable vent, a dome type passive vent and appears to have a ridge vent as well. Its approximately 50⁰ hotter in my attic than my house. I thought about just adding a fan vent until I noticed all the supposed exhaust areas. My electric bill would greatly appreciate any insight on how I should proceed bc I'm clueless at the moment and not looking forward to a 400$ electric bill for this month. I'm located in middle/northern Alabama with Birmingham being the closest city you guys may know. I unscrewed on of the soffits earlier just to check if they were blocked and the one I checked wasnt but it didnt pull any air in with the smoke test. I'd greatly appreciate any help you guys could give getting to the bottom of this. TIA 😊
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Old 07-10-2019, 08:15 PM   #2
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Re: problems with attic ventilation


It's better if soffet air has access to every bay between rafters and you likely have insulation tucked down blocking what you have.

Before you do more insulation up there, you need to seal every hole from the house thru the ceiling. Holes around plumbing vent pipes, wires, exhaust vents, chimneys, anything else you can find.

You want air chutes at the eaves to allow air into the attic.
Having ridge and gable vents may be a problem but you can judge that after all the rest is Complete. . You always want more soffet vent sq in. than you have high sq. in.
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Old 07-10-2019, 08:27 PM   #3
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Lol when I said I was working on the insulation I included air sealing in the term. My fault for not clarifying. I've been dreading getting up there bc of the heat. The soffit I checked was clear. Was able to shine a flashlight in the hole and there was no insulation in sight. I'd like to try to get it a little cooler up there bc if I get up there to do the insulation I really dont want to catch heat stroke or pass out and fall through the ceiling.
Owen's Corning website states an even amount of sq in above and below and their calculator stated I needed 600sq in above and below. I think the below is covered but will need to stay up in the attic for a while to get measurements for the upper area. Did i mention you have to crawl everywhere in the attic? It takes longer to do everything up there bc of that. I really dont want to pass out up there bc I may not come out at 120+⁰.
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Old 07-10-2019, 08:59 PM   #4
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Re: problems with attic ventilation


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Originally Posted by blackjapanx View Post
Lol when I said I was working on the insulation I included air sealing in the term. My fault for not clarifying. I've been dreading getting up there bc of the heat. The soffit I checked was clear. Was able to shine a flashlight in the hole and there was no insulation in sight. I'd like to try to get it a little cooler up there bc if I get up there to do the insulation I really dont want to catch heat stroke or pass out and fall through the ceiling.
Owen's Corning website states an even amount of sq in above and below and their calculator stated I needed 600sq in above and below. I think the below is covered but will need to stay up in the attic for a while to get measurements for the upper area. Did i mention you have to crawl everywhere in the attic? It takes longer to do everything up there bc of that. I really dont want to pass out up there bc I may not come out at 120+⁰.
Some jobs are best planned in the summer and done in the fall.
In the meantime you could be working on more soffet venting.

An air chute gives you about 18"sq. of venting at each bay so you need a percentage more than that in holes thru the soffet.
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Old 07-10-2019, 09:35 PM   #5
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Re: problems with attic ventilation


Hi Blackjapanx, we can help you with the standard guidance which will increase the ventilation. However, passive ventilation isn't really intended to cool an attic.

You provided your location which helps (hot) now describe your house, specifically how high the attic is. Ventilation in an attic with a low slope roof will be poor. Run a tape measure up through the access and estimate how high the ridge vent is above the tops of the ceiling joists.

Rough estimate on your current soffit vents is less than half of what you need.
The 120 attic temp is actually modest. The reason that heat is a problem is the minimal insulation. As Neal said, lots of air sealing is needed before everything is buried in more insulation.

Your gable vents along with a ridge vent are good if they are working. Pictures from the outside of the gable vents and the ridge vent will help.

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Old 07-10-2019, 10:10 PM   #6
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Re: problems with attic ventilation


I have about 25 soffit vents on my upper level (tri-level home) and 22 on the lower level. If I were in your shoes I'd concentrate on adding at least twice as many soffit vents as you currently have and making sure that the ones you have are not blocked. Once the weather cools off then I'd do as everyone else suggests and work on air sealing / insulation and maybe adding roof venting.

The temperature probe is a good idea, but you should be comparing the reading to outside air, not the conditioned air in the house. I also have a remote temp probe in the attic, permanently mounted, and it is usually around 10 degrees warmer than the outside air, unless the sun is beating down, in which case it may be a few degrees higher.

I've been in my attic in the summer many years ago. I don't think I'd venture up there if the temps were 120 degrees in the attic. Like Nealtw mentioned, it might be best left till the fall.
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Old 07-11-2019, 07:18 AM   #7
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Re: problems with attic ventilation


Are your soffit vents actually clear? Can you see daylight from them when you're in the attic?

ITA with Neal about waiting til fall to do the work!
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Old 07-12-2019, 07:42 AM   #8
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Re: problems with attic ventilation


Maybe you should wait til oct or nov. There is no way to cool it even with an attic fan. Unused attic is supposed to stay as such. For laboring like yours, you'd want below 90 deg F because there isn't even little breeze to help. Good planning and frequent rests with water or maybe even a shower to cool down. Some sort of walkway. Don't work on the joists in that kind of heat.
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