The Efficient Materials Trap

Efficient materials can sometimes seem to be the ideal path for green building. If we can find a way to more efficiently produce the materials we need to build our buildings, it would seem that we would be well on our way to reducing our impact on the planet.

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For example, rather than using lumber sawn from old growth forests, engineered lumber and I-joists make more efficient use of lumber resources and can take advantage of smaller trees. Instead of needing to find trees old enough and large enough to produce a piece of 2 x 12 lumber, an engineered I-joist can be made that uses chipped wood and glue manufactured wood board (like oriented strand board) and narrow, laminated strips of wood (again, made of smaller pieces of wood and glue). These engineered joists are lighter, straighter, and less prone to warping, cupping and twisting than even kiln dried sawn lumber is.

Engineered joists would seem to be an ideal solution. They are made from small, rapidly renewable trees, which can be farmed, rather than requiring the logging of large trees. Builders and carpenters like them because they are more regular, and they make for flatter floors, straighter walls, and truer roofs, with less variability when they are installed and less likelihood to move and twist over time.

But there are downsides to these more efficient materials.

While a house built with 2 x 12 floor joists may be able to be disassembled and those pieces of wood re-used, recovering engineered I-joists - which are more fragile - is a much harder task. It is much more likely that the engineered joists will end up in a landfill at the end of their life.

Efficiency also means that they are suited only for the purpose they are designed for. If you needed to cross a 15-foot wide stream, you could lay down a 2 x 12 on its side and walk across it; it would bend in the middle, but it would be strong enough to hold you even if it was lying on its side. An engineered wood I-joist of the same length, if laid on its side, would likely drop you in the water when you reached the middle; it doesn’t have any strength other than the direction in which it is designed to be used. So while it saves on material, it also reduces the flexibility with which it can be used.

Similarly, do highly efficient vehicles make it easier for people to do more driving? If even more people were driving fuel guzzling SUVs, the constricting supply and spiking prices for gasoline would be forcing even more people to take a closer look at their driving habits and trying to reduce their overall use.

The increase in efficiency has helped to make it possible to build the overblown tract houses that are sprawling across the landscape across the country. Without the development of these materials, lumber availability and costs would make it much harder to build the numbers of oversized houses at such relatively inexpensive prices. If solid sawn lumber was the only building material available, the growth of “lawyer foyer” houses (as one friend refers to them) would be much more constrained.

A little bit more efficiency sometimes becomes a license to be a lot more wasteful with the materials we consume. Efficiency can provide significant benefits, but alone, it is not the entire solution.

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