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  1. #1
    Join Date
    Apr 2013
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    Default Insulation/vapor barrier on cinder block home in Florida

    I'm new to this forum, thank you for taking the time to give your thoughts on my question. I live in the central Florida area in a mid 1970's cinder block home. I have had recent health issues that have caused me to have to retire out of my job as a firefighter for the city of Orlando after 10 years. It turns out the cause of my health problems is possibly linked to toxic mold that was found in my house. Black mold was found growing on the backside of all the baseboards inside our home. Full remediation has been done at this point. When our house was built the interior walls on the perimeter of the house consisted of drywall then plastic vapor barrier over a thin layer of non-faced insulation and furring strips, then the cinder block. There is only a 3/4 inch space between the drywall and cinder block.

    I had a home engineer come to the house yesterday and he said that plastic vapor barriers are not usually used in Florida due to the tropical climate and mild winters. He thinks that due to the humid heat outside and the a/c running that the plastic vapor barrier is causing condensation that is running down to the base boards. Every one of my family members that owns a home in this same area have no vapor barriers over there cinder block walls.

    Due to the mold the bottom 4 feet of drywall has been removed on all exterior walls and I am in the process of removing the old insulation and plastic vapor barrier.

    My question is what would be a good insulator to put in between the drywall and cider block that will not act as a continuous barrier like the plastic so I don't end up with condensation and more mold.

    I was looking at different types of foam board insulation which would fit perfectly in the 3/4 inch space between the drywall and block. I realize up north vapor barriers are a must but from what I'm being told down here in Florida it can cause problems like my house.

    Is there anyone on this forum that knows construction in tropical climates?

    Thank you so much for any help. My health is counting on it.
    Last edited by Fireguy911; 04-28-2013 at 09:58 PM.

  2. #2
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,902

    Default Re: Insulation/vapor barrier on cinder block home in Florida

    Have you considered putting the insulation on the exterior side of the block wall. The advantage to this is that the block wall has a lot of thermal mass and will store heat. The insulation on the exterior side will keep the concrete blocks from getting to hot during the day and cold at night.

    You would have to use rigid foam boards glued to the blocks, then a stucco and paint over that. You could apply plaster directly to the blocks on the interior side and paint with a vapor resistant primer and a good top coat of latex paint with a mildewcide added.

    The last step would be to control the humidity inside the house. I don't think anyone makes an HVAC system that works like a car, but a system that first ran the air through an air conditioner to reduce the absolute humidity (squeeze out the water in the air) and then heat it to the desired temperature would keep the relative humidity down inside the house so that condensation never forms.

    You may have to just do with a separate dehumidifier system to keep the RH between 30 and 70%.

  3. #3
    Join Date
    Apr 2013
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    2

    Default Re: Insulation/vapor barrier on cinder block home in Florida

    I hadn't thought of that. Thank you for responding. I will look into that. I bought a dehumidifier since the remediation and I am averaging about 40% humidity now. I just want to make sure I address the the interior walls properly so I don't have condensation. No sure if a vapor barrier in this climate is a good thing.

  4. #4
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,902

    Default Re: Insulation/vapor barrier on cinder block home in Florida

    The trick is to keep the inside surface of your exterior wall above the dew point for the humidity in the room. Putting the insulation on the outside of your block walls will keep the blocks closer to room temperature so condensation is much less likely.

    If your dehumidifier can keep the humidity down inside your house during the hot muggy summer, you will not have any condensation. In the winter, you need to keep the wall surface temperature above the dew point. Here is a reference that should help you understand.

    http://www.tis-gdv.de/tis_e/misc/klima.htm

    This is a German Dept. of transportation web page, but it is in English.

  5. #5
    Join Date
    May 2012
    Posts
    137

    Default Re: Insulation/vapor barrier on cinder block home in Florida

    Tens of thousands of block homes, including my rental in Central Florida, have no insulation outside, just stucco.

    The insulation you need inside is interior-installed foam panels that have an aluminum or mylar backing facing the block to resist radiant heat. Your drywall goes over that.

    Your Florida home needs to breathe, and the heat goes a long way to combat moisture, in concert with an efficient HVAC system designed for the size of your home. Too large an HVAC system will actually be less efficient in humidity control and comfort.

    Call your local power company for a free energy audit.

  6. #6
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,902

    Default Re: Insulation/vapor barrier on cinder block home in Florida

    Quote Originally Posted by daspyda View Post
    Tens of thousands of block homes, including my rental in Central Florida, have no insulation outside, just stucco.

    The insulation you need inside is interior-installed foam panels that have an aluminum or mylar backing facing the block to resist radiant heat. Your drywall goes over that.

    Your Florida home needs to breathe, and the heat goes a long way to combat moisture, in concert with an efficient HVAC system designed for the size of your home. Too large an HVAC system will actually be less efficient in humidity control and comfort.

    Call your local power company for a free energy audit.
    Just because it is not commonly done does not mean that it isn't the best way to do it. Its a relatively new way of building. It is more popular in the desert southwest but it would work just as well in Florida. It really shines where there is a large temperature difference between daytime and night time.

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