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97 year old home in CT – Exterior Mineral Wool / insulation 2×4 / zip / rain screen / vapor questions please

Hedgehodge | Posted in Green Building Techniques on

Good Evening,

This all started from me trying to install a proper ledger board to finding rot to finding termite damage (oh gosh… so, so, bad) to finding out we had zero insulation in the house at all (oil heat and window ac units). I removed 2 layers of exterior siding (lead paint yay) and even the 3/4″-1″ lap boards used before sheathing (what a task). Then found out all my studs are randomly placed from 5″-23″ apart randomly (fun) and even fire-blocking (?) across it all, studs ending on the floor and only 1-4 studs per side go to the sill plate that was there at one point. I sprayed the back of my zip sheathing with borate / mold / fungus treatment and entire exterior stud wall and new sistered pieces 🙂 

I got it down to the studs, put in 2×4 mineral wool to each and every stud bay, nook and cranny and put up zip sheathing 7/16″. 

I plan on putting up the zip sheathing, then 1″ mineral wool, then coravent sv5 and 1×4 rain screen.  I suppose I’ll install James Hardie fiber cement (cheaper than vinyl – going for deep ocean blue hopefully 🙂 )

My questions now are: in regards to the windows that were already updated to double pane at one point before we bought the house and properly sealing them off and vapor barriers over the zip panels?

I have watched this ( ) and got some ideas but one of my windows has an inch behind the nailing flange and spray foam around it and others hardly are past the sheeting some how.

Should I put a vapor barrier over my Zip sheathing even if I’m taping it?

Do  I have to remove EVERY WINDOW and zip tape them or liquid flash them? These older windows seem odd to do, all videos i see are new builds. This may add many days to labor (i live on a mountain ledge so have hired help since its very unsafe (40 stairs to haul everything up plus its 2 story). the windows were installed into the old single pane / weight system window frames so I planned on doing ( 2:09 in the video) to bring it out past the exterior mineral wool and rain screen. I have 22 windows in this house thats only 1500 sq feet lol.

(dont be harsh please, working with lemons and short of jacking up entire house things needed sistered right away and the sill was a 4×6 that was completly eaten (been owner for last 6 years and wife just beat breast cancer after 2 years of chemo sooo all i wanted to do was make a nice deck outside for her and the kiddos now lol) (my windows im trying to seal correctly)

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  1. Expert Member


    As Voltaire said: Perfect is the enemy of the good. Do what you can, leave the windows if they represent too large a task. Fix what you see as priorities and move on from there.

    Taped zip works fine without an additional WRB, but you may find it a lot easier to detail things like flashing by adding one over the sheathing.

  2. Hedgehodge | | #2

    I just mainly dont want to have to come back and do it all over again :) I almost did vinyl siding a few months ago and kind of glad i didnt because there is no way I would have wanted to remove plaster and lathe inside the house with 2 kids. Lead, asbestos and a 5 year old thumb sucker still heh. I ASSUMED someone had insulated, I was wrong. Just want to do it right but within like 15k-17k which is pretty hard.

    Will these older windows will need to be completely reframed to do waterproofing properly, or would I be able to properly waterproof these easily?

    Also grip rite perm rating is 10.1 ASTM. I wont have any issues with trapping moisture and creating rot with mineral wool in the walls and on the exterior right...with that grip rite house wrap?.

    I agree with the quote too :)

    Thanks again

  3. Expert Member


    The problem is that when windows leak the damage is typically on the sill or lower jambs. So you can do a good job of integrating the new siding with the window frames, but without removing the windows to add a sill-pan and lining the opening, the framing is still vulnerable to moisture damage.

    1. Hedgehodge | | #4

      Darn it, thank you for info. That's what I was afraid of, cutting out that many windows, rehab on an older home feels.lile a ton more work than building a new home. Yeah, I wonder how far my Boracare +mold will get me if a little gets past if I spray it on backside of zips where all windows are. I'm hoping nothing gets past with good flashing and caulking , rain screen and the exterior wool though... But yeah.

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