# R13 to R21 wall upgrade



## Bud9051 (Nov 11, 2015)

Same story as before, what is the code minimum. From what I see r-20 is the minimum for the 2009 energy code. Personally, I don't see any builders in the north building with 2x4 framing, 2x6 is very standard.

Bud


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## 2Quiker (Dec 14, 2017)

Bud9051 said:


> Same story as before, what is the code minimum. From what I see r-20 is the minimum for the 2009 energy code. Personally, I don't see any builders in the north building with 2x4 framing, 2x6 is very standard.
> 
> Bud


I understand that r13 or 15 + R-5 insulated sheathing is code. But i am trying to figure out what would be a reasonable price to upgrade from wall insulation r13 batts to r21 batts.


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## jlhaslip (Dec 31, 2009)

Missing way too much information to be able to tell you with any degree of certainty.
The studs will cost more, allowing for approx 1 stud per Lineal foot of exterior wall is a decent guide number.
The insulation costs will depend on the difference in the price per bale and the number of square foot coverage per bale.
Nails will be about 50 percent increase. 2 nails per end of a 2 x 4 and 3 nails per end of 2 x 6.
It should not be much of an increase in Framing Labour. The same walls are being built, just will be a touch heavier to raise.
Doors and windows will cost very little more for the deeper walls.

Figure it out.


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## 2Quiker (Dec 14, 2017)

I am not trying to be a smart ass but i am not sure what you mean by more studds, nails etc. A 2x 6 wall has a dept of 5.5 inches, this R21 faced insulation has a thickness of 5.5 inches https://www.homedepot.com/p/Owens-C...Insulation-Batts-15-in-x-93-in-BF60/202585875.

So technically this R21 insulation should fit fine in the wall perfectly?


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## user_12345a (Nov 23, 2014)

You need 2x6 to do a 5.5" batt. 2x6 is really a little thinner than 2x4.

I would spend the extra money for 2x6 walls, because it's not something you can go back and ever change at a reasonable cost.

You can buy new windows in 25 years, you can change a furnace/ac/heatpump, you can air seal.

But you aren't going to spend tens of thousands of dollars adding insulation to the exterior of house once it's done.

Since you don't have gas available and are stuck with more expensive fuels, all the more reason to have R20+ walls. Yes, have them beef it up with the appropriate type of foam on the outside, adding an extra R5 to R10 and getting rid of thermal bridging.



In your other threads we were talking about performance of heatpumps; the house has to be well insulated to have a low enough thermal balance point to make dual fuel worth while. 

The way your builder wants to do your house, it'll perform the same as or worse as a house built 30 years ago in ontario canada - where i am. And you have expensive heating fuel and a cold climate.

These days the minimum is R24 exterior walls and 90%+ furnace with ecm motor. R20 basements and R50+ attics. Flex duct is not allowed. Your house would never be legal in most of Europe and Canada.

They were doing 2x4 with R11 (close enough) and 60 to 70% gas furnaces in the 1980s. R-1.8 to 2 windows.

Your codes are many years behind.

That 80% propane furnace they want to use with attic ductwork? The effective system efficiency will be 70% or much lower due to heat loss to the attic through the ducts.


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## mark sr (Jun 13, 2017)

> i am not sure what you mean by more studds, nails


A 2x4 stud requires 2 nails at the top plate and 2 at the bottom plate, a 2x6 requires 3 nails at each end where it attaches to the plates.


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## BIG Johnson (Apr 9, 2017)

jlhaslip said:


> Missing way too much information to be able to tell you with any degree of certainty.
> The studs will cost more, allowing for approx 1 stud per Lineal foot of exterior wall is a decent guide number.
> The insulation costs will depend on the difference in the price per bale and the number of square foot coverage per bale.
> Nails will be about 50 percent increase. 2 nails per end of a 2 x 4 and 3 nails per end of 2 x 6.
> ...


I actually prefer framing wit 6’s. The studs are usually better quality than 4’s, which means less time culling. Although I can carry more 4’s.


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## BIG Johnson (Apr 9, 2017)

mark sr said:


> A 2x4 stud requires 2 nails at the top plate and 2 at the bottom plate, a 2x6 requires 3 nails at each end where it attaches to the plates.


All the 2x4’s here are so twisted they usually take 4 or 5 nails to hold them straight. Occasionally I have to use an extra nail in a twisted 2x6.


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## chandler48 (Jun 5, 2017)

> So technically this R21 insulation should fit fine in the wall perfectly?


IT is odd that R21 is 5.5" thick and offers more insulation quality than comparable R19 which is 6.25" thick, and technically won't fit in a 5.5" space without compression, which is not recommended.


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## Bud9051 (Nov 11, 2015)

As if our construction materials weren't confusing enough with a 2x4 being 1.5 by 3.5 and so on, the insulation industry has to label r-19 as 6.25" when it is intended to be used in a 5.5" wall. Have they already accounted for that or do we calculate the r per inch (19 divided by 6.25 = R-3.04 per inch) and multiply by 5.5 for r-16.7? It is supposed to fit a 5.5" wall and it is supposed to be R-19, Hmmmm.

To help answer that question I found this chart:
http://www2.owenscorning.com/literature/pdfs/10017857%20Building%20Insul%20Compressed%20R-Value%20Chart%20Tech%20Bulletin.pdf

From the chart, insulation labeled r-19 and 6.25 inches thick will result in an r-18 value when installed in a 5.5" cavity. A little more calculating and that is 18 divided by 5.5" and we get r= 3.27 per inch, that is up from the r= 3.04 calculated at the 6.25" depth.

Conclusion, the r value per inch increases under a bit of compression while the total depth decreases.

I'm sure they have an explanation for why they like to mess with our numbers, so far I haven't run into it.

Note, remember, most of us have some experience with these insulations and their numbers and still it is confusing. So how does the average home owner deal with this?

Bud


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## user_12345a (Nov 23, 2014)

The way the batts are engineered/made has changed.

The R-21s likely are done in a way that traps more air. the air is the real insulator, the fiberglass "holds" the air in place.


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## 2Quiker (Dec 14, 2017)

I asked the bilders representative to verify what wall R value insulation they use on walls because R13 seemed very low now and days, not that i am an insulation/builder expert. The project manager called me and said they put R19, with sheetrock, outer sheathing the walls R value turns to 21. I still asked them to quote me for the R21.


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## user_12345a (Nov 23, 2014)

So it's a 2x6 house then?

you won't notice a big difference between R19 and R21. 

The effective r-value is well under the rating because the studs cause thermal bridging and you also have air movement.


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## Bud9051 (Nov 11, 2015)

Building codes specify "cavity insulation" and do not include drywall or sheathing as part of the total value. They assume those layers are there. So, your builder cannot use the R-21 calculation to meet codes. He can however install R-21 fiberglass intended to fit those 2x6 walls. My guess is he should not be quoting prices for insulation levels that are not permitted.

Have you determined what codes they are supposed to be following? Simply call the building department in your desired area and ask. According to this link it looks like the 2012 IECC (International Energy Conservation Codes) apply but every town has the final say.
https://www.energycodes.gov/adoption/states/idaho

Bud


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## user_12345a (Nov 23, 2014)

the builder probably knows what to do to reach minimum code levels. u don't have to worry too much.


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## Nealtw (Jun 22, 2017)

Our code calls for 2x6 for exterior walls.


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## 2Quiker (Dec 14, 2017)

user_12345a said:


> So it's a 2x6 house then?
> 
> you won't notice a big difference between R19 and R21.
> 
> The effective r-value is well under the rating because the studs cause thermal bridging and you also have air movement.


yes 2x6 walls.


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## ront02769 (Nov 28, 2008)

Where I am two bye six walls are required regardless of what goes inside. Ron


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## 2Quiker (Dec 14, 2017)

builder wants $1200 to upgrade from R19 to R21. Not sure if i will be able to tell if i would be more comfortable with just 2 R-values difference for $1200. based on the insulation upgrade cost savings calculator by build it solar i would see payback in over 10 years, save $53 a year.


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## Bud9051 (Nov 11, 2015)

I guess you have lost me 2Quicker. We started out with 2x4 walls and r-13 which seriously does not meet building codes and now he is supposedly looking for $1,200 more for this small upgrade, which I already explained may already be required. If code is r-20 he cannot meet that with r-19, code applies to cavity only. Find out what your local code officer wants and go from there.

As far as adding more insulation to improve comfort it was already posted you will not feel the difference. As for return on investment there are many other places you should be far more worried about that will have a quicker return on your cost.

Make the builder give you a quote based upon what the inspector will accept as minimum. Then you can put that $1,200 any place you want.

Bud


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## user_12345a (Nov 23, 2014)

ya, that's not a big enough difference to improve comfort when you already have r-19. Probably a 1 to 3% savings on the heating bill. whether to do it or not, it's up to you, you're stuck with whatever wall insulation they put, can't go back.

there is confusion with respect to codes and even the type of construction. like if it's on a slab or basement, if air ducts are going in the attic or what?


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## 2Quiker (Dec 14, 2017)

Sorry everyone. the house will be 2x6 walls. When i asked the builders rep about what type of insulation is used in the walls they told me R13 so that's why i asked about R13 to R21. After reading some energy codes i realized that wasn't right so i ask to verify with the building manager and they said they use R19 insulation. 

I am having the builder move the furnace form the attic to the garage, ducts works will be in crawl space. Going with a Carrier comfort 59scd 95% Gas/propane and upgrading the windows from .35 to .28 u-factor.


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## user_12345a (Nov 23, 2014)

Very good.

I hope they're doing your crawlspace as a mini-basement, with a concrete floor, insulated walls.

Doing it ventilated with insulation in the floor isn't as good, results in more energy loss especially with ducts down there.


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