2x4 or2x6

[Robert_Flowers]

What is the better value for a wall?
7/16osb,2x4,r13 fiberglass,3/4 foam,1/2 sheetrock
                          OR
7/16osb,2x6,r19 fiberglass,1/2"sheetrock

Robert

[MikeT]

On my place, I opted for 2x6s at 16" o/c.  I also went with 1/2" CDX as opposed to OSB.  The reasons for both of these decisions were more for structural integrity and performance than energy efficiency.   I know some folks here are good at the R rating calculations, so I will leave that to them.

What factors do you want to consider when talking about value?

mt

[Willy]

2x6 would be cheaper than foam and you could also go 24" on center if you wanted to using them. I am using 2x6s on my cabin but going 16" on center so all the floor joists and ceiling rafters line up above and below them. Not that much savings changing the centers on a small cabin having windows and doors in the walls. Mark

[MikeT]

Here in the NW, the lumber costs seems to be dropping, but the costs for other things relating to building seem to be rising.

mt

[Willy]

Here in the NW, the lumber costs seems to be dropping, but the costs for other things relating to building seem to be rising.

mt

Yes wood is down that is why I want to get started on my cabin soon! I up/graded to 2x10s on the floor and ceiling for more strength(solid floors)and more room for insulation. I did not go to wider center which I could of cause it would have only saved a few boards. In the NW they are pretty stiff on insulation codes! Mark

[Robert_Flowers]

Sorry should have said all framing will be 16"o.c  what i'm thanking is 2x4 are $1.00 cheaper that would be about $200.00 plus the plates, headers,and door frames should offset the cost of the foam.
But would it be better energy efficiency than just r19 fiberglass?

Robert

[MikeT]

John R says that if you choose the foam on top of the 2x6s you can get an insulation level that is close to SIPs.

mt

[Redoverfarm]

It is really a personal preference as 2X4 vs 2X6 in regards to the insulation value, ease of framing, additional room to run plumbing and electrical. I think several example were given in an earlier post that there was not that much of a substantial savings. Personally I went for the 2X6 on my cabin room as I wanted to secure a loft partially down the wall heigth and I figured it was more substantial than 2X4.  There is one notable down side to use 2X6 in that the interior demensions of your rooms will be less(4" on wall to wall). But IMO not enough to bother me.

[MikeT]

With 2x4 studs (and if you are building to code and being inspected), you will need to be more exact with your holes for the wiring--and you will likely need to attach nail on plates over the face of the studs where the wiring runs.  If you are factoring in costs, gotta include that too.

mt

[MountainDon]

Maybe this'll help a little? To know for sure how it'll work out you'll need to run the numbers for your material lists and current ptices. I did this one a while back... year?

2x4 vs 2x6 wall framing, both 16" OC            

Calculations are based on a 14 x 26 ft cabin, 8 foot walls. One 36" wide door,               
three windows, one each 6x4, 4x4, 3x4. Framing includes  sill, all studs,                
two top plates.

Nails, sealants, etc. are NOT included. Actual doors and window               
costs are NOT included. Insulation quantities calculated with door and
window cutouts subtracted, and using area coverage pricing, rounded
up to nearest full package.            

                      2x4      2x6
Wall framing         $445       $510
            (2x6 14.5% more than 2x4)   

ADD fiberglass insulation=   $695       $810
                    (R13)      (R19)
            (2x6 is 16.5% more than 2x4)   

ADD 1" foam to exterior=   $960       $1,075
        R total=      (R18)      (R24)


Someplace I have the same comparison done with 24" spacing on the 2x6 walls.
Can't find it.   

[MountainDon]

As for R-value a 2x4 plus foam wall should have a higher overall R-value because the foam covers the studs. So the theory goes.

[firefox]

Don is absolutely right. Everyone thinks of wood as an insulator, and it is....but only for electricity,m
not heat. The wood studs act like a thermal short circuit and conduct the heat to the outside.

If you can put a shell of foam board on the outside of the framing, but obviously protected by the exterior
siding, etc. and get it as air tight as is practical, then you will be way ahead of the fiberglass batts.

Be absolutely anal about finding all the little cracks and crevaces that will leak air and seal them up tight.
This is also a lot easier to do when the foam panels are on the outside of the shell, since there will be less pipes, wiring to contend with. Adding fiberglass to the inside will help some, but getting rid of all the air leaks is by far the most important thing. Remember there is a top and a bottom to the shell.

Obviously you can blow all this hard work if you get bad windows or put too many in, but that should be obvious.

Bruce

[peternap]

Obviously you can blow all this hard work if you get bad windows or put too many in, but that should be obvious.



Boy...I wish my wife would get that through her head

[Willy]

Obviously you can blow all this hard work if you get bad windows or put too many in, but that should be obvious.



Boy...I wish my wife would get that through her head

I do not worry to much about a stud leaking heat on my home. Right now I have the wood stove burning down stairs and a window open all the way upstairs. It is cool to cold outside but we never close all the window unless it is 11 degrees out and blowing hard. It is still 70 degs in the house with 2x6 walls and R19 insulation in the walls, R48 in the ceiling and R38 in the floor. You loose most the heat in the ceiling so I would realy try to make it good there insted of tring to get a few more in a wall. I get a lot of heat out of my south facing wall from the sun warming the house so I don't want it insulated to good! Mark

[mvk]

Robert
FWIW
I think fiberglass batts don't perform very well and the less attention to air infiltration there is the worse they perform. I looked up your location, are you building around Macon, will this be a primary residence, are you going to air condition? Have you done any energy calculations? If you are heating with wood and have own supply and aren't air conditioning then it probably wont matter so much, as willy says. On the other hand if this is a primary residence and you are buying oil, gas, or electric for heat and air conditioning I think you are way under insulated ether way though I would use the 2x4 plus foam if I had to chose between the two. I agree with using the best windows you can afford and shading will sure help anywhere there is solar heat gain in summer.
Mike

[MountainDon]

What mvk said about air infiltration is extremely important. 

IF you are building in a code compliant area you MTL must add the requirements of the energy efficiency code into your cost calculations. Here in NM you have to run the floor, wall and ceiling insulation R-vlaues, the window and door u-factors, etc. through a calculator. You must submit a print out with the building permit application.

Certainly if your plan is to heat with your own grown and cut wood you may not be as concerned as if you were buying electricity, a fuel gas, fuel oil, etc. But on the other hand, the less wood you have to cut leaves more time for other things.

There is an online Energy Calculator. I have mentioned this before. That topic is found here.
OR a direct link to energycodes.gov/

The calculator is updated several times a year.

It is a useful tool even if all you use it for is to calculate the efficiency of various wall/floor/ceiling insulation, or how the u-factor of a cheap window compares to a low-e glass window.

[Willy]

What mvk said about air infiltration is extremely important. 

IF you are building in a code compliant area you MTL must add the requirements of the energy efficiency code into your cost calculations. Here in NM you have to run the floor, wall and ceiling insulation R-vlaues, the window and door u-factors, etc. through a calculator. You must submit a print out with the building permit application.

Certainly if your plan is to heat with your own grown and cut wood you may not be as concerned as if you were buying electricity, a fuel gas, fuel oil, etc. But on the other hand, the less wood you have to cut leaves more time for other things.

There is an online Energy Calculator. I have mentioned this before. That topic is found here.
OR a direct link to energycodes.gov/

The calculator is updated several times a year.

It is a useful tool even if all you use it for is to calculate the efficiency of various wall/floor/ceiling insulation, or how the u-factor of a cheap window compares to a low-e glass window.

I agree with you also. My windows are all Low E Glass, Tyvac on the outside walls, plastic vapor barier under the sheet rock, all sills, plates, corners, windows, electrical box openings for the wire ect are calked air tight. I only burn 3 1/2 to 4 cords of wood for a full years worth of heat. My winters are long and cold with lots of wind to! I have neibors that burn 10-12 cords a year for a smaller home. Mark

[MountainDon]

Here is a screen shot from ResChek. These figures are for the cabin as presently planned. I've used a colder, more heating degree days, location than where the cabin actually is as there are no locations that closer meet the conditions in my area of the Jemez. So we're probably over insulated; but that's  .

[Redoverfarm]

Willy did you use faced fiberglass bats or insulation in your walls or was it unfaced. I had heard that if you use faced then you shouldn't use another moisture barrier on the interior as mosture will get trapped between the two and mold will develope. Mine was unfaced (cheaper) then plastic vapor barrier on the interior.

[Willy]

Willy did you use faced fiberglass bats or insulation in your walls or was it unfaced. I had heard that if you use faced then you shouldn't use another moisture barrier on the interior as mosture will get trapped between the two and mold will develope. Mine was unfaced (cheaper) then plastic vapor barrier on the interior.

They used faced on the walls and the plastic was put right against it. That is what the inspector wanted and they approved the insulation. I had a company put it in. The cost was realy cheaper than I could buy it back then. They only wanted $895.00 to do the job. Now they get 3+times that! I used PVA Primer on the ceiling to seal it off since my attic was blown in 2 ft deep. Mark

[mvk]

Willy what type of blown in did you use and how did you like it? I'm surprised that the inspector like faced with poly! technically that's wrong? I'm not surprised that the insulators used it, it always seemed to be cheaper then unfaced and was easier to install, the better contractors would slash the facing if they installed plastic. Unfaced needs the bays to be just right to get a tight fit and that is where I think the trouble with batts lies, any voids and you got trouble. I have opened many walls with water damage even with seemingly intact vapor barriers. In winter you would have frost and wet frozen insulation inside walls. I switched to vapor barrier paint also, because I thought that it was almost impossible to install plastic with out some kind of holes, also at the time there were people saying that one nail hole would let in a quart of water or something like that. I wasn't completely sold on the vapor barrier paint either even with gasket-ed dry wall and plates. You had to have it mudded all the way to the floor and apply the paint before baseboard, window trim I thought. Just let to much room for error and if you didn't do it your self you had to depend on the integrity of some one else. That's why I liked foam as far as sealing for infiltration. I'm just not sold on it being out side that was always considered wrong back when I was studying this stuff. Being outside though is what makes it easy to get air tight. John has posted about vapor barriers and it sure seems to make sense!

I have been reading about people using dense pack cellulose with Larsen trusses and no vapor barrier? suppose-ably the cellulose can take up and let go of a lot of water with out any damage? There are some people over Vermont way doing this, anybody have any info on this I saw it on the Fine Home Building site but let my membership expire, I had to much trouble using the site! Luddite me. Anybody use Bib's or that new spider insulation, think glen posted about that.

Hey Don does your energy calculator mention (OK Glen here's another fat one) the crack factor?

Mike 

[Garrett In Tahoe]

I really think that if your concerned about the R value of your walls then 2x6 is the way to go. You can get high density R21 batts for 2x6 or R15 for 2x4, the additional cost is minimal. Faced batts allow for a better installation plus gives a bit of a vaper barrier. Don't use a visqueen barrier on the interior of the wall, it will trap moisture in the wall cavity as mentioned previously. The wall needs to breath, since the heat inside vs the cold outside causes condensation, like a glass of cold water. R values of rigid insulation are around R7 per inch of thickness. The problem with sheeting the exterior walls with rigid insulation is fastening your siding and windows. The windows would require a wood ground the thickness of the insulation as well as the doors. for solid nailing. Applying siding and trims over an inch of insulation will also require longer nails, and you will lose shear strength of the nail. The cost of 2x6 vs 2x4 is minimal, and labor is insignificant between the two. As mentioned before any waste lines that are horizontal in the wall will destroy a 2x4. If your in a very cold region your water supplies should not be in the exterior walls to prevent freezing. They should come up through the floor inside the structure in front of the wall. Your floor really has little heat loss since heat rises. Normally R19 is adequate for the floor, put your money in the walls and ceiling. Use operable foundation vents that can be closed in the winter to keep your crawl space warmer and to protect water lines from freezing. If you can afford it insulate your water lines in the crawlspace as well. Air infiltration is always a concern so the batt installation should be done leaving no voids. The inside perimeter of all your windows, doors, sill plates, and sill penetrations should be sealed with an expanding foam, but use one with low expansion properties. There are other blanket type of insulations where the interior walls are netted and then insulation is blown in filling the wall cavities solid, but it gets pricey.

[Robert_Flowers]

Don thanks for the link ResChek trying to download now but i'm on dailup Hell so i wll let you know right now it saysEstimated time left 4h55min!!!!

Mike
Are you building around Macon? yes about 25 miles east in Twiggs County
Will this be a primary residence? yes
Are you going to air condition? A big YES 100 plus with 99% humidly and no rain.
Have you done any energy calculations? Not yet
Heating with wood elec. backup
All windows will be double pane low-e,if we can find some flat land would pour a slab with pex but most of the land available i would need a crawlspace not to many basements around here.

Garrett
I was thanking about putting the foam on the inside of the 2x4 studs under the sheetrock,i read about the somewhere.

Robert

[Garrett In Tahoe]

Robert, Don't know why you couldn't but a few thing come to mind as potential problems.

1. You will need longer drywall nails or screws. They may have a tendancy to pop over time due to movement since it's not attached to a firm substrate.
2. Reduced shear value of nailing or screwing. Over time you may get settleing in the drywall at the walls.
3. Poor backing for the installation of cabinets and trim, again longer nails and screws.
4. Elec boxes harder to install out so far.

Personally I would not consider doing it that way.

[MountainDon]

The Building Science Consulting website has some very interesting methods of super insulating. They do not use a one size fits all approach. Rather, they've broken things down into, Very Cold Climate, Cold Climate, Mixed-Humid Climate & Hot-Humid Climate zones.

These links are direct to comparison plans/homes:
http://www.buildingscienceconsulting.com/designsthatwork/default.htm

http://www.buildingscienceconsulting.com/about/plans/default.htm