insulating basement walls.

Post in 'The Green Room' started by ihookem, Jan 16, 2013.

  1. ihookem

    ihookem
    Expand Collapse
    Minister of Fire

    Joined:
    Jan 25, 2009
    Messages:
    660
    Likes Received:
    42
    Loc:
    Allenton, Wisconsin
    I built a 2200 sq. ft. ranch ans put 2" styrofoam on the outside of the block. Since I got 250 studs for free I decided to build the walls in the basement and cover them with 3/16" plywood I also got for free. After it was all done my basement went up 2 degrees. The joist box already had 3" closed cell foam anyway. I'm a bit disapointed it ony went up 2 degrees though. Just in case some want to do their basement walls this is what I got out of it in case anyone cares.
     
    Collapse Signature Expand Signature

    Helpful Sponsor Ads!





  2. begreen

    begreen
    Expand Collapse
    Mooderator
    Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    60,667
    Likes Received:
    7,677
    Loc:
    South Puget Sound, WA
    250 studs! Wow, that is quite a deal. When you say it went up 2 degrees, what do you mean? Is it unheated?
     
    Collapse Signature Expand Signature
  3. maple1

    maple1
    Expand Collapse
    Minister of Fire

    Joined:
    Sep 15, 2011
    Messages:
    6,447
    Likes Received:
    1,117
    Loc:
    Nova Scotia
    Did you insulate inside?
     
    Collapse Signature Expand Signature
  4. daveswoodhauler

    daveswoodhauler
    Expand Collapse
    Minister of Fire

    Joined:
    May 20, 2008
    Messages:
    1,847
    Likes Received:
    96
    Loc:
    Massachusetts
    Also, is the basement heated? The insulation is used to retain heat, it won't generate heat :)
     
    Collapse Signature Expand Signature
  5. lukem

    lukem
    Expand Collapse
    Minister of Fire

    Joined:
    Jan 12, 2010
    Messages:
    3,687
    Likes Received:
    1,518
    Loc:
    Indiana
    Exactly. If you have no intention of heating the basement, insulating it doesn't add a ton of value. It will still seek equilibrium with whatever ambient temp is on the other side of the insulation, but it will be at a much slower rate. I wouldn't be completely shocked if your basement stayed a few degrees colder when the outside temp rises. Insulating an unheated basement doesn't add a ton of value.
     
    Collapse Signature Expand Signature
  6. northernontario

    northernontario
    Expand Collapse
    Member

    Joined:
    Sep 28, 2010
    Messages:
    120
    Likes Received:
    10
    Loc:
    Ontario
    Something else to consider, the basement went up 2 degrees, but what about the upstairs temps and the fuel consumed to heat?
     
    Collapse Signature Expand Signature
  7. velvetfoot

    velvetfoot
    Expand Collapse
    Minister of Fire

    Joined:
    Dec 5, 2005
    Messages:
    8,878
    Likes Received:
    634
    Loc:
    Sand Lake, NY
    That's a huge, easy to heat area that some people would really love (me).
     
    Collapse Signature Expand Signature
  8. jdp1152

    jdp1152
    Expand Collapse
    Minister of Fire

    Joined:
    Oct 4, 2012
    Messages:
    782
    Likes Received:
    266
    Loc:
    Massachusetts
    If the sill is insulated as stated, likely not much as heat transfer down is negligible in the absence of draft. Energy auditors recommend putting your money/effort elsewhere rather than insulating the living space/basement barrier. The sill is a vastly different story. Uninsulated crawlspaces/garages/basements with exposure to cold temps/air leakage would prove beneficial.
     
    Collapse Signature Expand Signature
  9. ihookem

    ihookem
    Expand Collapse
    Minister of Fire

    Joined:
    Jan 25, 2009
    Messages:
    660
    Likes Received:
    42
    Loc:
    Allenton, Wisconsin
    It is unheated and I did insulate with R11 and some r 7.5 (1.5" ) pink foam. I though I'd get more than 2 degrees even if it's unheated. It is 2 degrees though and it feels much more comfortable too. Oh well 300 bucks of insulation isn't the end of the world and it is 2 degrees. Just thought I'd throw it out there for others for refernce in case other wanted to do it. It would have made more difference if there was no insulation on the outside. Also, to northern Ontario , I didn't notice a reduction in heat demand but the floor must be 2 degree warmer so it has to be reducing my btu needs some.
     
    Collapse Signature Expand Signature
  10. begreen

    begreen
    Expand Collapse
    Mooderator
    Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    60,667
    Likes Received:
    7,677
    Loc:
    South Puget Sound, WA
    I haven't found that to be quite true. Our insulated crawlspace (should be called a tallspace) stays at 63-60F, even if it's 20 outside. Earth floor with plastic on top.
     
    Collapse Signature Expand Signature
  11. ScotO

    ScotO
    Expand Collapse
    Guest

    does that plastic do a good job keeping the vapor down in there, BG?
     
  12. DickRussell

    DickRussell
    Expand Collapse
    Burning Hunk

    Joined:
    Mar 1, 2011
    Messages:
    170
    Likes Received:
    70
    Loc:
    central NH
    Insulating the basement walls is only part of the job. With no insulation under the slab, you still have a huge area in contact with typically cool ground. Then there is the matter of air infiltration, introducing cold air at some rate, however slowly.
     
    Collapse Signature Expand Signature
  13. begreen

    begreen
    Expand Collapse
    Mooderator
    Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    60,667
    Likes Received:
    7,677
    Loc:
    South Puget Sound, WA
    Yes, it's bone dry down there and every thing looks the same as it did 6 yrs ago when we put it down. I was a little skeptical because this is in a really damp climate. The end result has been better than I expected. We rarely get into the teens here. But it can happen and I was concerned about pipes freezing. A couple winters ago when we did get down to 13F, I had a digital remote thermometer down there and we never went below 60F. I have insulated panels for the crawl space vents that I remove in late spring when temps rise outdoors.
     
    Collapse Signature Expand Signature
    ScotO likes this.
  14. ScotO

    ScotO
    Expand Collapse
    Guest

    So you basically laid the plastic right down onto the dirt floor, correct? I have a crawlspace with some moisture issues and I'm looking for a temporary fix until I can get time to concrete it (I'd like to eventually put a 2" skim of concrete on it)
     
  15. begreen

    begreen
    Expand Collapse
    Mooderator
    Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    60,667
    Likes Received:
    7,677
    Loc:
    South Puget Sound, WA
    This is still a crawlspace, but with 3-4' headroom. The floor is covered with 6 mil plastic. If you don't have a vapor barrier I would definitely put one down. I believe it's required by code out here.
     
    Collapse Signature Expand Signature
    ScotO likes this.
  16. StuckInTheMuck

    StuckInTheMuck
    Expand Collapse
    Member

    Joined:
    Dec 6, 2011
    Messages:
    169
    Likes Received:
    39
    Loc:
    沖縄日本

    Saw this video today. It explains a lot of the intricacies about basement insulation. Don't know if it was already posted on hearth.com somewhere or not. Insulating basement walls/floor may not add too much value to the sale price of a house, but over time the investment will pay off with energy savings. Good work getting it done.
     
    Collapse Signature Expand Signature
  17. Laszlo

    Laszlo
    Expand Collapse
    Member

    Joined:
    Jan 19, 2013
    Messages:
    39
    Likes Received:
    10
    Loc:
    SE Pennsylvania
    Really informative, thanks! Just got a home energy assessment and the #1 recommendation for my house was to insulate and air seal my basement band joists. Nice to learn about all the possible moisture concerns before going ahead with it.
     
    Collapse Signature Expand Signature
  18. StuckInTheMuck

    StuckInTheMuck
    Expand Collapse
    Member

    Joined:
    Dec 6, 2011
    Messages:
    169
    Likes Received:
    39
    Loc:
    沖縄日本
    You're welcome.. good luck with your project!!
     
    Collapse Signature Expand Signature
  19. DickRussell

    DickRussell
    Expand Collapse
    Burning Hunk

    Joined:
    Mar 1, 2011
    Messages:
    170
    Likes Received:
    70
    Loc:
    central NH
    I sat through that 30 minute video and thought that in general it was quite good. My only comment regards his assertion that the concrete foundation had to be dry. As long as concrete is separated from moisture-sensitive building materials by strong vapor retarder layers and well air-sealed on the interior, it can remain moist without harm. The notion that interior insulation layers had to have some low level inward drying capability has been challenged here: http://www.greenbuildingadvisor.com/blogs/dept/musings/joe-lstiburek-discusses-basement-insulation-and-vapor-retarders. Reference to this was made in another GBA blog: http://www.greenbuildingadvisor.com/blogs/dept/musings/how-insulate-basement-wall.
     
    Collapse Signature Expand Signature
  20. Ehouse

    Ehouse
    Expand Collapse
    Minister of Fire

    Joined:
    Jul 22, 2011
    Messages:
    906
    Likes Received:
    256
    Loc:
    Upstate NY

    Yep, lay 6mil right on the dirt. Crawl down there in a couple mos. and see the moisture buildup on the underside. You should also have some venting at either end of the stem wall.
     
    Collapse Signature Expand Signature
    ScotO likes this.
  21. begreen

    begreen
    Expand Collapse
    Mooderator
    Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    60,667
    Likes Received:
    7,677
    Loc:
    South Puget Sound, WA
    Also, the assumption appeared to be that the footing would be sitting in wet soil. That is not the case with our footings, even though we live in a damp climate. Our house has generous overhangs and good draining soil which help to keep our crawlspace really dry.
     
    Collapse Signature Expand Signature

Share This Page