Basement Insulation Help


  #1  
Old 03-10-13, 02:20 PM
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Basement Insulation Help

I'm seeking some help with insulating my basement before I put up drywall.

Here is some information about my house:
  • We live at the top of a large hill within my subdivision making water flow very good.
  • My basement currently does not have a sump pump installed.
  • I've walked around the basement numerous times and have never seen any water stains on the floor or on the wall.
  • During the winter months when felling the basement walls they feel very close to room temperature.
About my project:
  • I am leaving the ceilings exposed.
  • All framework and electrical is completed.
  • Most of my framing was pushed up against the basement exterior wall, making it difficult to get anything behind it. I recently discovered that I probably should have put up some form board before I put up the framed walls.
So as of now I was planning on using R13 or R15, but I'm not 100% sure since my basement doesn't really feel cold in the winter. So do I really need to insulate?

Here is a pic of my framing.
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What would you recommend to insulate my basement walls?

On another note I was also planning on using some R13 or R15 on my interior wall to help with sound deadening. Any other recommendations are welcome.
 
  #2  
Old 03-10-13, 05:33 PM
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Welcome to the forums! IF these walls are all below grade, you would not need any insulation at this point since the walls are geothermally correct, as you have determined. They will stay the same temperature year 'round. Too bad you didn't space the wall out, but that's spilled milk. It would have helped in allowing air to pass through the channel behind the walls and keep condensation to a minimum. Any foam board would have needed to have been put up prior to the wall being built and sealed at all joints with sealing tape. Again, milk.

If you have any part of the basement that is a walkout, you will need to insulate those walls with R13 or better yet, Roxul.
 
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Old 03-14-13, 06:47 PM
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You are in Zone 5, 6, or 7, check for closest city below the map: Chapter 11 - Energy Efficiency

You have your own state energy code, based off the 2009 IECC that requires R-10/13 or R-15/19, see footnote "c" in all exterior basement walls as a thermal barrier from the concrete wall (if not insulated): Chapter 4 - Residential Energy Efficiency


You will save money insulating below/above grade with a frost depth of 20-35" and average 3 monthly low temps of 24*F. StateGuidesUSA.com - Michigan - What are the average monthly temperatures in Michigan? Depending on where in MI, the groundwater temp is from 39-50*F during the year. Average Shallow GroundWater Temperatures | Ecosystems Research | US EPA Figure adding 10*F warmer for temps 6' below grade = 49-60* So the wall temp swings from 24* above grade and 2' down, with the rest of wall at 49-60* and indoor air at 70*, you will get condensation on the top concrete at 17%RH and bottom of wall at 42%RH in room air, without any foamboard. You need to weigh how much of the basement is below the frost line to have the temps "stable" at 50*F per your location; http://www.quadlock.com/technical_li...Insulation.pdf


No air gaps behind insulation, pumping warmer air to your rim joists, and leaving a gap for an outlet fire to run the wall length/height surfacing in the attic on the other end of the house due to not air sealing plumbing vent chases; MYTH: LEAVE AN AIR SPACE BEHIND THE INSULATION IN THE BASEMENT TO AVOID CONDENSATION.

And, it is against most all minimum building codes; Chapter 3 - Building Planning Check with local AHJ, especially about leaving the ceiling joists exposed; require 1/2" drywall per code. Keep up on your H.O.Insurance premiums...

Gary
 
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Old 03-14-13, 06:57 PM
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Gary, I think in the Myth situation the author was speaking of foam panels, and not batt insulation. The foam panels should be installed as he said with a complete troweled glue, along with taping of the joints. It makes no mention of fiberglas or mineral wool batts. If he inferred it, he was not correct, IMO.
 
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Old 03-14-13, 07:48 PM
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Thanks, Chandler, I'll remember that. Another one from NAIMA, convective loops form behind fiberglass and bring in more moisture in the moving air, pp.4, middle column;https://docs.google.com/viewer?a=v&q...fHFsk1RrK9G2HQ

Gary
 
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Old 03-14-13, 08:06 PM
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This one on pp. 45-47; http://www.buildingscienceconsulting...Measure_Up.pdf


The convective loop can be in a stairwell also; http://www.inspectapedia.com/Energy/...eat_Loss_3.pdf


Just can't win with any gap to a fibrous insulation; https://docs.google.com/viewer?a=v&q..._NGatSVo3wzmAQ


Correction, lol; Fig.7; BSI-009: New Light In Crawlspaces — Building Science Information

Gary
 
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Old 04-08-13, 03:52 PM
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Thank you for the responses.

So if I do decide to use bat insulation should I worry about condensation behind he wall, since I didn't put up any foam board?

I'm ok with putting up some r-13 if you guys feel that I need too. I'm was just worried about condensation.
 
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Old 04-08-13, 03:56 PM
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And if you think I should use insulation should I use faced or unfaced?
 
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Old 04-09-13, 03:47 PM
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You will get condensation with faced or unfaced f.g. or Roxul insulation if the concrete wall is cold enough and there is moisture in the room air. Asphalt paper facing is a vapor retarder, not a vapor barrier, not required in basements anymore; Chapter 6 - Wall Construction It is entirely up to you how to finish it. If you do0 remove the frame wall, shorten it to allow 1" foamboard under the bottom plate for an air/thermal/capillary break from the slab/earth; Pressure-Treated Sill Plates and the Building Code | GreenBuildingAdvisor.com

Compare the different wall insulation possibilities and their moisture risks;http://www.buildingscience.com/docum...study-analysis

Gary
 
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Old 04-23-13, 08:49 AM
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Not meaning to hijack this thread, but I'm in the exact same boat. Would it make sense to install XPS between the studs? Obviously, since the framing is already done, I can't do the whole wall end to end. I've read Gary's comparison above and I'm thinking about the spray on or the foam board/fiberglass bat options. Any suggestions?
 
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Old 04-23-13, 09:35 AM
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My appoligies for being late in this thread.
Here in Northern Ontario Canada, we generally (and I'll be doing this shortly), do studs away from the wall (an inch or more) studs with insulation (I use a batt for better R value and cost), then vapor barrior.
It should be noted (and stressed) that no wood should be directly touching the concrete (this will fail inspection in a second here). Instead, use pressure treated lumber (for anything touching the concrete), plastic, or other material between untreated lumber and the concrete (painted walls don't count).
Before doing any work, I'm going to do a simple moisture test so I know what I'm playing with. Taking an 18" x 18" sheet of clear vapor barrier, tape it against the floor (and another on the wall) using duct tape or tuck tape. Leave it over night (or longer).
If moisture appears under the plastic, you should make sure you have proper air flow between the walls (wood studs and concrete).

For spray foam... I'm personally on the fense. I don't have much personal experience with it and it is no cheap. If you can easily put foam board or insulation batt in place, go that direction. I'm considering using spray foam in the area above the concrete wall, between the joists in my basement. It's a lot of small spaces and has electrical and plumbing (hot water baseboards on the main floor) in many of them.
 
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Old 04-23-13, 06:27 PM
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Mike - Are you stressing not having the wood directly against the concrete due future mold concerns?
 
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Old 04-23-13, 09:21 PM
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Untreated wood in direct contact with concrete will rot - decompose. Mold may also appear.
 
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Old 04-24-13, 05:13 AM
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Nashkat1 nailed the issue on the head. Locally, it will 100% fail inspection.
I've seen roofing paper used between the wood and studs/strapping if they are directly attached to the concrete.
For the kickplates, I've seen either pressure treated lumber, plastic 2x4 (don't remember the exact name) used or standard wood 2x4, but with vapor barrier, roofing paper or even the pink pipe wrap material (again, memory failing on the correct product name).

Be sure to discuss with the local building inspector as their personal preference may come into play.
 
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Old 04-29-13, 05:58 PM
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Iowa is a much different climate than Canada. You don't want poly in a basement (especially above-grade) with your 1000+ Cooling Degree Days for summertime inward vapor drive for condensation collecting/running down the cavity side of your wall (compared to 50 CDD for Vancouver, BC.). I'd use some cavity foamboard after installing some Grace sticky wrap to the back of the studs, or fanfold (1/4") if room. Leave the f.b. loose to add canned foam for air-tightness; top/bottom/sides to framing. Builders paper is variable perms (5-30; moisture/water wicks through it), you can use it on walls (IMHO, no- as water is behind most walls), but not slab- need impermeable to meet code; #3 and #7; Chapter 3 - Building Planning
Use f.b. under the plate for a thermal/air/capillary break and no gap to insulation for resulting convective loops, degrading the cavity insulation (as post #5 link). Glue the foamboard in 1-2' square grid patterns as in post #3 link.

Gary
 
 

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