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Community and Q&A

Insulation and plumbing on new construction in Michigan

Carolyn Farrow | Posted in Green Products and Materials on

Hello,

We are currently in the process of framing a new construction home in Metro Detroit (Michigan). Our priority lies in building the most “nontoxic” home we can, but also want energy efficiency. I have two questions:

1. What kind of insulation do you recommend? I am worried about the moisture and rodent issues with blown in cellulose, but I am not sure if Airkrete is going to be in budget. Any experience? Any contractor recommendations from anyone in my area?

2. What are your thoughts about PEX piping. It seems standard but I am little concerned about all of our water going through plastic pipes.

Thank you!

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Replies

  1. Charlie Sullivan | | #1

    I hated the taste in the first month after the lead-soldered plumbing to my kitchen sink was replaced with PEX, but whatever was leaching out is surely less harmful than the lead was, and likely less harmful than the copper. And polyethylene is a relatively benign plastic as plastics go--it's used in medical implants, for example. Moreover, whatever it was seems to have dissipated after some months (I wasn't very scientific about assessing it).

    However, if you want to be surer of avoiding any taste or health impact, there are polypropylene pipes that are better than PEX on both accounts. The only problem is finding a contractor who is equipped with the knowledge and tools to use it. Here's one company to look at, that might help you find whether there are installers near you:

    http://www.aquatherm.com/

  2. Brian P | | #2

    I'm asking this to help...have you thought about your questions on a larger scale rather than focusing on these specific issues?

    If you're already framing, I'd be concerned you haven't thought this through, especially related to #1.

    1. If you haven't done so, you should be thinking more along the lines of the entire wall system, the roof/attic setup, windows, doors, and more. What will be your air barrier for air sealing? Siding setup? Interior finish?

    For preventing moisture and rodent issues, you'll want to be more concerned with how well the wall system is built versus the specific insulation material.

    If a higher performing home is a serious goal, you may want to pause for a second and work out these details. Maybe hire a consultant to help you plan this out....or do tons of research on your own by looking at what other successful home builders have done in colder climates.

    2. It's easy to get focused on specific health/toxicity issues. Besides focusing on PEX, have you thought about other things (that may be more of an issue) like radon, carpeting, and your HVAC plan?

  3. User avatar
    Dana Dorsett | | #3

    Regarding # 1:

    Blown cellulose has no more rodent issue (and potentially less) than any other fiber insulation. The borate fire retardents are an eye irritant.

    Blown cellulose also protects structural wood from moisture by wicking and safely storing wintertime moisture loads from diffusion/air leaks, reducing the peak & average moisture content of the wood. The lowered average moisture content limits the mold growth potential, as does the borate fire retardent.

    Blown cellulose has the lowest overall lifecycle environmental impact, since it's primary feed stock is recycled paper.

    Rock wool batts or dense-packed new-school fiberglass performs well in walls, at a somewhat higher R-value (and usually higher cost) than damp-sprayed or dense packed cellulose. Neither buffers anywhere near as much moisture as cellulose, nor do they have as much thermal mass, a benefit that's small but measurable with dense packed 2x6 framing, and becomes substantial in high-R dense packed assemblies.

    Rock wool has the lowest chemical concerns, using only modest amounts of organic materials as binders, most of which is cooked off in the manufacturing process. As long as the assembly stackup and air sealing is adequate for keeping the wintertime moisture build up in the wood to modest levels, this is probably a good bet.

  4. User avatar GBA Editor
    Martin Holladay | | #4

    Carolyn,
    I don't know who told you that cellulose insulation is associated with moisture problems and rodents.

    The best way to avoid moisture problems (with any insulation, including spray foam and rigid foam) is to design your wall well. Most moisture problems are caused by wind-driven rain, so include a ventilated rainscreen gap behind your siding, and pay attention to wall flashing at all wall penetrations.

    The best way to keep rodents out of a house (regardless of what insulation you choose) is to strive for airtight construction, or as airtight as you can manage. Fewer holes means fewer rodents.

  5. User avatar GBA Editor
    Martin Holladay | | #5

    Carolyn,
    The PEX vs. copper debate has been beaten to death. Here's the short version: both copper and PEX have long track records, and neither type of tubing is associated with any human health problems. (Lead in solder used on fittings for copper tubing can cause problems, but leaded solder has been removed from the market for decades.)

    More on PEX vs. copper:

    How Safe is PEX Tubing?

    What is the greenest and best material to use for indoor plumbing?

    PEX vs Copper

    Water supply - PEX?

  6. Carolyn Farrow | | #6

    Thank you everyone. We do have a builder, but he is not well versed in green building unfortunately. We planned to do airkrete and are building the house as airtight as possible within our budget. However, due to issues, airkrete is no longer an option. The moisture and rodent issues were gathered from my online research of the cellulose insulation. Unfortunately, I was set on airkrete so I have not done as much research as I would have liked.

    What are some recommendations for getting the home as airtight as possible? We are using fiberglass windows (Marvin Integrity Ultrex), Hardie Board siding and cultured stone. Haven't tackled the drywall issue yet. We are installing a geothermal system. The house will have a passive radon mitigation system installed before the concrete slab is poured. We will have hardwood flooring with no-voc finishes throughout.

  7. User avatar GBA Editor
  8. User avatar
    Dana Dorsett | | #8

    Caulking the framing to the sheathing at every stud bay prior to insulating is a good start, as is caulking doubled up studwall top plates to each other, and the bottom plate to the subflooring, and sealing all electrical & plumbing penetrations of the framing & sheathing with can foam (even lateral electric runs between stud bays.

    Air sealing is a whole subject unto itself. It's neither hard nor expensive, but requires some attention to detail. I'm sure Martin can point you to multiple blog bits on this site covering the topic.

    I've never personally seen rodents nesting in cellulose insulation. The closest I can think of was a squirrel that broke into a bale of (fully compressed, in the bag) cellulose in my garage a few years ago- he removed about a baseball sized portion of material (making a big mess of the garage), but didn't use it for nesting material. (I eventually found the nest which was in a partition wall between the garage and the house.) I've seen plenty of mouse nests in fiberglass (both blown and batt), and some in open blown attic rock wool.

    Geothermal heating systems are often far less bang/buck than going higher-R on the house. Using modulating air-source heat pumps for heating & cooling and spending the difference on rooftop PV usually pencils-out better. There are exceptions to prove the rule though.

    An IRC code mininimum wall for climate zone 5A (that would Detroit) is 2x6/R20 (see: http://publicecodes.cyberregs.com/icod/irc/2012/icod_irc_2012_11_sec002.htm ) But it's financially rational to go higher than that. An R20 wall with R8 continuous sheathing would have sufficient exterior R for dew point control at the sheathing, which would give it great moisture resilience since the interior side can be left relatively vapor-open, with only standard latex paint as the vapor retarder, which maximizes drying rates, and minimizes mold risk. That can be done with 2" rigid rock wool if you can't stand the thought of rigid foam. That would be a ~50% uptick in whole-wall R (after factoring in the thermal bridging of the framing. It would require deeper masonry ties for the stone veneer, but it's not a difficult or expensive build compared to using Airkrete insulation everywhere (!). If not R20 cellulose (which would enhance moisture resilience even further), R23 rock wool batts are a standard product, and R8 insulating sheathing would still be adequate for dew point control.

    I'd still recommend R60-R75 cellulose in the attic though. Blown rock wool is treated with light oils to keep it from binding in the blower. It would work, but wouldn't have lower VOC emissions than cellulose, nor would it have a cost advantage.

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