So I Just Added 2" Of Insulation To My Outside Walls... - Remodeling - DIY Chatroom Home Improvement Forum

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Old 12-30-2010, 10:03 AM   #1
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Location: Frankenmuth, MI, USA
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So I just added 2" of insulation to my outside walls...

and reading up on the Building Science website just confused the heck out of me compared to when I read it a couple of years ago. Things seem to have changed.

Executive Summary: Put up 2" of foam and siding. Did I screw up? See questions below


I live in Mid-Michigan and we're definitely a heating climate. I did quite a bit of research before starting this project and of course after executing it I now have doubts, regrets, and remorse so I thought, let me ask around to see if what I did was right.

I have a 1963 bi-level where the top 4' of the bottom level is above ground. The top level is cantilevered ~24" over the cement block foundation wall. The original walls of the upper level were as follows from inside to out:
  • 3 layers of latex paint/primer (Original paint in bad condition when we bought it and our two layers of primer and paint)
  • 1/2" Drywall
  • 2x4 studs
  • R-13 Fiberglass paper-faced batts
  • Asphalt Impregnated fiberboard (Celotex to be precise)
  • Fiberboard lap siding painted and sealed
  • About 2 million Asian Lady Beetle carcasses
  • Foil Faced foam sheets (1/4" or thinner)
  • Vinyl Siding (installed poorly. Whole sheet came off by unhooking the bottom and pulling)

Wife wanted new windows so it made sense at the time to replace the siding as well. After talking local inspector, it was determined I did not need a permit to replace windows or siding. We also talked about adding exterior foam insulation and he didn't see it being a problem as all the new construction around here is using it. Based on the Building Science website, it seemed like 2" XPS (Foamular 150 @ R-10) taped would be better than adding house wrap and putting the vinyl on top of it.

So the plan was:
  • Remove the existing layers of siding down to the celotex
  • Remove old windows
  • Fur out window openings to account for the 2" difference using 2x material
  • Install windows properly (Installed per manufacturer's instructions to the letter).
  • Put foam up and tape seams (glued with PL300 and 3" cap nails per manufacturers instructions. 3M 8067 tape to seal the seams as nobody carries Bild-R-Tape. The windows are taped to the foam using flash tape installed correctly).
  • Install vinyl siding over it using 4" galvanized roofing nails (which penetrated the studs by at least 1" by my calcs (1/2" celotex + 2" foam + 1/4" or so of vinyl siding lip = 1 1/4" into the stud. More than the 3/4" minimum required by the manufacturer and Vinyl Siding Institute).

And that is what we did. Now the doubts come into my head planted by neighbors and relatives.


1. Mosisture trapping. According to the BS website, 2" of XPS sealed and tape should be sufficient enough to prevent condensation on the warm side of the house. The fiberglass batts were installed poorly enough that it isn't a vapor barrier in any sense (holes, gaps, etc from the sections of drywall that were replaced). Issue?

2. Sagging. According to a relative, putting the siding that far out (2", the nails will sag over time. "Maybe not this year but they will sag". Thinking about this, the foam is holding the nail up. The foam is glued and nailed and isn't going anywhere. That + the fact that there are nails ever 16" into studs AND there is at least 1/3rd the nail in somewhat structural material makes this moot. Issue?

3. Things I may not have considered before executing this project?

Sorry for the length. I just wanted to get all the pertinent details out. I honestly think I am over thinking this and doubting my own work but I need a reality check here.


Last edited by muthian; 12-30-2010 at 10:04 AM. Reason: Typo
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Old 12-30-2010, 10:35 AM   #2
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sounds like you did a good job

i personally have never seen a sidewall moisture problem that couldn't be traced back to bulk water intrusion from missing flashing or a reverse lap or some other mechanically deficient problem

vinyl siding is not very heavy,if you nailed it the way you say,you will be ok


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