Structural Insulated Panels (SIPs) combine a core of insulating foam with outer layers or oriented strand board (OSB).
- Train yourself about zero energy construction or get trained people involved in the project as early as possible.
- Protect SIPs from damage. Stack the on site – dry and flat and off the ground, and organize them so they go up locally, that is panels on top of the stacks go up first.
- Get the right equipment for rigging and lifting heavy and awkward building components. A boom truck, for example, may be needed for heavy lifting, and specialized tools required for cutting panels where necessary.
- Make sure the foundation is accurate.
- Provide a drainage plan on both walls and roof to protect the panels from water damage.
- Minimizing air leaks is a primary goal, so know the details of connecting panels and running wires.
- Check drawing for accuracy and make sure that details on allowable spans are correct. Verify that point loads are adequately supported.
- Attach solar panels to the roof to minimize penetrations of the roof membrane. Here, clips for the panels were fastened to raised metal seams without disrupting the roof membrane and increasing the risk of leaks.
- A single ridge beam to support the roof panels makes construction faster. Plan the distribution of labor and arrange for a boom truck to get the job done quickly and safety.
- Devise a sound construction plan to match the resources that will be available, and make sure that all subcontractors understand what it is.
Autoclaved Aerated concrete (AAC)
Some builders have switched to blocks made from autoclaved aerated concrete (AAC). AAC blocks take the place of a number of components used in a standard stick frame—wood, insulation, house wrap, and drywall—all in a single product. The result is a house that’s fire-proof, mold-proof, insect resistant, hypoallergenic, sound-absorptive, and engineered to withstand hurricanes and earthquakes.
AAC is an interesting product. Aluminum power added to a mix of sand, lime, water and cement creates a five-fold increase in volume while trapping insulating air bubbles. It’s hardened in a mold and then processed in an autoclave to produce blocks 8 in. or 12 in. thick, 8 in. high, and 24 in. long. Blocks can be cut on-site with a specialized handsaw or band-saw and laid up somewhat like conventional concrete block.
Walls made with AAC block (Hebel is one trade name) have far less air infiltration than conventional 2×4 constructions, some builders say, with insulating values for the 8-in. block as high as R-21 (less in colder climates). Although building with AAC is more expensive than standard 2×4 construction, the company offsets higher costs in other ways to remain competitive with wood-framed houses.
Rastra – Insulated Concrete Form (ICF)
AAC blocks are not the only alternative. Rastra is a type of insulated concrete form (ICF) made mostly of recycled polystyrene with some cement to form a material the company calls “Thastyron.” It’s made into hollow-core blocks that are relatively lightweight, can be cut with ordinary handsaw, and glued into place. Once stacked into walls, the blocks are reinforced with steel and filled with concrete to form finished walls. The company reports that 10-in.-thick walls have an R-value of 36.
Durisol is yet another option. These hollow-core blocks are made from mineralized wood shavings and Portland cement, stacked into walls and then finished with reinforcing steel and concrete. The company says the material is noncombustible, sound absorptive, and dimensionally stable—and is made of 78% recycled content. It’s also 100% recyclable.
Products like these share many green benefits and give builders interested in exploring new avenues considerable leeway. They are not as widely available as wood building products and may make the most sense in areas with local or regional suppliers. One more consideration: there is a learning curve in working with new materials. Converts will tell you it’s well worth it.