attic venting and insulation

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  #1  
Old 07-05-09, 04:53 PM
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attic venting and insulation

I need some input on attic venting and insulation.
The house has an attic but it has a 10' drop roof all the way across the front and back (low slope roof) The low slope roof has 2x6's rafters and has 6" fiberglass insulation in the entire area. The part of the attic that is accessible has blown in insulation on the roof floor. No ridge vent, only 2 small gable vent openings, and no soffit vents. The roof has singles on it, striped with 1x4 strips and metal roofing over that, so the only place that is venting a little is between the shingles and metal roof. The accessible part of the attic gets extremely hot in the summer and the heating and ac duct is located in this area. What would be an improvment to help with the heat? Close the gables vents up and remove the blown insulation on the roof floor and spray foam the acessible part of the attic rafters and make this a unvented attic? keep in mind the low slope is not accessible without tearing out the whole inside overhead ceiling, which is plywood and ceiling tex.

Has anyone come across something like this or got any suggestions.
 

Last edited by mlac52; 07-05-09 at 06:10 PM.
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  #2  
Old 07-06-09, 08:34 AM
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Is there a way to put in a fan that will help circulate the air?? You can buy a fan that mounts through your roof. I also have toyed w/ this idea. My attic gets super hot also and I have 2 gable vents and a ridge vent. A coworker of mine put a fan hooked up to a thermostat and as soon as it hits 90 degrees it kicks on. I think they put this in a gable vent. Not sure how you would control bugs. You could put screen over the inside part of the fan so they couldn't get in.

I have the same low sloped roof as you but only on the back part of the house. That had fiberglass on the ceiling of the
2nd floor. You don't have any insulation in the rafters of your roofs do you??

So I guess my non professional opinion would be a roof or gable fan, or a ridge vent? Not sure if the ridge vent is do able or even worth the money.

Good Luck
 
  #3  
Old 07-06-09, 01:16 PM
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Thanks diyplank for the reply.

It would be hard to put a vent fan thu the roof, but a fan could be installed at the gable end, The exisiting gable vents has screens on them, the fan could be installed in the attic blowing out so the bugs would not be a issue. I read online that attic vent fans could be a bad idea, They can pull cool air out of the living space into the attic thu tiny cracks and lights and wiring and making the heat pump even work harder.
So im still pondering the attic fan idea.
Yes there is 6" thick fiberglass insulation in the rafters on the low slope part of the roof. The insulation completely fills the 2x6 rafters, under the rafters is plywood then ceiling tex in the living area, above the rafters is felt, shingles, 1x4 striping and a metal roof without inclosures so it vents a little between the metal and shingles. What bothers me is this insulation is not vented and its whats keeping me from installing soffit vents and venting the main attic. The main attic has blown insulation on the floor. It would take a major overhaul to remove the insulation on the slopes because it is completley sealed in. Is this insulation something to be concerned about?
I thought about about removing the blown insulation off the main attic floor and installing spray foam to the rafters in the main attic to make it an unvented attic. beings it real close to an unvented attic now, but the more I research unvented attics online the more I get confused, some say do, some say don't. so who knows if its the right thing to do or not. lol
 
  #4  
Old 07-06-09, 04:03 PM
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Well, since it is finished then no. It should be fine! You just have to worry about ventilation getting to the finished part of the roof. B/c if it isn't vented correctly then you could damage your roof. But I am sure its fine!!

Well, I would put a fan in, if its really well insulated then you should be fine. Just go through where you can access things and seal stuff up really well w/ that spray foam that expands. So your attic, is it partially finished?? Can you show pics?? You can go to Image hosting, free photo sharing & video sharing at Photobucket and upload pics there and then copy and past the html code to your post. That may also help other people on here give you a better answer than me. In the winter this part of the insulation forum is hopp'in!! I am no pro but I have learned a lot reading posts on here and doing my own insulation, which is cellulose!! LOVE THAT STUFF!!
Beer 4U2
 
  #5  
Old 07-07-09, 11:02 AM
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You will need to bite the bullet!
The summer heat is coming into the home by radiation and conduction.
Those 6x2's are a large part of the problem. They are conducting the heat direct from the roof into your home.

Fibre glass is not very good at keeping heat out as glass is a conductor, the insulation part, is the air that's trapped inside the fibre glass, unfortunately this air gets hot and starts to convect within the fibreglass blanket and transfers the heat indoors.
You need to pull the ceiling down and fill the space between the rafters with polystyrene, polystyrene is a closed cell insulation that works by trapping lots of small balls of air inside a similar amount of thin plastic. Unlike fibre glass the air is trapped and cannot convect.

Try to make the polystyrene a friction tight fit and avoid having any holes as the heat will come though the holes.

Then fix sheets of at least two inch thick polystyrene, tightly butted across the ceiling to stop that heat coming out of the bottom of the joists. And finish as you wish.

Think of the wood frame of your home as being the weak link, where ever there is a direct connection between the inside of your home and the roof heat will come in.

Therefore, identify these weak points and insulate on the inside.
A white coated roof will help to reflect the heat of the sun.
Try to use insulation rather than forced ventilation as this is a lot cheaper in the long run.
 
  #6  
Old 07-18-09, 06:46 AM
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After doing a little more looking. removing the ceiling is not an option. the insulation and plywood ceiling was installed and then stud walls was put up. I did take a temp reading in the main attic. it was 109 degrees and the outside temp was 95. I guess thats not to bad with just 2 gable vents. The new metal roof that is venting between the metal and singles must be helping the attic a lot. I know it use to get a lot hotter in the attic never took a temp reading before the metal roof was put on. Im going to look into maybe blowing some more insulation into the main attic. It has blown insulation (white stuff). over the years it has settled and is packed down in places from crawling around on it.
 
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