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Attic Insulation

Discussion in 'The DIY Room' started by ReelFaster, Oct 9, 2019.

  1. ReelFaster

    ReelFaster

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    So am thinking of redoing the attic insulation above our bedrooms this fall. Ideally I'd like to use blown in cellulose but this project will be done when time permits so batts or fiberglass rolls will be used so I can work on it whenever and not at the mercy of a rental machine. First and foremost I will air seal the attic as much as possible.

    But my question is if I go with let's say an R38 or R49 batt 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/filled in? I am thinking it should but wanted to confirm!

    Am I better off going with an R21 batt which is for 2x6 and going perpendicular with a batt roll or coming back and blow cellulose over top? I will be removing all the old insulation as its 60+yrs old and a lot of it damaged plus I need to remove to air seal. I may keep some to insulate the exterior attic wall. Thanks in advance gang!
     
  2. jtstromsburg

    jtstromsburg

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    I have used R38 and it usually fills the voids above the rafters/joists on its own. Another option could be to use R22 or whatever and then blow in another 6 or 10” later on


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  3. ReelFaster

    ReelFaster

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    Thanks, that is good to know. Ideally we all want to achieve highest R value but its costly and if I can upgrade to R38 it's going to be a big upgrade on what is up there now which I think is R11.

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  4. papadave

    papadave

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    IMO, put the R-19 (or 21) between the 2X6, then lay whatever else perpendicular to that. Provides a bit of a thermal break. 2X6 might be an R-2 or something pretty pitiful.
    Make sure the 2nd layer is butted nice and tight together. I redid the stove room a few years ago with R-19, then R-30 across those. Probably the warmest room in the house (even w/out the stove running).
    I've heard that with a helper, it's possible to do an entire attic in 1/2 day with blown cellulose. No personal experience with that though.
     
  5. brenndatomu

    brenndatomu

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    My vote above...
     
  6. papadave

    papadave

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    What's the plan for a vapor barrier once the old stuff is out? What's the original insulation?
     
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  7. ReelFaster

    ReelFaster

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    Looks like there is already a paper vapor barrier laying on top of the sheet rock. Then some yellow loose wool material and some fiberglass batts with a foil backing on top of that with foil facing up towards roof. So essentially two vapor barriers which from my reading isn't proper.

    Just re looking at it all it's a beast of a job just shy of 1000sqft not to mention cost. Need to rethink this maybe reuse some of old stuff. Thought was R11 or R13 but actually R22 plus the loose material. Just gonna be a pita to air seal.

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  8. Jack Straw

    Jack Straw

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    Wood is R1 per inch.
     
  9. ironpony

    ironpony

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    Insulating an attic, whew. I would figure out how much time and materials will cost me. Then I would have a company give me an estimate.
    By the time you put in all the baffles lying on you belly on rafters, fun fun. Some things aren't worth the savings IMO.
    Insulation companies are usually pretty economical, blown in anyway.
     
  10. papadave

    papadave

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    Good info, thanks for the clarification Jack.
     
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  11. papadave

    papadave

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    If that gets torn or cut, use some tape (not duct tape) to seal. It's not really laying on top of the rock, but stapled on the face or just inside the 2X.
    If you can, do what IP ironpony suggests. At least get a couple estimates.
    Not to mention all the sealing, etc.
    How are your knees, ReelFaster ? Even that fairly small attic will feel MUCH larger once you're up there crawling around for a while.
     
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  12. ReelFaster

    ReelFaster

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    I would but I simply don't trust anyone but of course there are exceptions. I have seen and heard about so many crap jobs being done especially in insulation. Why pay for a half bleep job when I can do a better than half bleep job myself with a little time and effort. They come in and blow over top of what you have and that's it. Who's going wading around in a sea of loose insulation to ensure they air sealed everything and covered all the can lights properly? I just have peace of mind knowing what I did up there.

    This is a walk up attic, very big and spacious so it's not as bad as you maybe thinking. My knees are good and I am still fairly young and fit at 41. The problem am having wrapping my head around is the space that needs to be done, just shy of 1000 sq ft.

    Wasn't aware I had loose insulation along with batts that are R22/24 so for cost wise I may re-use what I already have between the joists and go perpendicular with a roll of fiberglass or blown in. But being what's already there going to be a pita to air seal. O and did I mention there is particle board covering half the attic space that needs to be ripped up, yes fun!

    Thanks for the help fella's!
     
    Last edited: Oct 10, 2019
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  13. papadave

    papadave

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    Our attic is only slightly larger. I've been working on redoing the insulation up there as I can. If you can talk someone into at least handing stuff to you, the job will go MUCH quicker.
    I watched a Matt Risinger episode recently where a crew used a huge vacuum to suck out all the old blown in from his attic, air sealed, then blew in all new.
    :popcorn::ithappened:
     
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  14. ReelFaster

    ReelFaster

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    Thanks papadave I too saw a few videos on youtube of them doing the same thing sucking out the old. I have another attic above our kitchen, dinning, and living room :headbang:.... about half the size. They have can lights and man I can feel the air being sucked out last winter.

    Working up the courage to tackle this, don't want it to be one of those started and never finished but I realize anything I start and do will be an improvement and I can take my time & do what I can when I can :yes:

    20191009_170853.jpg 20191009_171008.jpg 20191009_171255.jpg
     
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  15. papadave

    papadave

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    A lot of leakage occurs at the top plates of walls. Obviously, any penetration as well. If you see dark areas on fiberglass, it's a good sign of air leakage. (Fiberglass doesn't really stop air flow much).
    That space is huge compared to mine. I wouldn't have a problem doing that attic, and my knees suck. No, I'm not coming to Jersey. :rofl: :lol:
     
    Last edited: Oct 10, 2019
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  16. ironpony

    ironpony

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    make sure all your can lights are IC (insulation contact) rated or you have the proper clearances.
     
  17. ironpony

    ironpony

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    looks like the attic in the house I am restoring now. I am 6'2 and can walk around the whole thing 12/12 hip roof 1900 house. With 4' knee walls I can probably put a 20x20 room up there.
     
  18. bushpilot

    bushpilot

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    I'd blow in cellulose. With my wife we did an attic to R38 in a few hours, it is actually quite easy and quick. Also, cellulose seals the small cracks pretty well itself.
     
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  19. fox9988

    fox9988

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    Me and a friend blew ~1800 sgft in a few hours. It would be much cheaper and faster than batts.
     
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  20. ReelFaster

    ReelFaster

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    Thinking that!! Sill have to remove the batts to air seal and they have the foil facing up so I'd have to flip them all. Thinking blowing it in might be a phase 2 project.

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