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Old 10-16-2011, 06:10 PM   #1
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HOT attic!!


I currently have the blown in insulation in my attic. I installed a attic vent with a fan to try and draw out the hot air and it works ok i guess. In the summer months it get very hot in the upstairs rooms and I'm guessing it because of the attic being so hot. The house was built before it was required to have two ac units when you have two floors in your house. How can i remedy this problem. Not sure if i should add more insulation or what. Def not trying to add another unit bc i def don't have the money. Any ideas will be very helpful.

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Old 10-16-2011, 07:40 PM   #2
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You failed to tell us where you live---that would be some help---

Make sure that the soffits are well vented and that the rafters heading to the soffits are not blocked by insulation.

When you are in the attic without lights on--you should see light coming in around the perimeter at the soffits.

How much roof top vents?

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Old 10-16-2011, 08:33 PM   #3
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Attic fans are improper in most applications.

Blown in fiberglass is pretty much worthless as an insulator as well.

If your aren't sure if you have enough insulation...you can pretty much guarantee that you don't.
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Old 10-16-2011, 10:09 PM   #4
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every venting system must have an intake and an exhaust. The fan is the exhaust, but do you have any intake vents (soffit vents)? If you don't, the fan will never be effecient because it has no where to bring in cool air from
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Old 10-16-2011, 11:37 PM   #5
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every venting system must have an intake and an exhaust. The fan is the exhaust, but do you have any intake vents (soffit vents)? If you don't, the fan will never be effecient because it has no where to bring in cool air from
Yes it does...the house. That is why most attic fans are improperly converting the attic to conditioned space.

You are absolutely correct that exhaust without intake is not correct.

I suspect there is some sort of gable vent or similar.
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Old 10-17-2011, 04:01 PM   #6
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Dooggins1, welcome to the forum!

Again.... where are you located?

Gary
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Old 10-17-2011, 06:43 PM   #7
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Dooggins1, welcome to the forum!

Again.... where are you located?

Gary
Hey sorry j haven't had time to get here. I live in NC. Yes I do have sofet vents so it is pulling air through. I really just don't now what insulation is best to use if insulation is the answer.
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Old 10-17-2011, 10:57 PM   #8
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Is the HVAC ductwork in the attic? http://www.joelstiburek.com/topten/south.htm

Gary
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Old 10-18-2011, 12:30 AM   #9
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Is the HVAC ductwork in the attic? http://www.joelstiburek.com/topten/south.htm

Gary
thanks for the link. so unvented attics are better off than vented ones
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Old 10-18-2011, 08:34 AM   #10
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thanks for the link. so unvented attics are better off than vented ones
Depends totally on construction type and other factors.

Ventilated attics are a well proven design and when done properly, quite effective.

You can make a unvented attic just as inefficient as a vented attic if done wrong.
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Old 10-18-2011, 11:40 AM   #11
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thanks for the link. so unvented attics are better off than vented ones
In the case of southern buildings, they certainly can be. There are two real reasons why attics are vented.

1) Moisture control. By exchanging the air within the attic you can control the overall humidity (moisture) levels and promote drying. stagnant moisture within the attic leads to wood decay, reduced insulation effectiveness, and mildew possibilities.

2) Heat control. This isn't so much for the south, but for the north, and isn't so much for summer, but for winter. As in Gary's article, the heat reduction from the ventilation isn't great enough to make a case for definitive use in the south or north during summer. But in the north, the difference of a few degrees in the winter is the difference between having damaging ice dams and having no dams. The ventilation allows for the roof surface to remain cold enough that the snow doesn't melt when exterior temperatures are below freezing.
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Old 10-18-2011, 11:24 PM   #12
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So which type of blown-in insulation do you have and how deep is it?

Gary
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Old 10-18-2011, 11:30 PM   #13
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In the case of southern buildings, they certainly can be. There are two real reasons why attics are vented.

1) Moisture control. By exchanging the air within the attic you can control the overall humidity (moisture) levels and promote drying. stagnant moisture within the attic leads to wood decay, reduced insulation effectiveness, and mildew possibilities.

2) Heat control. This isn't so much for the south, but for the north, and isn't so much for summer, but for winter. As in Gary's article, the heat reduction from the ventilation isn't great enough to make a case for definitive use in the south or north during summer. But in the north, the difference of a few degrees in the winter is the difference between having damaging ice dams and having no dams. The ventilation allows for the roof surface to remain cold enough that the snow doesn't melt when exterior temperatures are below freezing.
thanks. yea that's kind of what i am gathering from all this reading. it's kind of funny but i feel like the more i read the more confused i get. its like theres always an argument against each theory/ design.

so i guess my concern is-in my case i am doing an unvented roof assembly with open cell foam underneath the decking. the attic is thus part of the conditioned space. so after foam and drywall, i am done right?
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Old 10-19-2011, 10:07 AM   #14
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thanks. yea that's kind of what i am gathering from all this reading. it's kind of funny but i feel like the more i read the more confused i get. its like theres always an argument against each theory/ design.

so i guess my concern is-in my case i am doing an unvented roof assembly with open cell foam underneath the decking. the attic is thus part of the conditioned space. so after foam and drywall, i am done right?
prime and paint the gwb for the class III vapor retarder i believe is required in your area.
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Old 10-19-2011, 06:21 PM   #15
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So which type of blown-in insulation do you have and how deep is it?

Gary
Not sure of the name but it is the white kind. It is about 8-10 inches deep.

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