I was wondering if anyone might have a link to some information regarding the energy saved using SIP splines vs. standard stud splines to connect wall panels to one another. I am working on a project where we are working to have as little thermal bridging through the SIP building envelope as possible. We are also looking at alternative ways to make SIP wall/roof and SIP wall/slab connections that reduce or eliminate thermal bridging through wood studs. If anyone has information on this type of alternate SIP detail it would be appreciated. Thanks!

skyman111,

attached is the panel joint that we use that uses no spline and has soilid foam to foam contact

some companies can supply splines that are basically a thinner sips panel.  they are sheathing with foam breaking it that slips into the space replacing the solid 2x.  However some cases solid wood may be required for header supports, etc.

lzerarc,
Yes, that's the type of spline I'm thinking of for wall connections. My question, though, is regarding any actual numbers that I could provide to a client to show the difference in performance between using a thin SIP spline or using the standard wood stud splines. It's clear from some of the infared imaging that I've seen that using a SIP foam spline reduces thermal bridging compared with stud splines. But, I'm hoping to find some actual numbers that could be used to justify using the sip splines over studs.

cmkavala,
Thanks for the response. The SIPs we'll be using will have the standard OSB sheathing, though, not steel.

skyman;

sometimes the solid spline is required on OSB roof panels as a stiffner in order for them to make the span

Skyman ;

I too am intersted in this quantitave data.  The company I am dealing with use 2x lumber as splining material, while most use a ''mini-SIP' to join panels.  Moreover, some companies offer a cam-locking system to avoid even more thermalbridging so they claim.  Every claim made in accordance to thermal bridging is very logical, however I have not found a direct comparasion of both in the same real world conditions. 

I am sure that whole wall values could theoretically be determined with respective R-Values of all components forming the wall with a percentage value of each of these components.  I am sure that someone out there as already done these calculations.  One interesting product that can boost overall R-Value of a wall system is the use of insulated headers, see : http://www.pbssips.com/product-resources/headers-beams/.

Good luck with your research,

From a strictly theoretical perspective, wood has a thermal conductivity of 0.120 W/mK where EPS Foam is 0.033 W/mK. And assuming the worst case (most surface area for 2x splines) of 4x8 SIPS the 2x splines increase the thermal conductivity by 16.2%. For 24' wide panels, the splines increase the thermal conductivity by 9.5%. The wall is still exceptional insulation, but from a purely theoretical perspective, the splines do increase the thermal conductivity to an average of 0.0361 to 0.0383 W/mK.

Realistically speaking, one single dual-pane, low-e, argon filled (in other words very energy efficient) window will transfer much more thermal energy than all of the splines in the wall.

I too was very concerned about this issue, but the engineer did call out for some studs where I would have preferred splines. Now that I am done with the shell and finishing up the detailing I can appreciate some of the lumber, especially behind the cabinets. I know this does not address the technical side of your question, but a little thermal bridging might be worth the trade-off for a the extra structure.