SIP Panels -- Pros and Cons
Here is a recent question we were asked:
"Hi, I've got a question - it looks like you guys prefer stick-building the walls and ceilings for the timber frame and post & beam designs rather than using SIPs. I'm wondering why that is since it seems that SIPs are "all the rage" these days. The property we're building on is in a very high-wind area on the upper hillside in Anchorage, Alaska, so we're pretty concerned with maximizing our insulative potential!"
The Log Connection takes great care to ensure that our homes are handcrafted with the best techniques for ensuring a weather tight seal and structural integrity. The SIP panel (Structural Insulated Panel) system works very well in some applications and for some people.... but not everyone. A large part of the decision is understanding all of the pros and cons of the product and making sure they work for your design. We have outlined a number of areas that we review and discuss with our clients when making the decision of conventional framing versus SIP panels.
It is our opinion that the the use of SIP panels on the roof system is an efficient way to install a roof system quickly. The more simple the roof line, the more practical the application. In most situations, the panels can be made to easily span between our roof logs and be completely roofed in just days. The thicker the panel, the higher the R-value. If made the same thickness as a conventional roof, the R-value achieved is greater by about 30% or more, depending on the manufacturer. The panels are pre-cut at the assembly plant so the on site waste and clean up is lower with the use of the SIPs.
Most of our home owners are as interested in the look of their home as they are in the efficiency of the products. One of the largest issues our home owners have is the accent lighing you see in the ceiling of nearly all our homes...it is not yet possible to install a recessed or pot light into a SIP panel. Also, in areas with heavy snow loads the design of long overhangs will be limited to the strength of the panel.
The wall systems stand and install quickly on our post and beam homes and the upper gable ends of the stacked log packages. The pre-cut panels* are ready to install when delivered to the job site. Openings are pre-cut for window and doors, and minimal framing or trim work should be required. The on site waste and clean up is lower with the use of the SIPs.
The largest issue we have with the wall panels is that the exterior sheathing of the the panel is cut flush to the edge. We have a system that allows the exterior sheathing and interior drywall to EXTEND INTO the posts. This creates an impenetrable weather seal and no drafts at the joint. When butting a SIP up against the post there will eventually need to be a weather block/ trim installed to stop the draft. Hanging small pictures will be fine, but heavy artwork and shelving may not be possible since there are no solid studs to fasten to. Installing unplanned electrical boxes is a huge hassle and requires cutting and patching of the panels. Pre-plan and you will be fine.
* Rarely will the SIP manufactures visit the job site to acquire and verify the "as built" measurements. Therefore they will not assume any responsibility if the as built conditions are not 100% CADD perfect.
To sum it all up, the SIP panel is a great product when used with the right conditions with reasonable expectations. We encourage the conventional stick build system for our stacked log, and the post & beam homes. The SIP panel is recommended for our timber frame homes.