DIY Basement Insulation Video

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• Awesome job Todd!

• Question about using foamboard to insulate basement wall.
  At the end of the video,you mentioned not to use Poly against a concrete basement wall. What is Poly?
  Also, it didn't seem that you glued the foamboard against the concrete. Isn't it better to glue the foamboard so that warm air doesn't convect behind the foamboard and create moisture?
  Also, you mentioned that concrete is full of moisture. Wouldnt it be better to seal the wall first with a concrete sealing paint to prevent moisture from bleeding out from the concrete, then glue the foamboard to the concrete wall to prevent the warm air from conctacting the concrete, then put up the framed wall with fiberglass?
  I just inspected a wall that had foamboard between the studs and the concrete. The foamboard was not glued to the wall, and the wall was covered with condensation (in winter), which was running down the wall and out from the bottom of the baseboard.
  Thanks, sw

  • Sam - Poly = Plastic

    Gluing it to the wall will only do one thing and that's hold it tighter. Gluing won't stop warm air from getting behind the foam, that's accomplished by sealing the foam. You can seal the concrete but most of those products rarely work as advertised so it's a waste of money and time in my opinion. Remember, with this approach we're using the foam board as the vapor barrier. Water behind the foam will do no harm to it.

    Putting foam board between studs doesn't work. You need a continuous foam layer behind the studs. Putting foam between studs won't stop moisture from getting behind.

• Todd,

  Great video, have a couple of questions.

  In the video when you showed installing one of the panels vertically, you had said to make it tight against the floor, and also against the bottom of the joist. Where the wall runs parallel to the joists, it looks like you stop the blue board at the top of the wall. And then you also talked about using the foil face insulation at the rim joist level.

  In the article for basement insulation detail
  (http://www.homeconstructionimprovement.com/basement-wall-insulation-detail/) you say to "Install rigid expanded polystyrene insulation from the slab up to the top of concrete (masonry) wall. Install the same insulation along the top of the exposed foundation wall and then up along the rim joist to the bottom of the sub-floor."

  Is it better to use blue board to top of wall, and along top of foundation, and then use the foil face for the rim joist area, or is it better to use blue board everywhere all the way up to the subfloor?

  For the wall that is perpendicular to the joists, where you had the blue board tight from floor to bottom of joist, did you use anything for the top of the concrete wall and anything for the rim joist there?

  Thanks in advance

  • Steve - I guess I could have been a bit more specific in the video huh? The simple answer is you want to completely seal from the basement slab all the way up the concrete/block wall, over the top of it and up the rim joist. I typically use XPS foam against any concrete and foil faced on the wood. Foil faced has a higher R value but it doesn't interact with concrete well (it will deteriorate).

    I hope that helps.

    • So the way you did it in the video then, where you used blue board to top of foundation, and also along the top of the foundation, and then use Foil faced in the rim joists?

      Thanks

      • yes.

    • Todd,
      What's your opinion of putting two 1 1/2" pieces of polyiso back-to-back in the rim joists?
      Thanks.
      Roger

      • Perfectly acceptable...good luck.

• You indicated that sealers were for the most part ineffective for the intended purpose of waterproofing concrete or masonry walls. Yet I have talked with a number of contractors who swear by a 'slurry' admixture made by Xypex. Others have mentioned Drylock (have no practical knowledge of this one). If one is dealing with a retrofit situation, would not the purpose of a hydrophilic crystallizing waterproofer such as Xypex have merit in prohibiting wicking of moisture up the concrete and through the sill plate?

  • Jim - In some situations sealers can certainly improve the amount of water vapor that escapes from concrete. However, trying to plug leaks from the inside is like trying to put your finger in a hole at the bottom of an 8 foot high dam. The reality is that hydrostatic pressures will almost certainly surpass any chemical sealer. I'm simply suggesting that sealers are not a cure all for fixing basement problems and far too many people rely on them.

• Thanks for the great video!!! I was not planning on insulating between the floor joists above the basement as shown (but not mentioned) in the video. Not a problem I hope?
  I also was planning on just doing the foam board on the walls and no fiberglass between the studs. I think you mentioned that was okay if it met the code?
  Thanks for all your replies to everyone. They are always very informative!!

  • Not a problem, that house has radiant heat hence the insulation in the floor above. You are correct on the no fiberglass as well.

    My pleasure!

• On the rim joist insul......
  My house has black roofing type paper run between the end of the floor joists and the outside brick.
  I'm thinking you just leave it there as is and put the foil backed foam against it and foam as shown on the video?
  Thanks.

  • That will work fine. Good luck.

• Todd,
  I have had a flood in my crawlspace recently with all this rain and am wondering if I need to take the blue board down off the walls of the crawl and clean them with a bleach solution to keep mold growth between the blue board and the cinderblock crawlspace wall/foundation away. Also they were glued to the wall and now are not so much. Can I just wipe them down with the bleach solution and put them back up? Or do I need to cut off all the old glue before I put them back up? The Crawlspace is unfinished with a dirt floor with a 6 mil vapor barrier over the dirt.
  Please advise.

  • You shouldn't have to do anything unless there is another source of food for mold to grow. Do you see signs of mold growth?

• Hey Todd,
  Done the rim joists (among other things) lol
  And I have my blue board ready to go.
  Question do you do any rim insulation on the wall that is parallel to the floor joists? There is no real cavity there but just a 2x10 running parallel to joists. Maybe a small 2" lip where it rests on the sill plate. So leave the wood bare or foil foam board in front of?

  Similarly, in the rim joist area as shown in the video I have two windows that have a header on top. Therefore the space between the joists doesn't just go to outside brick but has a 2x10 filling the cavity. Would you put the 2" foil faced foam in front of the 1 1/2"
  thick wood or use 1/2" foam instead? Or leave wood bare?

  One for the blueboard. If you have any gaps that are not tight, would you foam them than scrape foam flat and still tape?

  Thanks again. Sorry to be long winded but without pictures I was just trying to be clear.

  • Not 100% clear on your questions. However, I'll do my best to give some response.

    - Ultimately you want every 'exterior' surface to be insulated. Sometimes the area between the rim joist and first joist (parallel) is quite tight and it's difficult to insulate. Even if the space is tight you want to get as much insulation in there.

    - You want to have insulation continuous from the wall, down the rim joist, over the top of foundation wall and then down the face of foundation wall. Visualize a continuous layer of insulation from the basement slab up to the attic.

    - I try to insulate everything up to the window, then build extension jambs for the windows and insulate up to the jambs.

    - Yes, you can fill gaps with spray foam.

    • Thanks for the help. (again)
      I think you got me straight on the parallel joist question.
      *** If there is say, a 1 1/2" lip on the sill plate you would insulate that and be against the outside 2 x 10.

      I know they have 1 1/2" blue board. Should you use that there or can you stack 3 pcs. of 1/2" foil faced foam?
      I have only seen 2" or 1/2" foil faced.

      • Either will work.....R value is additive. Good luck.

• . Thank you for the great video and article. I am renovating the basement that was poorly done and had to stop my contractors mid way :-) They were putting fiberglass straight to the foundation wall. Now, I won't use boards but will go with a spray foam, got the steel studs up already, hard to bring them down. One question i need to ask though. I have a couple of storage rooms that have finished walls, but the floor is not finished - painted concrete. They are separated from the main area by dry walls I am rebuilding. If I insulate and finish the main area, what should I do with the storage rooms? I have no need in a laminated or ceramic floor there - do I have to seal the floor there as well so all the work to seal the main are is not a waste? Sorry, I am new to this

  • I think you can just keep them painted. The real issue now is being sure you monitor the relative humidity and use a de-humidifier if the humidity levels are too high. You want to be in the 50% humidity range which is typically hard to do in a basement without some sort of conditioning.

• Todd,

  Thanks for the video...very helpful. Two questions, though.

  You wrote: "Foil faced has a higher R value but it doesn’t interact with concrete well (it will deteriorate)."

  I am looking at using Dow Thermax Sheathing to insulate my crawlspace. It is foil-faced on both sides, but Dow claims you should fasten/glue it directly to foundation walls. See here:

  http://msdssearch.dow.com/PublishedLiteratureDOWCOM/dh_037d/0901b8038037d7a0.pdf?filepath=styrofoam/pdfs/noreg/179-07259.pdf&fromPage=GetDoc

  So, just wondering now what kind of deterioration you have seen with it. Have you used Thermax as opposed to Styrofoam?

  Also, Dow and others mention leaving a termite-inspection strip of a few inches near the top of the foundation wall. That seems crazy in terms of insulation/vapor barrier. Seems like that would defeat the purpose of the vapor barrier. So, I'm not sure if I should follow Dow's advice. Any thoughts on that?

  Thanks again..

  • Jack - If you look at Step 1 they suggest a vapor retarder or layer of poly. That is sufficient to protect the foil facing from reacting with the concrete. Aluminum will have an oxidation reaction when in contact with concrete which eventually leads to the breakdown of that layer. It's not a huge issue but one that should be addressed.

    The insect strip is important in areas where Termites are present.