Recent Comments and Answered Questions on Green Building Advisor

  • Steve Knapp CZ 3A Georgia | Nov 17,2017 02:13 PM EST
    Just to be clear, MemBrain is a smart vapor retarder. It and poly are not equivalent. It sounds like the home could use additional air sealing. (Here is one article on this topic: ...
  • Andrew Southam | Nov 17,2017 02:12 PM EST
    Hi everyone, I am working to build a small 100 square foot loft cabin, much like the "Cottage Life Bunkie" by Wayne Lennox. Unlike in that design, which has no insulation, I am looking to use ...
  • Armando Cobo | Nov 17,2017 02:07 PM EST
    No. All sealed crawl spaces require ventilation. IRC recommends 1 cfm / 50 sf
  • Steve Knapp CZ 3A Georgia | Nov 17,2017 02:03 PM EST
    Armando, On #3, are you recommending a ventilated crawlspace? If so, why?
  • Armando Cobo | Nov 17,2017 02:02 PM EST
    My first question would be if the HVAC system was designed, installed and commissioned properly... have all the supplies been tested for correct cfm delivery. Second, does the system has an IAQ ...
  • Armando Cobo | Nov 17,2017 01:52 PM EST
    Based on my experience in CZ3A: 1.- I never spec RB. If my attic floor is sealed, I have full R38+ insulation (always heeled framing), no HVAC in the attic, I could care less how hot the attic ...
  • Dana Dorsett | Nov 17,2017 01:33 PM EST
    Balloon framing usually has wall cavites that extend unobstructed from the top of the foundation into the attic. That has a significant stack-effect drive, and it can pull a LOT of moisture into ...
  • Armando Cobo | Nov 17,2017 01:30 PM EST
    Do you know if you have insulation on top of the roof sheathing, as in rigid foam, or spray closed cell foam on top of the roof? If not, probably the easiest is to remove existing roofing, install ...
  • Norman Bunn | Nov 17,2017 01:26 PM EST
    Dana, He plans to use can foam on the seams and use dense pack cellulose in the stud bays. The YouTube video on Ecoseal Plus vs caulk is what is leading me to go in that direction. (I would ...
  • Dana Dorsett | Nov 17,2017 01:17 PM EST
    A humidifier is almost always a bad idea. More often than not it's just band-aid for low-humidity comfort in an air leaky or over ventilated house, when the better solution would be to tighten up ...
  • Michael Prisco | Nov 17,2017 01:06 PM EST
    There is no plastic sheeting up yet so all of the moist air from the living space can reach the baffles. The house is not lived in and I assumed it wouldn't matter if I waited to put up the ...
  • Norman Bunn | Nov 17,2017 12:54 PM EST
    It sounds like you have an air sealing issue that is allowing moist air from your living space to get into your attic. Is this a cathedral ceiling or a flat one?
  • Michael Prisco | Nov 17,2017 12:37 PM EST
    The joist bays are open to the vented attic. Will they dry to the attic over time?
  • | Nov 17,2017 12:21 PM EST
    We had condensation on our windows of a newly constructed home. It was due to a broken solenoid in the whole house humidifier. The humidifier switch said "off" yet it was running unbeknownst to ...
  • Dana Dorsett | Nov 17,2017 12:17 PM EST
    You're right that foil faced sheathing would be "worth it", but with no HVAC in the vented attic, and a code-minimum R38 or more of fluff on the floor there's no rationale for additional RB. ...
  • Jon R | Nov 17,2017 12:08 PM EST
    Ask him to demonstrate an effective air seal between two sheets of OSB as the gap between them cycles between zero and 1/8 inch. Even when the foam was applied when it was zero.
  • Dana Dorsett | Nov 17,2017 12:00 PM EST
    The 99% outside design temp for Boston is +12F (and yes, it sometimes gets into negative single-digits in town). The ecocomfort online load tool isn't nearly good enough for accuracy on that ...
  • Peter L | Nov 17,2017 11:22 AM EST
    I remember reading online somewhere that claimed a 2-story home is about 20% less expensive vs a ranch home of the same size. Although the consensus here seems to be that a ranch home would be ...
  • Reid Baldwin | Nov 17,2017 10:43 AM EST
    I looked back at your 2009 article and I didn't notice major changes since then. As in 2009, building scientist recognize ventilation as important, but most homeowners still don't. Building ...
  • Ethan T ; Climate Zone 5A ; ~6000HDD | Nov 17,2017 09:50 AM EST
    My understanding is that the Minoair Boreal has been replaced by the CATU-V12 (https://www.minotair.com/minotair-boreal-12000_us/). The cooling capacity has been upgraded; I'm not entirely sure ...
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