Insulation Against Concrete Walls

Discussion in 'Home Theater Projects' started by GrahamO, Feb 28, 2004.

  1. GrahamO

    GrahamO Auditioning

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    I am about to start my second home theater and wanted to get some information before we started framing. The room is in the center of our basement and two of the four walls are concrete. The two normal walls and ceilings will be filled with insulation to dampen to sound going to the rest of the house. My question is should I insulate the walls we are framing next to the concrete? If I don't, I don't think sound from the room will be an issue, but I worry about the sound treatment in the room since two walls will be different. I have heard that insulation in the walls has nothing to do with the sound treatment in the room, but I wanted to check before starting. Thanks.
     
  2. Shawn Keeler

    Shawn Keeler Stunt Coordinator

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    You definitely want to insulate inside all the walls. Otherwise, that empty space inside there will act like a subwoofer cabinet and resonate like crazy, adding to other possible room mode problems. Hope that helps.
    Shawn
     
  3. Jason D.

    Jason D. Agent

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    I agree 100%, I am doing the exact same thing....HT in basement with 2 of the walls against (well not touching, but leaving 2" space) 10" of concrete. Absolutely insulate those walls....mid to low frequencys will still be getting through and resonating in that space. Good luck.

    -Jason
     
  4. GrahamO

    GrahamO Auditioning

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    Thanks for your help. I will insulate all the walls.

    Graham
     
  5. Bobby C

    Bobby C Stunt Coordinator

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    Graham,

    Are these 2 walls exterior? If so there may be some issues w/ insulation touching the wall - this can be a source of condensation. I've done a fair amount of research on the issue as I have exterior concrete walls. What I'll be doing is 'studding' out the wall 1" from the wall, so the actual distance from the wall to the front of the stud is 4.5" (rather than 3.5"). This means that when I use R-13 Kraft faced insulation (which is 3.5" deep), there will be an air pocket of 1" between the wall & insulation. Don't know if this pertains or not, if so I can point you to more information.

    Bob
     
  6. GrahamO

    GrahamO Auditioning

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    I am not sure what you mean by "exterior". The basement is dug out of the ground so the only thing on the other sides of the concrete is dirt. I know I am probably missing the point. I am framing it with friends so it would be easy to do what you suggest, but I am unclear on the need.

    Graham
     
  7. CRyan

    CRyan Screenwriter

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    Underground concrete walls are moist. Water vapor is always expressed from the free side of any such wall (i.e to the inside of your room). You cannot place insulation directly agains a concrete wall where the other side faces the exterior (dirt in your case). Insulation will get soggy harboring mold and fungus. Eventually it will seep through the drywall and create stains that you will be unable to cover. You can also paint the concrete wall with a water barrier like KILZ.


    C. Ryan
     
  8. GrahamO

    GrahamO Auditioning

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    Got it. Thanks again for all the help. Given that my sub will be firing down one of the walls against the concrete, is leaving the 1 inch gap okay? I worry it will resonate in the open 1 inch cavity. Should I use the water barrier method instead? Again, these concepts are new to me so I appreciate the help.
     
  9. Nick P

    Nick P Second Unit

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    As long as you insulate the stud wall that is held off the foundation the one inch gap shouldn't be a resonating problem. Being in the location you're in (I'm just across the Ohio River myself) you're going to want to insulate those walls regardless of a home theater or not. It can get somewhat chilly down in a finished basement that is under the outside grade.
     
  10. Eddie L

    Eddie L Stunt Coordinator

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    is your outside insulated? On my place I insulated the outside with "blue board" but only after painting and troweling on Theroseal and hot tarring the joints of the block to footings. This was done to the back and side walls that were backfilled with sand. The Theroseal was also painted on the inside of these 3 walls. The front, which is a walk in, was only done with the Theoseal on the outside but much thicker, making it look like stucco. The front wall was not Therosealed on the inside as it's only open to the air, and not sand or dirt. All walls on the inside were then furred out with 2x2's and 1 1/2 in. styrofoam was used for insulation. You can use a vapor barrier of plastic to cover the styrofoam, but if your styrofoam is nice and tight this is over kill, but we did. We built in '87 and no problems what so ever with moisture of any kind. I know because we've already remodeled diferent areas, and everything is nice and dry. We're here in Alaska where there's snow, rain, freeze, thaw, but....no humidity! Hope this helps.
    Ed
     

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