Optimizing for SIPs

Here's the easy, one-step, starting guideline: Floor decking, drywall for finish and SIPs for the frame all come in increments of 4 feet, so both SIP and frame houses should be designed and built to fit with either 2-foot or 4-foot intervals in mind.

SIPs are by no means limited to boxy four-cornered rectangles. In fact, to date SIPs primarily have been used for building custom homes rather than within the affordable home market. Gabled dormers and complex rooflines are commonplace in SIP homes, many of which have been featured in expensive home parades sponsored by homebuilder associations and on the covers of glossy magazines. Yet those features tend to add moderately to cost.

To take full advantage of SIPs, the simpler the shape you draw up, the easier it is to build, the less waste material you'll have and the less labor you'll expend putting up the shell. This is as true for frame as for SIPs.

If your interest is cost optimization for the affordable housing market-an expanding market segment for SIPs-the University of Oregon's Center for Housing Innovation is the research arm with the longest track record to date. They've succeeded in incorporating a number of cost-cutting innovations with SIPs compared to standard frame. Contact them at http://darkwing.uoregon.edu/~esbl/Buildings.html#cascadia

Using SIPs in a standard pitched roof (6/12 or so) costs considerably more than building with conventional trusses and blown-in insulation. However, with optimized planning, the cost difference can be drastically lowered. Optimizing consists of enclosing additional living space on a second level. This can be accomplished by building short (5-foot or so) SIP walls along two sides of the upper level and placing roof panels at a moderate pitch (say, 6/12). Alternatively, you can eliminate the short walls but raise the SIP roof up to a full 12/12 pitch for a higher-volume loft space.

Installing SIP floor panels can make excellent economic sense where the home will be built on a pier-and-beam foundation. In this case, planning for wiring and mechanical systems needs more time and attention. Installing floor panels over a crawl space is a somewhat tougher call, based on long-term costs vs. energy savings.

Roof panels are not as cost-effective in shallow slope configurations , where roof trusses are often used;

... to create living space in otherwise useless attics, they add value.