Help with Insulation (Basement)

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tpirovol
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Help with Insulation (Basement)

Post by tpirovol » Mon Apr 09, 2018 9:29 am

Hi Shannon,

About 7 years ago I purchased a home that had an unfinished basement with no insulation. There are obviously 4 walls and a Rim-Joist's. I framed the entire basement and installed Tar-paper, then roxul and finally vapour barrier. At the same time I installed Roxul in the rim-joist.

Fast forwards to about 4 years ago I noticed the that there was a streak of water down the poly from the rim-joist. What I found was mold in a few of the rim-joist where the roxul met with the outside wall. That damage was hardly any but I cleaned the mold and left the rim-joist in-insulated until now. My wife would like to finish the basement and I have the below 3 questions.

1) I am reluctant to add any batt type insulation to the rim-joist. I have watched your video's if I just add 2" foam and spray foam around it to make a seal is that enough? Also to add more complications the beams are ijoists so it is very hard to do a vapor barrier there.

2) One of the rim-joist is extremely hard to get to. What can I do there? If I just leave it in-insulated will that be a problem? I could probably manage to get the 2" foam back there but I would not be able to seal it up in all the spots. This is the rim-joist that goes along the back of my house parallel to the beam. The reason it is hard to get to is they ran the venting along and parallel to that area.

3) On all 3 walls the insulation is tight to the tar-paper and the vapor barrier. On one wall I had to install the framing 2" away from the wall because of the drainage pipe. I have installed 2x6 roxul there but there is about a 1" gap between the tar paper and insulation. I have read on some sites that leaving a gap is good and another that it is bad. Here is the question do I add another layer of batt to make it tight and flush or leave the gap?

Thanks again and keep up the good work with the video.
P.S. If I could go back and do it again I would have installed 2" foam then the insulation.


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Shannon
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Re: Help with Insulation (Basement)

Post by Shannon » Mon Apr 09, 2018 10:31 pm

1) IMO The problem is not the batt insulation it is likely more of a case that you didi not have a perfect seal between the poly and the joist and underside of floor. This lets warm moist air into that cavity where there is still cold air. I would still install 2" rigid foam(sealed) against the rim and ontop of the concrete basement wall and new interior framed wall. You can then just add more roux against that for R value.

2) Could you drop the duct work, insulate and seal the area and re-install the duct work? it really should be done right.

3) that small of a gap is fine.
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tpirovol
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Re: Help with Insulation (Basement)

Post by tpirovol » Tue Apr 10, 2018 7:11 am

Thanks Shannon that is what I figured. So let me know what you think?

1)2” foam sealed then Roxul batt without vapor barrier as it will be impossible to do.

2) it will be very hard but I will most like try to and then 2” foam sealed.

3)Sounds good

Thanks Terry

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Shannon
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Re: Help with Insulation (Basement)

Post by Shannon » Tue Apr 10, 2018 7:44 am

sounds good
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Re: Help with Insulation (Basement)

Post by tpirovol » Fri Apr 13, 2018 8:51 am

Hey Shannon,

What is the best option 2" Foam sealed with foam and then Roxul or Roxul then the 2" foam sprayed? Also have you ever used the 2ft long spray foam gun? If so how easy is it to use?

Thanks T

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Shannon
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Re: Help with Insulation (Basement)

Post by Shannon » Fri Apr 13, 2018 5:23 pm

I think the 2” rigid sealed then Roxul added. I have never seen a 2’ foam gun?
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