ZIP vs ZIP-R in Atlanta, GA
RockstarATL
| Posted in General Questions on
Hello.
Building a custom home in Atlanta, GA.
The builder is using ZIP sheathing with 2×4 framing with Rockwool insulation.
What I would like to know is should ZIP – R3 or 6 be used or regular ZIP sheathing without insulation is fine.
Thank you in advance.
JC
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Replies
“What I would like to know is should ZIP – R3 or 6 be used or regular ZIP sheathing without insulation is fine.”
It maybe me but I am not sure what you are proposing.
Upgrading to Zip+R and filling the wall with rockwool?
I would be surprised if Zip+R with rockwool was the lowest cost to build for its R value option.
In my market a few years ago I decided a 2x6 wall filled with damp spray cellulose regular Zip and 1-inch exterior foam. Note finding someone to install the exterior foam is often difficult as the framers think it is beneath them as do the siding subs.
If you can get a quote for the different options in terms of the number of dollars per square foot you can enter that data with the R values in a BEopt model and it will show you what gives you the best return on investment.
Walta
Similar experience as Walta.
My options were
2x4 advanced framing, filled with damp spray cellulose with Zip R sheathing
or
2x6 top & bottom plates, with 2x4 studs on 12" offset centers, with advanced framing, filled with damp spray cellulose with standard Zip Sheathing.
The 2x6 top & bottom plate with offset 2x4 studs was both the least expensive and highest R value option.
Thanks for the reply.
What I wanted to know is if I need to ZIP sheathing with R (either R-3 or R-6) or can I get by with just ZIP sheathing without insulation in a 2x4 construction (I will have Rockwool wall insulation) in Atlanta. Thanks.
" or can I get by with just ZIP sheathing without insulation in a 2x4 construction"
No, you cannot get by with no insulation in 2x4 or any other construction.
"I will have Rockwool wall insulation"
If you insulate your 2x4 wall cavities with Rockwool, your insulation R value will be similar to most new construction in the area. If you use Zip sheathing (uninsulated zip) as your exterior sheathing, and you properly tape & seal the zip, you will already be doing better than most new construction in the area.
Whether or not most 2x4 wall new construction in the area actually meets applicable codes in the Atlanta area, I am not sure.
Whether or not a 2x4 wall construction with the insulation limited to that in that 3.5" cavity is a good idea in the Atlanta area, I am sure it is not.
There is no indication extreme weather is going to abate. Atlanta area weather has reached records or near records for the last several consecutive days, and is expected to continue to do so for the next 5-7 days. If I were building a new house now, I would take every possible low cost opportunity to
1. Air Seal
2. Add insulation
In the past in Atlanta 2x6 construction has been more economical than 2x4 + exterior insulation. It also offers a very low cost method to eliminate much of the thermal bridging.
If you have already started with your 2x4 framing, I would suggest that at min you use ZipR sheathing to equal the width of a 2x6 wall, and thicker if you can. If you are building on a tight lot line right up to the setbacks in the city and have already framed, it might not be possible to pivot to a thicker exterior sheathing. But if that is not an issue, do it. You will recover the cost.
I apologize. I did not mean to say use ZIP sheathing without wall insulation in a 2x4 construction. I meant to say can I get by with using uninsulated ZIP sheathing in a 2x4 construction with Rockwool insulation.
I really appreciate your input. Thank you!
No one can really answer your question but you.
What is the lowest R value wall you are legally allowed to build in your location?
How long will you own the home?
What will the upgrade cost?
Why are you so set on getting rockwool insulation?
Are you willing to invest 20 hours of your time to build a computer model of your home and get your answers or are wild guesses a good enough answer for you?
Walt