Home building in the U.S. could be on the verge of an energy savings and human comfort revolution, and it all has to do with how exterior walls are made now and two acronyms (AAC and SIPs) that point to a brighter future.

How walls are made now is simple: lots and lots of pieces. Think of the standard platform framing system wall with its 2-by-4s and 2-by-6s, headers, sill, plates, corner blocking, insulation; vapor barrier, exterior plywood panels, interior gypsum board (Sheetrock) panels, thousands of screws, nails, and other connectors, backer rods, caulking, adhesives, and paints. I am reminded of T. S. Eliot's poem "The Wasteland": "These fragments I have shored against my ruins."

And, indeed, what we get is not unlike ruins. These walls often leak air, water, and water vapor, and let heat out during winter months and heat in during summer months. The secret lurking here is that conventional walls are extraordinarily difficult—nearly impossible in real-world circumstances—to build well.

Imagine making a balloon by sewing bits of rubber together with twine and you will get a sense of the challenge. Every bit of lumber has to be perfectly straight, true, and square; every insulation edge has to fit perfectly against every adjacent surface; every overlap, joint, corner, and notch has to be virtually air tight.

Sustainable Building Blocks Aerated autoclaved concrete blocks (top) and structural insulated panels (bottom) are early-20th-century inventions resulting from a desire to put renewable resources to the greatest and best use in building walls where energy conservation and human comfort are tantamount.

On paper and in theory, all of this looks just fine; but with the inevitable warps and twists, nicks, gaps, open seams, and pin holes that occur in wall building, it just doesn't happen. So we don't get balloons; we get, in essence, creaking, racking sieves.

On to the acronyms: aerated autoclaved concrete (AAC) and structural insulated panels (SIPs). Of all the building technology in the market today, the ones that could have the largest, fastest, and most significant positive impacts are these modern, monolithic wall building systems. (Variations on these systems exist, but let's let these two be illustrative for the moment.)

Modern first: Both are early-20th-century inventions resulting from a desire to put renewable resources to the greatest and best use in building walls where energy conservation and human comfort are tantamount.

AAC was developed in Sweden in 1914 and is used for over 80 percent of the housing in Europe today. Essentially sand-based concrete mixed with aluminum powder, it starts out as a white, foamy, doughy mix that gets cut into shape and heated under pressure (autoclaved). Presto, change-o: You get a strong-as-normal-concrete product with millions of tiny air bubbles (aerated) that is super lightweight, thermally insulative, vapor permeable, waterproof, soundproof, bulletproof, and...it floats. Sold as blocks that are anywhere from 4 to 12 inches deep, 8 to 24 or more inches high, and 24 inches or more long, AAC can receive paint, plaster, stucco, gypsum board, brick, or other cladding—anything that a concrete wall can do, AAC can do as well or better. AAC cuts with a wood saw, can be carved, used to construct buildings six or seven stories high, and has floor plank spans of 20 feet and beyond. The joints are 1/8 inch or less and made with an adhesive mortar that is stronger than the block itself.

Hence, you have a monolithic (one-piece) wall system that doesn't significantly let air, water, water vapor, or heat in or out to a homeowner's disadvantage. Thermally (heat retention–wise), it's like a well-insulated balloon made of one piece of rubber, i.e., it doesn't leak. More important, it produces a home that stays comfortable for hours longer than a conventional building after it is heated or cooled, is whisper quiet, and cost effective to heat and cool.

Fast forward to the U.S. in 1930s: The U.S. Forestry Service has a flash of inspiration relative to promoting U.S. forestry products. It comes up with a sort of sandwich called a Structural Insulated Panel. That is, it makes a wall that acts like an I-beam, is capable of supporting tons of force (structural), is thermally efficient (insulated), and is available as a panel. SIPs, as they are generically known, comprise two outer layers of oriented strand board (OSB), plywood, or other skin (bullet-proof, anyone?) that are adhered to an inner layer of solid insulative foam (expanded polystyrene or EPS, extruded polystyrene, or polyurethane foams are typical). They are often 4 to 8 feet wide and 12 to 14 feet long, with a depth that typically varies between 4 5/8 inches to 6 5/8 inches. Their edges interlock and are made "air-tight" (various systems have been developed to achieve this), and they can be joined to each other and other building system components using screws or nails or other readily available connectors. In general they can achieve the same thermal efficiency as a conventional wall that is two to three times as thick, and, again, with virtually no leaks to or from the outside.

The fun part of SIPs is that they can be precut to virtually any size or shape you want (some manufacturers offer curved panels) and can be made directly from an architect's computer-generated design drawings. The house shows up on a flatbed truck as a kit of parts, with each wall section numbered like in a kid's game. Speed of assembly is fast, fast, fast: The rule of thumb is that a four-person crew can assemble a 2,400-square-foot house (exterior walls and roof) in four days. Here, also, we have our own home grown modern and monolithic building system, our stateside version of the Swedish AAC wall.

Surprisingly, perhaps, both AAC and SIPs are generally cost-comparable to conventional wood-framed buildings while outperforming them, and are readily available across most of the country. Both take a crew a couple of hours to learn, and need only one or two special tools in addition to a normal builder's tool kit. Both interact superbly with the latest and greatest air conditioning systems. And neither have significant negative energy or pollutant impacts. So why hasn't one monolithic wall system or other become the standard in the U.S. yet?

Well, our conventional platform framing system was developed in the 19th century when we Americans were expanding westward as fast as we could travel, and we needed a quick and cost-effective building system that could be easily learned and deployed just about anywhere. And to this day, a builder will tell you that we Americans can build houses faster and cheaper than anyone else on the planet.

And for years—years when dirt-cheap energy was abundant—that was great, and certainly good enough.

But now, the technologies we need for this century's better-performing, healthier buildings are ours, at reasonable costs, simply for the asking.