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  1. #1
    Join Date
    Feb 2014
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    2

    Question need help sorting out conflicting insulation information

    My basement wall is made of poured cement that was created in a form to look like bricks. It has the irregular surface of brick. It was insulated with a 3.5 inch blanket of fiberglass insulation with an aluminum and plastic outer surface (see picture). The blanket has been removed from the wall because several articles state, fiberglass insulation should never be touching a concrete wall because the walls will seep moisture and create mold.

    I am looking at insulation options for the stud wall I plan to erect. One of the options is rigid foam board, there are several conflicting articles on rigid foam board. Some say for support you only need to put two large plastic washers and nails to hold up the board while others say to use glue and some say you must put glue around the entire back edge of the board to stop convection of the colder air at the top of the wall with the warmer air at the bottom. Since my wall has all the irregularities of a brick wall it would not be possible to seal the back of the board (see attached picture).

    Most of the builders put the stud wall right up against the rigid foam board, they used pressure treated lumber because rigid foam board does allow moist vapor to pass through to into the home which over time would rot regular 2 by 4s. But then they put fiberglass insulation right up against the rigid foam board which is a recipe for mold. I think you would want a gap between the insulation and the stud wall and only use treated wood on the floor.

    I am now considering building a stud wall with a one inch gap from the concrete wall and cutting up the fiberglass blanket that was on the wall to put between the studs and then covering the studs with wall board.

    I am totally confused, there is so must conflicting information out there that I have a case of analysis paralysis. There must be some studies by architects that give a definitive answer to this question

  2. #2
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,776

    Default Re: need help sorting out conflicting insulation information

    How old is the house? How long has the fiberglass been in place? Is/was there any mold when you removed the fiberglass? Did the fiberglass have a vapor barrier on the room side? Is the concrete wall waterproofed on the outside?

    Consider using the foam system called insofast. Google it.

  3. #3
    Join Date
    Feb 2014
    Posts
    2

    Default Re: need help sorting out conflicting insulation information

    Quote Originally Posted by keith3267 View Post
    How old is the house? How long has the fiberglass been in place? Is/was there any mold when you removed the fiberglass? Did the fiberglass have a vapor barrier on the room side? Is the concrete wall waterproofed on the outside?

    Consider using the foam system called insofast. Google it.
    The house is 10 years old, the basement walls are dry, the outside concrete has been waterproofed, there is no mode on the fiberglass and the plastic on the outside of the fiberglass blanket is a vapor barrier.

  4. #4
    Join Date
    Dec 2007
    Location
    Tennessee
    Posts
    1,776

    Default Re: need help sorting out conflicting insulation information

    If the walls are waterproofed on the outside, they are not going to seep moisture. It does not matter if fiberglass touches it or not. Moisture happens even of the walls are waterproofed on the outside when the basement goes from being an unheated space to a heated space and the walls are insulated but no vapor barrier is used.

    If you are doing this, then I would look at the insofast system. They have all the instructions for doing it properly.

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