Trouble brewing mid retrofit in zone 6A
Energy efficiency remodel on 1953 ranch house. 2×4 studs, no vapor barrier. Half way started, then abandoned. 2 exterior walls untouched, the others were stripped, airsealed, R13 mineral wool between the studs, covered with Zip sheathing system, one wall had the incorrect eps installed before work ceased.
Exterior insulation and rainscreens are far from the norm here in western South Dakota. I hired the only local company that was willing to take this on. Unfortunately products were substituted, crew didnt understand how tape gets lapped, air sealing would have been skipped had I not been able to jump in as needed, multiple things built up until the company I hired quit, which I view as a fortunate thing. Attempting to rehire this company is not something I’m willing to do. This completely wrecks my goal of two 1″ layers of unfaced EPS with offset seams taped; topped with a furred out rainscreen.
I’m left with one company who would do metal siding with a layer of metal faced insulation of R3 but no thicker, which is not sufficient R value to guarentee safety from mold due to condensation on my sheathing, which makes this not a option for me.
Or a second company that would tear down to studs a second time, and install hubers Zip-R sheathing. Which I dont fully understand it’s possible issues.
I read a article on GBA.com about a North Dakota site but I didnt grasp it’s full understanding. I have R 13 in my 2×4 walls which means I need a minimum of R 7.5 exterior insulation to be assured of mold free sheathing issues. But Zip R has its insulation on the interior side of its sheathing, correct? What issues would I face if I went this route? If I dont do the Zip R then I am out of options for additional insulation. I dont have the ability or the friends to call on to do the insulation & rainscreen ourselves before paying a siding crew to finish it off. Would Zip R 9 be a viable option or not? Any additional concerns or points this raises?
Thank you GBA for being such a great resource to call upon.
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Replies
Tia,
What is your goal? Do you budget constraints? I ask because ZIP R is a fairly expensive product, and there are other ways to improve a wall.
Also... What's going on in your attic? The biggest bang for the buck is often a combination of improved air sealing and increased insulation in the attic.
Hi Tia.
As Steve said, you should have many options for upgrading your walls. But I guess if you can't find a contractor to do the work, maybe not so much.
You are right to be concerned about condensation control and a wall with enough R-value of exterior insulation to keep the framing above the dew point temp is a durable wall. However, if you can't get a contractor to install that R-value of insulation, you can have less, you just need the appropriate interior vapor retarder.
I have spoken with a bunch of building scientists, architects, and high performance builders who have full confidence in ZIP R-sheathing when used right and acknowledging it's structural limitations of course.
You may find these articles helpful:
Walls that Work
Working with ZIP R-sheathing
Is adding insulation on the interior an option? Or are you intending to keep the existing interior finish (plaster?)
I wonder if you'd be better off finding some individual(s) as hourly hired help, and directing them yourself, rather than use an existing company with their own ways of doing things, the way they've always done them.
My father passed and left me some inheritance. My goals are to use this on my home. (all paid off, I intened to live here all my days and pass it onto my daughter) otherwise that money would slowly be spent on frivolous things. I've replaced the old hvac in my vented attic with a new 96% furnace and new ductwork in my finished basement (found two of my basement walls are leaning in, I'm talking with foundation reinforcing companies now. I'll be retrofitting foam board to basement interior) . I've done the attic myself with airsealing and insulating. Honestly I dont think hiring individuals will work out, I've never had any success with attempting this for any project as good hands are hard to find. I really wanted the exterior insulation instead of interior as our space is limited, especially in the bathroom and bedrooms on the main floor. Thank you all for your input, and thanks brian for the links on zip R. I'm thinking that zip r is my only hope for stopping the thermal bridging and getting my extra oomph in insulation. Additional question- I also was unable to find a company willing to insulate above roof sheathing (I'm due a new roof too!) I'll have to limp along with my 3" of insulation at the exterior top plates with r49 only near the center of my attic. (Sitebuilt truss gable roof) is there any thing I can do to limit thermal bridging up here at all even though I have to keep my insulation down on the ceiling ?
It would be less expensive to install 2" polyiso and separate sheathing than the ZIP product. Having installed both, I see no advantage, and several disadvantages of using the insulated Zip.
In addition the cost aspect of Zip-R, there are structural limitations involved. It does not work the same way as regular OSB or CDX sheathing. This is discussed in the link Brian Pontolilo included ("Working with Zip-R Sheathing"). You will want to involve a structural engineer, unless Huber has issued standard guidance that I am unaware of (I haven't worked with Zip-R since 2015).