Does anyone know of any non-biased studies comparing the cost of modified framing techniques with that of SIP construction where the whole wall insulation values are similar?

There are numerous topics here regarding the best configuration of a modified stick framed wall assembly: 2x6 with exterior foam and strapping, 2x4 double wall, Larson truss walls, etc. A traditional stick framed wall is pretty inexpensive to build, but it is also not very energy efficient. Whereas a stick framed wall that has been modified to be more energy efficient has increased material and labor costs.

Assuming you are paying for labor, at what point is it just more cost effective to utilize SIP walls? I realize this is somewhat a loaded question because of the variability of labor costs and SIPs material costs in different locations. But, I would like to see some hard data if it is available.

Thanks for your input.

I think what you'll find is that it varies quite a bit from one region to another. I really wanted to build with SIPs when we built, but the cost was too high. We have one builder that I know of who specializes in SIP construction, & was extremely expensive. There are some suppliers that cut panels to your plans, but don't do the construction. One of the reported cost savings is reduced labor costs because they go up quicker - but in talking with my builder, he was very reluctant to budget any less for labor because he wasn't familiar with the product. I'm willing to bed that if we had gone that route, it would have taken him longer than a crew that is experienced with SIPs.

So that was the long-winded answer. The short answer is, I don't think you're going to find a completely unbiased study. The other thing that I ran into when trying to compare was to get a breakdown was the labor vs. materials & interior vs. exterior framing. Even with SIPs, you need a crew to frame up interior walls. No one was able to give me numbers in terms of "this is what we charge for labor for exterior framing & here's what we charge for framing interior walls". Also, roof framing may or may not be SIP. There are so many variables, unless you find someone well-versed in both & is willing to give you the unbiased numbers, it's tough..

I don't know if they qualify as "unbiased," but the Building Science Corp. guys have a nice qualitative comparison of different high R-value wall construction types, in which they include costs (and other aspects) on a scale of 1-5:

http://www.buildingscience.com/docu...assemblies

Lee Dodge
http://www.residentialenergylaboratory.com
in a net-zero source energy modified production house

Lee thanks for the link to the Building Science page. Lots of information there and I like how they have a scale for different aspects of the wall assemblies. But I can’t say that I agree with some of their numbers as there seem to be some inconsistencies.

There are wall systems with lower whole wall values that have a higher thermal control numbers and there also seems to be some inconsistencies in the material use category. I am curious if labor is part of the cost or the buildability category. I am sure they good reasons for their numbers, I may just not have enough information to fully understand their reasoning.

Since there doesn’t seem to be anyone who can offer some hard numbers to compare just a shell (exterior walls, no roof), I may have to do some pricing and come up with my own estimates.

you can find some numbers here:

http://energetechs.com/wp-content/uploads/2009/12/Wall-assemblies-cost-analysis.pdf

SIP is not listed but I'm sure you can find some prices if you do a search in the SIP forum.

good luck
Adi

Thanks Adi, that appears to be good info and they breakdown how the numbers were generated.

Wall Construction                                   R-Value             Cost/S.F.       Cost/R-value/SF
Standard 2x6 @ 16" O.C.                        13.70                  3.72                 0.27
2x6 @ 16" O.C., 2" XPS                         25.00                  6.56                 0.26
2x8 staggered stud, 1.5" XPS                  30.00                  6.45                  0.22
Double 2x4 wall, 12" total thickness        36.50                  6.96                  0.19

By searching the web, I came across some numbers that appear to be an average, but no sure how accurate they really are.

6.5” SIP w/5.5” EPS                                21.00                  6.50                  0.31

This is with $4.25 per sq ft for material and $2.25 per sq ft for installation of SIP panels. I am assuming the $4.25 price is for SIPs is ready to install including all window and door cutouts. Also, the $2.25 per sq ft cost for installation seems a little high, but I did find similar numbers on several web sites.

So it seems that SIPs appear to be the higher cost in relation to R-value per sq ft. As far as energetechs 2x6 walls, it seems they could reduce the wall cost and improve energy efficiency by using 24” as opposed to 16” centers.

Anyone have any thoughts regarding these estimates – do they seem reasonable or not? I am a little surprised as I expected the labor savings on SIPs to be more dramatic.

john.... no numbers , just anecdotal.....
in 35 years of custom home building with a specialty in high insulation standards... i've often looked at sips... bit i could never see any savings vs. stick framing or cross'hatch... or double wall... we blow our own dens-pak cellulose

the one place i think sips excell in is in post and beam.... i have friends who build only post and beam and their standard is alway sips

i went to a net zero conference a couple weeks ago... and their experience was double wall..... either with 3" of spray foam and 9" of cells... or 12" of cells

they said their cost numbers never worked with sips

Kermit, thanks for your input. By looking at the cost per square foot numbers, it really seems that modified stick framing gives you a more efficient wall for the same or less money.

When I have gotten SIP quotes for past projects, they have just been too expensive and my customers have opted for framed or ICFs. That is actually why I built my own home with ICFs. I became a distributor after the fact.

It does look like double wall construction really gives you a lot of bang for your buck though. I am going to have to consider this for some future projects.

Thanks

John,

The numbers you posted really caught my eye. I'm doing owner-builder using metal polyiso foam SIPs. I'm certainly trying to save costs and the numbers you posted just made my day. I paid ~3.50/S.F. for metal Sips. Most were 6-inch (rated R49), however, I also used some 4-inch (rated R33) on a some shaded/interior walls. I stayed well under a $1/S.F. for labor and $1/S.F. for miscellaneous track, screws, connections, caulk. I used butyl caulk between every piece of track panel and foundation so my whole wall R-value should be better than any of the ones you posted. It appears the only wall assembly that cost less was the standard 2"x6". There has been a real learning curve to this such that I expect to knock off at least another $1/s.f. next time I use SIPs. I think there is far less competition and volume in the SIPs industry which results in higher prices than are necessarily justified. Their sales seem to depend on people believing in the system rather than being based on price. I don't think this has to be the case and I think SIPS will be more common once/if this changes.

Two observations:

The lowest cost per R/ft was the 12" thick wall.   A 12" wall will lose about 6% of your useable square feet.


After 30+ years of remodel, I have seen too many exterior walls with gaps at the top of the insulation where the insulation
sagged or compacted and left a gap.  I like having rigid insulation in the walls.

Thanks a lot sharing the wonderful information. Surely Your Experience Speaks....