Not all construction techniques created equal
SIPS are easy to put up and save energy costs
Sometimes the best ways to build don’t automatically become mainstream as quickly as they deserve to, and wall construction options for new homes and additions are a case in point. While most house walls these days are still built following ideas going back to the 1950s, a building option called structural insulated panels (SIPs) are one option that’s entirely different.
Depending on how you build with them, SIPs can save a surprising amount in heating and cooling, while adding only minimally to overall construction costs. And while recent changes to building code requirements don’t mandate any one wall-building approach exclusively, new code standards are certainly making SIPs more sensible with cost-conscious, qualityminded builders and homeowners.
To understand why this evolution is unfolding, you need to know exactly how codes are changing.
Building codes are largely provin- cial matters, and over the last few years more demanding requirements have been appearing across the country. Sometimes called “E80” codes, the most significant of these changes is aimed at improving the energy efficiency of new houses. One key issue is the way E80 requirements now deem the old 2-by-6, R20 stud-frame wall obsolete. Depending on where you live, code minimum for walls may be R22 or even R24, and this forces builders to create walls differently.
Made by a handful of companies, SIPs take the place of exterior studframe walls and even roof trusses, delivering structural strength, insulation and vapour barrier all in one. I’ve built with SIPs several times since 2003 and they go up quickly and easily. Depending on how you build, SIPs can mean 30 to 50 per cent less energy consumption than standard wood-frame wall construction of the same R value, with building costs only 2 to 3 per cent higher. Alternatively, SIPs can also offer lower wall construction costs while delivering the same energy performance as the highest new code requirements of R24. A study by Brock University professor Dr. Tony Shaw shows how. Shaw’s most recent work quantifies what many builders have sensed for a long time but couldn’t always put their finger on. Some types of insulation products keep homes measurably warmer in winter and cooler in summer than other types with the same R values. For example, using real-world analysis, Shaw has shown that an R17 SIPs wall delivers superior energy performance to R22 stud-frame, fibreinsulated walls, and equal performance to the same kind of R24 stud walls under typical winter temperatures of 3C to -10C. Material cost for R17 SIPs is the same as the R24 equivalent, but SIPs go up much faster, lowering building cost. The reasons behind energy disparities in insulation products with identical R values are easy to understand once they’re explained. Insulation products get their R ratings from lab tests where no air movement is allowed to occur through the insulation. In reality, however, air movement and con- vection is always a possibility within building structures.
Insulation products that allow air movement through them have lower energy performance than insulations with similar R values that do not allow air movement. Since SIPs get their insulating value from foam — that’s impervious to air movement — the R values determined in the lab are the same as those delivered in the field. SIPs also offer other advantages, like lower air infiltration within the structure, no chance of internal condensation and mould growth, and more reliable finished wall surfaces.
Eventually, the cream usually rises to the top, and it’s good to see new building code standards beginning to move this process along. Just realize that the way things are usually done isn’t always the best, at least as far as new walls go.