More on Building Costs

Here are some construction cost numbers that can be found on the energetech web site. They also provide detail as to how these numbers were generated. I do think the cost of the 2x6 walls could be lower and the R-value higher if they used 24” centers.

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 SIPs 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.

It does seem that SIPs appear to be the higher cost in relation to R-value per sq ft.

One item that is not taken into account with these numbers is air infiltration. With proper installation, the SIPs walls should have a lower rate of air infiltration than the stick framed options. But the higher cost stick framed options should have very low air infiltration rates compared to standard construction.

So I am not sure there is a good answer in the information here. While most of the stick framed walls have higher R-values, they will probably suffer slightly higher air infiltration. And though the SIPs wall has a lower R-value, it would typically be considered a structurally stronger wall than the other options. If I find more or better information on this subject, I will post it.