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Old 10-09-2019, 02:34 PM   #1
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Attic Insulation Project


Hi folks, looking to redo the insulation in our attic this fall as we barely have any I think original R11. But I had a quick question about ceiling joists. I believe they are 2x6's, looking to go with a fiberglass roll or batt install simply because I can get a good deal and I will doing this project when my time permits.

If I go with let's say an R38 or R49 the thickness of that batt obviously is much thicker than that of the 2x6. So my question is, is it ok that the tops of the 2x6's are exposed and not covered or is that considered a void and should be covered?

Am I better off going with an R21 which is for 2x6 and going perpendicular with a batt roll or ideally come back and blow cellulose over top.

To get the project going first and foremost I know I need to airseal as much as I can and I plan on removing the old damaged and 60+yrs old insulation and discarding it.

Thank you in advance for your time and help.

Last edited by cbaur88; 10-09-2019 at 02:46 PM.
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Old 10-09-2019, 02:45 PM   #2
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Re: Attic Insulation Project


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Originally Posted by cbaur88 View Post
Hi folks, looking to redo the insulation in our attic this fall as we barely have any I think original R11. But I had a quick question about ceiling joists. I believe they are 2x6's, looking to go with a fiberglass roll or batt install simply because I can get a good deal and I will doing this project when my time permits.

If I go with let's say an R38 or R49 the thickness of that batt obviously is much thicker than that of the 2x6. So my question is, is it ok that the tops of the 2x6's are exposed and not covered?

Ideally I'd like to come back and blow cellulose over top but if that don't happen I want to know it was done properly. To get the project going first and foremost I know I need to airseal as much as I can and I plan on removing the old damaged and 60+yrs old insulation.

Thank you in advance for your time and help.
You have air chutes and good ventilation?

I would fill the space between the joists and then the next layer going the other way.
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Old 10-09-2019, 02:49 PM   #3
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Re: Attic Insulation Project


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You have air chutes and good ventilation?

I would fill the space between the joists and then the next layer going the other way.
I don't currently have air chutes but ventilation is good.
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Old 10-09-2019, 02:56 PM   #4
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I don't currently have air chutes but ventilation is good.
You will need them if the new level of insulation would close the lower vents.
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Old 10-10-2019, 12:22 AM   #5
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Re: Attic Insulation Project


The top of the exterior walls is often too close to the roof to install the insulation you want, thus the chutes allow you to fill more without future concerns of blocking that air flow.

Chutes can also have a flap at the bottom to hang down and protect the end of the insulation from "wind washing", air flowing through the insulation.

I'm retired but have done many infrared inspections and those top exterior corners need all the help they can get.

Bud
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