structurally integrated panels
From: Kay Argyle (
Date: Fri, 1 Feb 2008 16:18:27 -0800 (PST)
Sorry for a late response. This got lost in my "drafts" folder ...

> Have any communities used or are any communities planning to use SIPs in
> their structures. It would seem to have many advantages (well insulated,
> rapid construction, precision and accuracy, sound attenuation) and at
> one disadvantage (formaldehyde emissions).

Wasatch Commons (SLC, Utah) was built using R-Control brand structurally
insulated panels (SIPs), cut to the architect's specifications at the
factory, trucked to our location, and assembled.  They consist of a 6"(?)
foam core, like fine-grained styrofoam, sandwiched between strandboard.
Apparently the foam contains boron for pest control - you really do not want
to handle broken pieces and then touch your eyes (as I found out the hard
way).  I didn't notice any offgassing smells from the panels, even during

We have natural stucco outside the SIPs.  Interior walls are stud
construction, with offset studs and batting between attached townhouses.

Insulation is excellent. During the summer our downstairs is typically about
15 degrees cooler than outside.  We have a lot of windows, so any advantage
in sound attenuation isn't that noticeable.

I do recommend offset studs! We can occasionally hear the neighbors' music
or washing machine, but only faintly - a vast improvement over the usual
attached unit. I wish the architect had had the sense to use offset studs or
other soundproofing for walls within the units as well - as one resident put
it, if she sneezed in the kitchen, her husband said gesundheit from the
bedroom, on the opposite end of the unit.

SIPs are more stable in earthquakes than stud construction (theoretically; I
hope not to be a test case) - a consideration in an area that has averaged a
magnitude 7 or higher approximately every 350 years for the last several
thousand (currently 250 years overdue :O).  On the other hand, our location
in the valley puts us in more danger from soil liquefaction or a seche wave
than from shaking.

The time benefits of SIP construction are greatest for long straight
stretches of wall, dropping 8x24-ft panels into place one after another.
Oops - Our architect liked corners. The exterior walls zigzag in and out,
and most are shorter than 24'.

The electrician's opinion of SIP construction was profane.  The foam has
open channels about two inches in diameter, horizontally at knee and chest
height, and vertically every six feet or so, for wires. Many places he had
to run multiple wires, and had a major struggle them all through that narrow
tube.  Pipes and ducts had to go through interior (stud) walls - except
downstairs has an floorplan, meaning every pipe, wire, duct, and cable for
the upstairs had to be fed through a single three-foot-long wall.

A serious shortcoming is strandboard's behavior when wet.  An error in
construction of the upstairs decks on half a dozen units resulted in water
running down inside the stucco.  We kept finding little crumbs on the floor
near a gap in the baseboards. Finally my roommate pulled off the drywall to
see what was going on (she was thinking insect infestation).  The
strandboard had rotted out, leaving only the foam to support the weight
above. Fortunately that was not a major load-bearing wall. Despite it being
well past the one-year warrantee on the construction, the architectural firm
and the contractor chose to take responsibility - thank heavens, otherwise
the community would have faced at least tens, possibly hundreds, of
thousands in repair costs, as it entailed ripping out and replacing entire
exterior walls.


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