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How to insulate and soundproof with least emissions/toxicity?

mollmal | Posted in Green Products and Materials on

We live in zone 3C, and we’re thinking of putting Roxul between studs of interior walls we want sound-proofed along with double sheetrock and Green Glue to bind staggered sheetrock panels together. For external walls we’re trying to decide between a denim insulation or Roxul. The house originally had a moisture barrier on the outer side of the studs on the exterior walls and close to the house side in the attic.

My husband and kids have allergies, and my husband is very sensitive to smells. My kids both have larger health conditions as well, so we’d really like to avoid anything that may continue to emit gases or reduce the air quality inside the house. At the same time, sound-proofing interior walls is a priority, and we’ve gotten mixed and possibly out-dated messages about how or if to insulate the exterior walls.

Are the above good products to consider? Should we move or remove this vapor barrier? Will it be better for us to insulate the exterior walls or not? If using Roxul, is Safe n Sound the cleaner option and a better choice than the other Roxul for both interior and exterior walls?

Thanks so much for any advice or information you can share.

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Replies

  1. GBA Editor
    Martin Holladay | | #1

    Molly,
    Q. "Are the above good products to consider?"

    A. The products you list sound fine to me, but when it comes to chemical sensitivies, there are no rules. If you are worried that some family members may be sensitive to certain building materials, you may want to do some tests by exposing your family members to samples of these materials to see what happens.

    Q. "Should we move or remove this vapor barrier?"

    A. I'm not sure what barrier you are talking about. In your question, you mentioned "a moisture barrier on the outer side of the studs on the exterior walls," and I'm guessing that the product you are talking about is a plastic housewrap like Tyvek or Typar. This type of membrane is called a water-resistant barrier (WRB), and it is absolutely necessary that you have such a layer on your wall. It helps keep your wall dry and reduces mold risk. Moreover, this type of membrane is required by building codes.

    You also referred to "a moisture barrier ... close to the house side in the attic," and I'm guess that this is a type of polyethylene, although I'm not sure. If it is polyethylene, you can probably remove it safely -- but you will still need some type of air barrier in this location. You can use drywall as your air barrier, but you still need to pay attention to sealing any penetrations if you want the drywall to perform well as an air barrier.

    Q. "Will it be better for us to insulate the exterior walls or not?"

    A. Unless you live in Hawaii, your exterior walls need to be insulated -- to make your house comfortable, to lower your energy bills, and to comply with building codes.

    Q. "If using Roxul, is Safe n Sound the cleaner option and a better choice than the other Roxul for both interior and exterior walls?"

    A. I'm not sure what you mean by "cleaner." As far as I know, the density of Safe n Sound has been optimized for sound reduction, but otherwise it isn't any different from other types of Roxul insulation.

  2. mollmal | | #2

    Thank you very much for the help!

    Now I'm wondering if we should use roxul comfort board or another mineral wool rigid board outside the studs to keep the studs dry and insulated, as opposed to using roxul bats between the studs. ?

    Also, should we just skip adding a moisture barrier or use something like MemBrain on the interior side of the wall?

    And where does an air barrier go, and what is a good product to use for this (unless interior drywall is good enough to count as an air barrier)?

    Also, we don't plan to use the air conditioning much if at all, and we don't have any overly wet rooms like pools or greenhouses.

    Thanks again! Our builders are just used to putting in pink fiberglass and a sheet of polyethylene as a vapor barrier, I think. We're really trying to build smart to save our energy and health. If you have additional advice on construction of walls to optimize these goals in zone 3C house that's inland and not right on the water, I'd love to hear the products you'd recommend and the order they would go in from interior to exterior of the exterior wall.

    We also have some exterior walls exposed that are just studs and a thick black plastic on the outside of the studs (polyethylene?). Is it wiser to just leave this plastic, put in roxul bats between studs and then drywall on the inside - or should we take out the plastic sheets?

    Thank you!!

  3. GBA Editor
    Martin Holladay | | #3

    Molly,
    Are you working with an architect or builder, or are you doing the work yourself? Because you have lots of elementary questions, I'm beginning to think that the best way for you to go forward with your project would be for you to hire a builder to help you.

    Q. "Now I'm wondering if we should use roxul comfort board or another mineral wool rigid board outside the studs to keep the studs dry and insulated, as opposed to using roxul bats between the studs?"

    A. Either approach (or both) can work, as long as (a) you meet minimum code requirements for the R-value of your wall, and (b) you know how to install furring strips on the exterior side of the continuous insulation layer that you plan to install on the exterior side of your wall sheathing. It's trickier to install furring strips over mineral wool than over rigid foam.

    Q. "Should we just skip adding a moisture barrier or use something like MemBrain on the interior side of the wall?"

    A. There is no need for a moisture barrier on the interior side of the wall. In some cold regions of the U.S., building codes require a vapor retarder (not a "moisture barrier") on the interior side of walls, but those requirements don't apply to your location (Zone3).

    Q. "Where does an air barrier go, and what is a good product to use for this (unless interior drywall is good enough to count as an air barrier)?"

    A. For more information on air barriers, I suggest that you read this article: Questions and Answers About Air Barriers.

  4. charlie_sullivan | | #4

    The sad truth is that hiring a builder or architect who's competent in these things is way more difficult than it should be.

    Molly says, "Our builders are just used to putting in pink fiberglass and a sheet of polyethylene as a vapor barrier, I think." If they are putting a sheet of polyethylene in, they are not the right people to count on for advice on these things.

    So, like many of the people who come here for advice, you either need to do what you are doing--learn more about this stuff than the professionals who do it for a living know--or learn enough to be able to interview builders until you find one who actually knows more than you do.

    I think Martin has answered most of your questions. I hope you'll come back with more if reading what he's suggested leads to more questions. I want to reiterate the suggestion to buy some samples of the materials you are considering and live with them too see if anyone reacts to them.

  5. user-2310254 | | #5

    @Molly. Where do you live? Zone 3C covers a lot of territory.

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