Mildew inhibitor for indoor latex paint?

Discussion in 'Remodel Forum & Blog' started by chassis, Mar 14, 2012.

  1. chassis

    chassis Engineer

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    SE Pennsylvania
    Hello all,

    What is the verdict on using liquid mildew inhibitors added to interior latex paint? I need to repaint a bathroom due to mildew on the ceiling. The ceiling adjoins the attic and an outside wall. The attic is very cold in the winter, and moisture condenses on the ceiling and mildew is generated. The fan in the bathroom is used but doesn't seem to help the mildew situation.

    If I add mildew inhibitor to latex ceiling paint, will it help this situation? Are there other options? Thanks for any input.
  2. Dana

    Dana In the trades

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    The other, even better answer to the problem is to fix the heat leak, assuming you can access that point in the attic.

    A common thin-spot in insulation is at the top plate of the studwall, where they don't blow in fiber or stuff batts that might obstruct soffit ventilation. Sometimes wind-washing will move blown insulation out of those areas creating thin spots too. If you loosely cut'n'cobble sections of rigid XPS foam (pink, blue green, whatever) to at least 4" depth (R20) beween the joists directly on the top plate of the studwall,leaving a minimal 1" of vent space between the XPS and the roof deck, and use 1-part expanding foam (eg Dow Great Stuff) between the sides of the XPS and joists, then re-install the attic insulation right up against your stack, that section of ceiling will run much warmer, spending more time above the dew point of the bathroom air, with many fewer condensing hours.

    While your up there, assess the depth and condition of the attic insulation. If its less than 10" from the top of the insulation and the ceilng, an overblow of 6" of cellulose to even it up and fill in all gaps would be cost effective. (Even more is warranted if you heat with oil, propane, or electricity.)
  3. chassis

    chassis Engineer

    Messages:
    339
    Location:
    SE Pennsylvania
    Thanks Dana, very interesting response. It makes sense. I'll poke around in the attic to see what kind of access I have to add more insulation.

    Have you (or anyone else) had experience with mildew inhibitors as a paint additive? Thanks again.
  4. chassis

    chassis Engineer

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    339
    Location:
    SE Pennsylvania
    I looked in the attic and sure enough there was very little insulation in between the joists in the area with the mildew on the ceiling. I filled the empty spaces with insulation. Next step is to clean the ceiling (bleach and mildew killer/inhibitor?), then repaint the ceiling. I don't think I'll know if it worked until next winter when the attic is cold again.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    White vinegar, hydrogen peroxide in a 50/50 solution, then boric acid at 1c/gallon will literally shread the walls of the mold cell (killing it) and slightly bleach them. spray it on. Keep any leftover tightly capped, or the hydrogen peroxide will degrade to plain water and no longer be effective.

    If there's anything left after washing with this, use some bleach to clean it off some more. You may need a blocking primer.
  6. chassis

    chassis Engineer

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    339
    Location:
    SE Pennsylvania
    jad,

    Does this solution damage other materials, such as: ceramic tile, grout, acrylic tubs, glass or plated metal (plumbing fixtures)? Would you recommend I apply it with a sponge mop, spray bottle or something else?

    Thanks.
  7. chassis

    chassis Engineer

    Messages:
    339
    Location:
    SE Pennsylvania
    Jim, that stuff works!!! I mixed up a batch of cleaning solution, per your recipe, filled an empty Windex bottle I had from my last tile project, and sprayed the solution on the ceiling and walls. I let it soak for 5 or so minutes, then wiped the mildew off with a sponge. It came off really well!

    I found the boric acid at a Rite Aid pharmacy, in the first aid section. It came in a white plastic bottle, 4 oz., with a screw cap. Most people I asked, had never heard of boric acid. I looked at Lowe's, Home Depot, WalMart and two local grocery stores, and no one had it. One 4 oz. bottle of boric acid, with the prescribed amount of vinegar and peroxide makes about 36-40 oz of solution, which is enough for one treatment of an 8' x 8' bathroom. I applied the spray liberally to the ceilings, and about 24" down the walls from the ceiling. I'm going out to get more peroxide to make a second batch, and re-apply.

    There is still some mildew (dead now?) in the pits and cracks of the ceiling and walls. I hope the second treatment will take care of it. After the second treatment I will wash the walls with TSP and then prime with something like Kilz. Then I will paint two coats of color.

    Lots of steps with this process, but I am impressed with the results. Combined with the improved insulation job I did in March, I hope this licks the mildew problem.
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Location:
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    It's good to get some feedback...glad it worked for you. I can't claim ownership of the recipe, I picked it up on a tile forum www.johnbridge.com, but I trust the person who provided it as they have had lots of experience with it. It relies on some basic biology traits and the nice thing is that it's safe, too.

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