I am looking to have new windows and siding installed at my home in Omaha NE(climate zone 5, and would also like to re-insulated as well. This is the process i am looking to do:

1. Remove and save siding/sheathing. (same thing on my home 3/4 plywood)
2. Remove old batt insulation.
3. Install plastic vapor vapor barrier against drywall between studs. (is this even necessary)
4. Install Roxul
5. Reinstall sheathing
6. block around windows with 1" nailers to make up for foam
7. Install 3/4" or 1" polyiso
8. Install windows and house wrap (need to figure out interier jamb extensions to make up for the foam)
9. Install siding

Please let me know if anything can be added/removed from this list.
Thanks-

Posted By DavidW on 21 Feb 2017 05:02 PM
I am looking to have new windows and siding installed at my home in Omaha NE(climate zone 5, and would also like to re-insulated as well. This is the process i am looking to do:

1. Remove and save siding/sheathing. (same thing on my home 3/4 plywood)
2. Remove old batt insulation.
3. Install plastic vapor vapor barrier against drywall between studs. (is this even necessary)
4. Install Roxul
5. Reinstall sheathing
6. block around windows with 1" nailers to make up for foam
7. Install 3/4" or 1" polyiso
8. Install windows and house wrap (need to figure out interier jamb extensions to make up for the foam)
9. Install siding

Please let me know if anything can be added/removed from this list.
Thanks-

With foil-faced foam on the exterior, do NOT install an interior side polyethylene vapor barrier, since any moisture that finds it way into the cavity can't leave quickly via vapor diffusion alone.

In zone 5, with as little as R5 of exterior foam you would meet the IRC prescriptives for being able to use interior latex paint, per Table R702.7.1 :

http://codes.iccsafe.org/app/book/content/2015-I-Codes/2015%20IRC%20HTML/Chapter%207.html

Polyiso needs to be derated a bit when it's on the cold side of the assembly, and R15 rock wool is going to need a bit more exterior R for dew point control than R13s, so 3/4" polyiso is out, but 1" (R6- derated to R5-R5.5 for dew point control in zone 5) should be fine.

While you have it open, take the time to caulk the wallboard to the studs inside every stud bay, seal the bottom plate to the subfloor, and seal the seam between any doubled up framing such as top plates, etc. using polyurethane caulk. (This goes pretty quickly if you invest in a powered caulking gun). Seal up all the electrical boxes electrical & plumbing penetrations of the framing & wallboard too. Some of this will be easier to do with can-foam than caulk. A square inch of air leakage into the cavity from the interior moves a heluva lot more moisture out to the sheathing in winter than vapor diffusion through latex paint on wallboard.

Trim the fit of the batts perfectly, no compressions, no voids, or it will not perform to it's rated R due to thermal bypass air currents/convection or the lower R of thin sections. A 10" bread knife works great for sculpting batts, but so do purpose-made batt knives.

Tape/caulk the seams of the new sheathing with the appropriate materials. (Polurethane caulk between the framing & sheathing on each sheet as it goes up works, but so does taping the seams and caulking the top & bottom edges.)

A critical factor to get right with the housewrap is to lap the window flashing properly to the housewrap. Unless you're replacing the windows this means the housewrap will probably have to go between the sheathing and foam layer, which is fine (a standard "innie" window mount where the glass is roughly co-planar with the sheathing rather than the siding.) When taking this approach it's better to use a crinkled rather than smooth housewrap (eg Tyvek DrainWrap), since it gives it a bit of capillary break, and a path for any bulk water to leave via gravity. The small amount of air leakage from that micro-gap isn't much of a thermal bypass, and will not measurably affect the the thermal performance of the asssembly.

thanks for the comments. on your last note, i will be replacing the windows at the same time as the rest of this project. Should I be able to have a 1" nailer to mount the windows to to make up for the foam and then wrap the windows in a standard method? Also, crinkled wrap would be normal Tyvek homewrap?

Standard housewrap is smooth & flat, which is fine if you're mounting the windows "outie", with the window flashing extending out past the foam, with the housewrap on the exterior side. Tyvek DrainWrap is NOT the most commonly used Tyvek product. It is a crinkled/crepe texture, rough on the surface, with enough space for water to drain down even when installed between rigid foam and sheathing. Lapping the window flashing properly to the housewrap is critical for keeping bulk water intrusions into the wall cavities bounded. How you mount the windows affects where in the stack-up the housewrap should go.

More: http://www.greenbuildingadvisor.com/blogs/dept/musings/innie-windows-or-outie-windows

http://www.dupont.com/products-and-services/construction-materials/building-envelope-systems/brands/water-barrier-systems/products/tyvek-drainwrap-moisture-barrier.html

I do plan on doing outie windows; using a 1" nailer so I don't need to try to mount the windows to the foam. On that note, can I nail the siding through the foam, or should I use furring strips?

Long-nailing through 1" foam works for some siding, not for others. Consult the manufacturer's installtation instructions. (Sometimes there are specific instructions for installing over foam.)

Using furring can still be a good idea though, since it creates a capillary break (no moisture can wick across even 1/8" of air), and an excellent drainage & drying path for wind-blown water that makes it past the siding.
If depth is an issue, strips of half-inch CDX or OSB thorugh-screwed to the studs 16" o.c. works, but may need ring-shank nails for the siding itself. Again, consult the manufacturer's literature.

One sure way to ruin the excellent expensive properties of mineral wool insulation is to surround it with foam, house wrap, and latex paint. GBA pushes alot of foam since it's sponsored to, is paid to, and that ill advise backed by little data has migrated to other "green" sites like this. Foam is not green since it does not bio-degrade, ends up in land fills polluting the environment as well.

There are a summary of foam properties I posted here, Dana 1 & GBA does not understand and used "vapor diffusion" incorrectly above, AND, there are many other properties to know: http://www.greenbuildingtalk.com/Forums/tabid/53/aff/14/aft/84342/afv/topic/Default.aspx

People that don't understand these properties try and make sense out of code data but, since code cannot account for specifics it is a poor source of data that most people make worse.

Mineral wool batts and rigid IS board is one of the best(structurally and hygrothermics) most expensive options so, if you surround it with the wrong boundary conditions like above it ruins it's properties.

If anyone wants to use MW batts look at OC thermalfiber too it may be cheaper batt than Roxul: http://www.thermafiber.com/home/about-thermafiber/

To maintain it's properties use MW outsulation board. It may be $.40-.60 SF more than foam but it has much better wet/dry properties than foam and much higher perm-inch & DWW/DWS.

Roxul split installation guide is good: http://www.roxul.com/files/RX-NA_EN/pdf/Technical%20Bulletins_Guides/Residential/13A76%20ROXUL%20COMFORTBOARD%20IS%20Installation%20Guide%20FINAL.pdf

If the siding (#1) is structural rate that satisfy's braced walls sheathing/membrane (#4/5) is not required. There are some better mods but I don't give those out for free, it is another talent to know when manufactures are adding layers to protect warranty vs produce good assemblies (eg: #7). 1/8" gap Dana 1 is way too large to get the proper CFM/ACH. Fiberglass faced, PCM, or some MAG wall boards are far better to enhance MW properties and breathability. One also has to know the best air seal methodologies but that would take a holistic design approach not defined in code either and there is not enough design info here to provide. 

The most critical are the surface layers, whether a paint is CL 1-2-3 if you can even find accurate mfg data is only part of the equation.