Two Walls
Two Walls
I am looking at two walls and your input.
My Goal is to have a more energy efficient home, but at the same time be reasonable in my approach. Meaning it does not need to meet passive house standards nor am I looking for any types of certifications.
This is my first time as a owner builder with some building experiences to do this type of home.I have been looking to find the right subcontractors to achieve my goals and have found some.
I hope you will be upfront with your insights.
We have purchased two acres in which We can build two homes. For now we are going to build the 700 square foot guest home first which we will live in.
Thanks ahead of time for your responses
Richard
Generally Info
20×35 Home 700 square feet.
Zone 4 High Desert 4,900 feet central Arizona.
2 Bedroom 1 Bath
6 Windows, 2 Doors (of these 3 Windows and 1 Glass Door will be on the South Side Of House.)
Windows by Wasco (Genio High Performance Windows u value .17)
All Electric Home.
HVAC- ERV Ultimate Air ER80, Mitsubishi MZ-FH09NA 9,000 BTU 30.5 SEER Ductless Mini Split.
Slab on Grade.
Primary Air Barrier inside wall and ceiling plane.
7/12 Pitch Metal Vented Roof. 2 Foot Overhangs.
Energy Heel Trusses. Simple Gable Roof/Blown in Knauf Ecofill above ceiling plane insulation R-45
Design Criteria For The Area We Are Building.
Winter Design Temperature 20 Degrees
Wind Speed 90 MPH
Seismic Category C
Common Feature For Both Walls.
2×6 Advance Framing, 24 inch on center.
Knauf Ecofill BIB R-23
475 Intello Plus. Airtightness, smart vapor control, and dense-pack reinforcement all in one.
Drywall.
Wall A
Zip R Sheathing, 1 inch thick R value 3.6
Questions
1. From my understanding a r value of 3 is a adequate thermal break for zone 4. Is this true?
2. Is there a benefit of adding a liquid applied joint and seam filler where the zip R panels meet? From my understanding there is a 1/8 inch gap of the OSB to the insulated foam. The foam butts up to each other not the OSB aspect of the sheathing.
3. Cold sheathing on the exterior should that be a concern for my climate and wall insulation thickness?
4. Placing a rain screen over the Zip R sheathing i.e. Furring Strips for sidings. If I choose to use vinyl siding I cannot use furring strips. There is a product called Glide Lock Siding Hanger Installation System which will allow me to place the vinyl siding directly onto the sheathing. If I used vinyl siding is their a thin blanket type rain screen that could be used or is this not needed?
5. As a newer product that does not have much history is there any concerns that maybe I should be aware of.
What I Like about zip r sheathing
1 product 3 functions sheathing, continues exterior insulation, WRB.
Reduced Labor and ease of installation.
Seems I do not need to make extension bucks for Windows and doors.
Wall B
Zip Sheathing with some form of exterior rigid insulation added.
Questions
Option A
1. Depending on the answer from above if a R value of 3 can serve as a thermal break for zone 4. I understand it is still best to go a minimum of 1 inch of exterior rigid insulation over the sheathing is this true? I believe this deals with the dew point.
2. From everything i have seen best practices is to place a rain screen over the exterior rigid I nsulation then add siding?
This wall assemble seems to require more labor and require more detailing around Windows and doors.
Option B
1. Insulated Back Vinyl Siding. Their are insulated back vinyl sidings that have a r value of three and four. Has anyone had any experience of this insulated siding material over zip sheathing?
2. As mentioned above, there is a product called GlideLock Siding Hanger Installation System that allows me to attach the Vinyl siding 24 inches on center. Has anyone used this system. Vinyl siding needs to be flush to sheathing substrate.
This option can reduce labor assemble combing the siding and thermal break insulation in one step.
Is there any other questions I should have asked and didn’t?
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Replies
Richard,
Q. "From my understanding, an R-value of 3 is a adequate thermal break for Zone 4. Is this true?"
A. Not really. There is no particular definition for what can be called a "thermal break." It is certainly true that there is no minimum R-value for exterior rigid foam in your climate zone -- for more information on this issue, see Calculating the Minimum Thickness of Rigid Foam Sheathing.
When it comes to a thermal break, R-3 is better than R-2, but worse than R-4.
Q. "Is there a benefit of adding a liquid applied joint and seam filler where the Zip R panels meet?"
A. No. You should follow the manufacturer's instructions concerning the installation of Zip-R sheathing. The manufacturer requires the use of Zip System tape at the panel seams.
Q. "Cold sheathing on the exterior: should that be a concern for my climate and wall insulation thickness?"
A. In Zone 4, you aren't likely to have moisture accumulation problems or sheathing rot problems.
Q. "Placing a rainscreen over the Zip R sheathing, i.e. furring strips for siding: If I choose to use vinyl siding, I cannot use furring strips. There is a product called Glide Lock Siding Hanger Installation System which will allow me to place the vinyl siding directly onto the sheathing."
A. If you want to install the vinyl siding directly to the sheathing, you don't need a special "Glide Lock Sliding Hanger Installation System." Just nail the siding to the sheathing, following the siding manufacturer's instructions. Vinyl siding does not require a rainscreen, since it is inherently well ventilated and well drained.
Richard,
Q. "I understand it is still best to go a minimum of 1 inch of exterior rigid insulation over the sheathing. Is this true?"
A. Exterior rigid foam reduces thermal bridging through the studs, improves airtightness, and adds R-value to the wall system. But there is no minimum requirement.
Q. "I believe this deals with the dew point."
A. In some climate zones, that's true. But in Zone 4, it isn't necessary.
Q. "From everything i have seen, best practice is to place a rainscreen over the exterior rigid insulation, then add siding?"
A. That's true for many siding types, but not for vinyl siding. For more information, see All About Rainscreens.
Q. "Insulated Back Vinyl Siding: There are insulated back vinyl sidings that have a R-value of three and four. Has anyone had any experience of this insulated siding material over Zip sheathing?"
A. I don't recommend the use of insulated vinyl siding, since this type of siding modifies the siding in a way that removes the best feature of the siding: the fact that the bumpy profile of ordinary vinyl siding leaves a ventilated gap between the siding and the housewrap. Insulated vinyl siding has a flat back and no air space -- that's much worse than ordinary vinyl siding from a ventilation and moisture performance perspective.
Q. "There is a product called GlideLock Siding Hanger Installation System that allows me to attach the vinyl siding 24 inches on center. Has anyone used this system?"
A. I'm not familiar with it. I'm not sure what advantage it provides.
Thanks Martin Very Clear
You will have trouble finding people to install unfamiliar products correctly in the trades.
See
http://www.dupont.com/products-and-services/construction-materials/building-envelope-systems/videos/moisture-in-coated-sheathing.html
http://www.dupont.com/products-and-services/construction-materials/building-envelope-systems/videos/zip-reverse-shingling-vs-tyvek.html
http://www.dupont.com/products-and-services/construction-materials/building-envelope-systems/articles/wall-sheathing-comparison.html
With Intello on the interior you already have a class-II vapor retarder under wintertime conditions, mitigating any dew point issues, but that's already only a very small risk in zone 4B even without the Intello.
An alternative to a 2x6 /R20 wall (IRC 2015 code minimum), at the same wall thickness a 2x4 16/o.c. (25% framing fraction) wall with foam edge strips on the interior side will outperform 2x6 wall with a 20% framing fraction. See this bit o' bloggery:
https://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/making-case-exterior-foam-insulation
in particular this graphic:
https://www.greenbuildingadvisor.com/sites/default/files/2x6options_1_0.jpg
The Bonfiglioni wall is 2x4 wall with ~R4 edge strips fattening it out the same wall thickness as a 2x6 framed wall, and would be comparable in performance to (but cheaper than) a 1" ZIP-R 2x6 wall.
But as pointed out in the recent blog piece, optimizing the window size, type, & placement using BeOpt can be a far cheaper way to enhance overall performance than adding an inch of foam or foam-loaded vinyl siding. Focusing too closely on wall performance might miss bigger opportunities in the bigger picture.
Thanks Dana I will look at your suggestions
My first thought or question is.
Would I need exterior insulation outside the sheathing. In this case I would most likely use Zip standard sheathing material.
The cavity would be probably still be R-23 with Knauf Ecofill
Richard,
Q. "Would I need exterior insulation outside the sheathing?"
A. I've tried to explain this concept in my earlier comments, but I guess it's still unclear: In your climate zone, you don't need continuous exterior insulation. However, continuous exterior insulation is still desirable because it improves the thermal performance of your wall.
Thanks Martin
I guess my question was directed towards Dana's suggestion for a Bonfiglioni wall.
But I thank you for emphasizing my options.
This is a great source for builders who want to improve the performance of their homes and is very much appreciated.