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-   -   HOT attic!! (http://www.diychatroom.com/f103/hot-attic-120317/)

Dooggins1 10-16-2011 06:10 PM

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.

oh'mike 10-16-2011 07:40 PM

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?

Windows on Wash 10-16-2011 08:33 PM

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.

bluebird5 10-16-2011 10:09 PM

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

Windows on Wash 10-16-2011 11:37 PM

Quote:

Originally Posted by bluebird5 (Post 750234)
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.

Gary in WA 10-17-2011 04:01 PM

Dooggins1, welcome to the forum!

Again.... where are you located?

Gary

Dooggins1 10-17-2011 06:43 PM

Quote:

Originally Posted by GBR in WA
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.

Gary in WA 10-17-2011 10:57 PM

Is the HVAC ductwork in the attic? http://www.joelstiburek.com/topten/south.htm

Gary

federer 10-18-2011 12:30 AM

Quote:

Originally Posted by GBR in WA (Post 751020)
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

Windows on Wash 10-18-2011 08:34 AM

Quote:

Originally Posted by federer (Post 751072)
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.

AGWhitehouse 10-18-2011 11:40 AM

Quote:

Originally Posted by federer (Post 751072)
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.

Gary in WA 10-18-2011 11:24 PM

So which type of blown-in insulation do you have and how deep is it?

Gary

federer 10-18-2011 11:30 PM

Quote:

Originally Posted by AGWhitehouse (Post 751311)
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?

AGWhitehouse 10-19-2011 10:07 AM

Quote:

Originally Posted by federer (Post 751820)
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.

Dooggins1 10-19-2011 06:21 PM

Quote:

Originally Posted by GBR in WA
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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