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Spray foam in rim joists, advised to remove

suect | Posted in General Questions on

We have a 2013 home in WI.  Last year the perimeter of each section was sprayed with closed cell foam and fiberglass insulation was laid over it.

I was advised by our local energy program to remove the closed cell foam. He stated the theory  behind this is the fresh air is needed for the home.  Sealing this has elevated the level of air exchange to the main floor.   New windows have been installed and attic penetrations have been sealed prior to this.

The gentleman suggested use of bath fans to pull out stale air and the opening in the rim joist would be the fresh air source. 

We have noted less than fresh air since all the seal work has been done but would this be the best action to take?


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  1. Expert Member
    BILL WICHERS | | #1

    No, you don't want to make leaks the source of your fresh air intake -- you can't control leaks. I would NOT remove the spray foam. What you should do is consider installing an ERV, which is made for this purpose -- an ERV will bring in fresh air (the "V", ventilation, part), but will do so in a way that minimizes energy loss (the "ER" part, for "energy recovery"). An ERV is basically a fan and a heat exchanger in a box.

    It amazes me that an energy auditor would advise the removal of insulation in a key place like a rim joist as a way to improve air quality in the home. The better solution to air quality is to seal the home, which helps with energy efficiency, and then use a ventilation unit like an ERV to allow for CONTROLLED ventilation.


  2. Renovations102 | | #2

    Uh... no.

    As Risinger says "build tight, ventilate right," in other words, ventilate on your terms. This "we need leaky houses" mentality seems to refuse to go away...

    Think about what he is saying... Turn on bath fans and pull all the heated/conditioned air OUT of the home!

    Simply ERV, HRV, CERV the whole house if you have a ducted system.

  3. Expert Member
    NICK KEENAN | | #3

    Have you had a blower door test done? I wouldn't assume the house needs ventilation unless you've measured the actual leakage. I also agree with everyone else that relying on leakage for ventilation is not what you want.

  4. suect | | #4

    I appreciate the replies.

    The last blower door test was prior to sealing, new windows and added insulation. None since.

    Construction:stale odors seem to be lingering until we crack open a window or two.

    It’s interesting as I had brought up a ventilation system which was discouraged by this person stating “they can be troublesome if not set up on the initial build.”

    Our home is 3000 sq Ft. ranch with several cathedral sections. Year round ventilation would be ideal. If allowed, is there a unit(s) with good reviews by the professionals? I would start my search looking for HVAC specialists who work with that brand.

  5. 1869farmhouse | | #5

    I’d never remove the closed cell. Even if you did a blower door test, and it was determined you DO need more ventilation, and even IF you decided and ERV/HRV was not the best choice for whatever reason - I’d still install mechanical supply air 10/10 before I intentionally made something leaky. I never say this... but I’d be second guessing anything this individual is advising.

    1. suect | | #6

      I’m glad to hear the responses, the work suggested would be torturous.

      Could you clarify what 10/10 is for mechanical ventilation?

      1. Expert Member
        NICK KEENAN | | #8

        I think he means "ten times out of ten."

        1. 1869farmhouse | | #9

          DCContrarian speak my language haha. Apologies if I was unclear, ten times out of ten was exactly what I was going for :)

          1. suect | | #10

            Thanks! So far no mechanical ventilation but seriously considering. Will need to learn a bit more about them.

  6. user-5946022 | | #7

    The person who gave you that advice needs additional training. It is absolutely ridiculous advice.
    I would not rely upon anything that person said.

    You have worked on sealing your home, which is great. IF you need a source of fresh air, it needs to be CONTROLLED. There are many ways to do this correctly. Brining in fresh air through uncontrolled leaky locations is not the correct method.

  7. Patrick_OSullivan | | #11

    > The gentleman suggested use of bath fans to pull out stale air and the opening in the rim joist would be the fresh air source.

    It's implied in all the replies, but I'll say it more explicitly. RUN, do not walk, away from this person. To put it in perspective, imagine you hired a plumber who told you "eh, it's okay if some of the pipes leak" or an electrician who said "it's good when breakers trip; then you know they're working!"

    1. jonny_h | | #12

      But surely you know it's important to have fresh water! If the water sits in the pipes for too long, it gets stale. So, when your faucets are dripping and your pipes are leaking, it's good because it keeps the water flowing and ensures you have enough fresh water available when you turn on the tap!

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