Is it mold?

New_Mexico_WillNew_Mexico_Will Registered Users Posts: 107 ✭✭
in In the Weeds--Member's Choice #1
Below are 2 pictures of the paper side of some fiberglass insulation.  Normally mold would never be a concern here, it's just not something you think about in the arid Southwest.  However, I put a ventless propane fireplace in this building last winter, and they produce quite a bit of humidity.  This is a nice bonus for the winter in New Mexico, where relative humidity is usually in the single digits.  Buuuut now I am noticing this.  Strangely, some of it has started recently, and humidity is around 20%.  I fired up a dehumidifier and it hasn't generated a single drop of water.  What do you think?  Is this mold?  Should I just replace those pieces of insulation and start running dehumidifiers for the winter?



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  • mcgivormcgivor Solar Expert Posts: 3,854 ✭✭✭✭✭✭
    #2
    Sure looks like mould, perhaps you've created an environment inadvertently for the spores to propagate on by not using a vapor barrier, which causes moisture to form on the warm surface. Being the paper is organic offers the spore something to feed on, a mild solution of of chlorine bleach will kill the mould in the short term but an inorganic plastic membrane, or vapor barrier would provide better results long term, I would think.
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  • New_Mexico_WillNew_Mexico_Will Registered Users Posts: 107 ✭✭
    #3
    Thanks for the comment McGivor.  There seems to be a lot of arguing around these parts about weather a vapor barrier is needed.  I do plan to add one after the electrical is done.  I guess I work too slow.  It's easy to replace the insulation now, so I'll just do that and then vapor barrier.
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  • BB.BB. Super Moderators, Administrators Posts: 33,082 admin
    edited October 2020 #4
    Have not done the calculations for propane, but for gasoline, every 1 gallon of gasoline burned produces 1.5 gallons of water.

    I am not a fan of ventless heaters--And even gas stoves without a power vent can make the kitchen walls a mess (natural gas leaves a sticky film on walls/vent hood that is not fun to clean).

    Humidity wise... Mold will grow when it is >60% relative humidity for 3 days (the spores then "activate" and grow). So, if the humidity is over 60% for three days, you have an environment where mold will grow.

    Note that cold objects (such as insulation and studs to exterior walls) can create local spots of higher than "room" humidity (as temperature drop, the RH goes up).

    If this is mold (vs dust and static charge in dry air atrracting dust), you don't want to get that started. I have used spray bleach formulated for removing model on walls--Works very easily and quickly (must be much stronger than normal 5% laundry bleach).

    https://www.homedepot.com/s/mold remover?NCNI-5

    Used this on a room that was poorly ventilated and it worked great (and improved ventilation, removed potted plants, etc.). Mold did not return (was a person that like warm/humid room for sleeping--I guess).

    Then there is the old dehumidifier:

    https://www.homedepot.com/b/Heating-Venting-Cooling-Air-Quality-Dehumidifiers/Best-Rated/N-5yc1vZc4l8Zbwo5q

    Can be a relatively big user of energy--But for some closets/storage areas/laundries/etc.--May be needed).

    And for very air tight homes--An energy recovery ventilation system:

    https://www.ecohome.net/guides/2362/ventilation-air-exchangers/

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Dave AngeliniDave Angelini Solar Expert Posts: 6,397 ✭✭✭✭✭
    edited October 2020 #5
    Studs do not look like drywall was over them. Might be your problem !

    https://www.certainteed.com/insulation/resources/do-i-need-vapor-barrier/
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  • New_Mexico_WillNew_Mexico_Will Registered Users Posts: 107 ✭✭
    #6
    It's new construction
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  • New_Mexico_WillNew_Mexico_Will Registered Users Posts: 107 ✭✭
    #7
    Some great links-thanks Dave!
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  • New_Mexico_WillNew_Mexico_Will Registered Users Posts: 107 ✭✭
    #8
    Dave Angelini said:
    Studs do not look like drywall was over them. Might be your problem !

    https://www.certainteed.com/insulation/resources/do-i-need-vapor-barrier/
    There is some good info there, but WOW is that map useless.  It covers the desert I live in now, the crazy humid weather in Ithaca, NY where I grew up, and goes all the way to Canada for Zone 5.  There are crazy differences within that zone.
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  • New_Mexico_WillNew_Mexico_Will Registered Users Posts: 107 ✭✭
    #9
    Here is an interesting video, with several sources, that discourages interior vapor barrier.  Hmmmm

    https://www.youtube.com/watch?v=q8fOMBlfh3A


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  • Dave AngeliniDave Angelini Solar Expert Posts: 6,397 ✭✭✭✭✭
    #10
    I live in an area that can go either way also with a vapor barrier. I have seen open walls, in many homes, after many years with and without a barrier. No issues!

    I think your problem is you did not have drywall and you ran that heater, which is fine for construction but should be retired and replaced with a better choice, for obvious reasons. Good Luck ! 
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  • New_Mexico_WillNew_Mexico_Will Registered Users Posts: 107 ✭✭
    #11
    Agreed, Dave.  I'll need to use it for another winter, then it will just be backup for the wood stove, so it will rarely kick on.  I'll get a couple dehumidifiers and pay close attention to it this winter.  I just ordered a couple solar vent fans too.  Thanks for your input.
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  • New_Mexico_WillNew_Mexico_Will Registered Users Posts: 107 ✭✭
    #12
    Turns out it's NOT mold.  I noticed the same thing happening on insulation in my shed, where the humidity is whatever the arid southwest provides.  

    That had me scratching my head, so I had it tested.  Not mold.  It is actually the black asphalt glue that holds the paper to the fiberglass, and in very DRY environments the paper can wick the glue through, so it appears on the paper side.  I'm pretty happy about that!
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  • Dave AngeliniDave Angelini Solar Expert Posts: 6,397 ✭✭✭✭✭
    #13
    Thanks for the update! 
    "we go where power lines don't" Sierra Nevada mountain area
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  • littleharbor2littleharbor2 Solar Expert Posts: 1,844 ✭✭✭✭✭
    #14
    I was ready to suggest it was an overspray event as I read down the thread and there was the answer. Mold on open, newly installed insulation isn't very likely.

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  • Dave AngeliniDave Angelini Solar Expert Posts: 6,397 ✭✭✭✭✭
    #15
    I have seen mold do this BTW when heating during a wet winter without drywall. It is a reason there is a building code, and you can't get a certificate of occupancy until drywall and the rest of the list is complete. I agree it is unlikely in New Mexico and great that it was from the insulation binder.
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  • New_Mexico_WillNew_Mexico_Will Registered Users Posts: 107 ✭✭
    #16
    If I went to city hall and fell to my knees and begged for a certificate of occupancy, or any kind of inspection,  I would leave disappointed.  Things are different here.
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  • Dave AngeliniDave Angelini Solar Expert Posts: 6,397 ✭✭✭✭✭
    #17
    It can be the same up here in the Sierra as far as building code inspections. Pretty loose if you are remote.
    My point is the code is there for a reason. Living with exposed fibreglass is not good for you either. Everytime a door is opened.....
    I have seen alot in my years with all types of offgrid, not too many nightmares so that is good!
    "we go where power lines don't" Sierra Nevada mountain area
     http://members.sti.net/offgridsolar/
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